# class IO

Expect library adds the `IO` instance method `expect`, which does similar act to tcl's expect extension.

In order to use this method, you must require expect:

    require 'expect'

Please see `expect` for usage.

The `IO` class is the basis for all input and output in Ruby. An I/O stream may be duplexed (that is, bidirectional), and so may use more than one native operating system stream.

Many of the examples in this section use the `File` class, the only standard subclass of `IO`. The two classes are closely associated. Like the `File` class, the `Socket` library subclasses from `IO` (such as `TCPSocket` or `UDPSocket`).

The `Kernel#open` method can create an `IO` (or `File`) object for these types of arguments:

- A plain string represents a filename suitable for the underlying operating system.

- A string starting with `"|"` indicates a subprocess. The remainder of the string following the `"|"` is invoked as a process with appropriate input/output channels connected to it.

- A string equal to `"|-"` will create another Ruby instance as a subprocess.

The `IO` may be opened with different file modes (read-only, write-only) and encodings for proper conversion. See `IO.new` for these options. See `Kernel#open` for details of the various command formats described above.

`IO.popen`, the `Open3` library, or Process#spawn may also be used to communicate with subprocesses through an `IO`.

Ruby will convert pathnames between different operating system conventions if possible. For instance, on a Windows system the filename `"/gumby/ruby/test.rb"` will be opened as `"\gumby\ruby\test.rb"`. When specifying a Windows-style filename in a Ruby string, remember to escape the backslashes:

    "C:\\gumby\\ruby\\test.rb"

Our examples here will use the Unix-style forward slashes; File::ALT_SEPARATOR can be used to get the platform-specific separator character.

The global constant `ARGF` (also accessible as `$<`) provides an IO-like stream which allows access to all files mentioned on the command line (or STDIN if no files are mentioned). `ARGF#path` and its alias `ARGF#filename` are provided to access the name of the file currently being read.

## io/console¶ ↑

The io/console extension provides methods for interacting with the console. The console can be accessed from `IO.console` or the standard input/output/error `IO` objects.

Requiring io/console adds the following methods:

- `IO::console`

- `IO#raw`

- `IO#raw!`

- `IO#cooked`

- `IO#cooked!`

- `IO#getch`

- `IO#echo=`

- `IO#echo?`

- `IO#noecho`

- `IO#winsize`

- `IO#winsize=`

- `IO#iflush`

- `IO#ioflush`

- `IO#oflush`

Example:

    require 'io/console'
    rows, columns = $stdout.winsize
    puts "Your screen is #{columns} wide and #{rows} tall"

### Constants

EWOULDBLOCKWaitReadable

  `EAGAINWaitReadable`

EWOULDBLOCKWaitWritable

  `EAGAINWaitWritable`

SEEK_CUR

  `Set` I/O position from the current position

SEEK_DATA

  `Set` I/O position to the next location containing data

SEEK_END

  `Set` I/O position from the end

SEEK_HOLE

  `Set` I/O position to the next hole

SEEK_SET

  `Set` I/O position from the beginning

### Public Class Methods

binread(name, [length [, offset]] ) → string click to toggle source

Opens the file, optionally seeks to the given offset, then returns length bytes (defaulting to the rest of the file). `binread` ensures the file is closed before returning. The open mode would be “rb:ASCII-8BIT”.

    IO.binread("testfile")           #=> "This is line one\nThis is line two\nThis is line three\nAnd so on...\n"
    IO.binread("testfile", 20)       #=> "This is line one\nThi"
    IO.binread("testfile", 20, 10)   #=> "ne one\nThis is line "

    static VALUE
    rb_io_s_binread(int argc, VALUE *argv, VALUE io)
    {
        VALUE offset;
        struct foreach_arg arg;
        enum {
            fmode = FMODE_READABLE|FMODE_BINMODE,
            oflags = O_RDONLY
    #ifdef O_BINARY
                    |O_BINARY
    #endif
        };
        convconfig_t convconfig = {NULL, NULL, 0, Qnil};

        rb_scan_args(argc, argv, "12", NULL, NULL, &offset);
        FilePathValue(argv[0]);
        convconfig.enc = rb_ascii8bit_encoding();
        arg.io = rb_io_open_generic(io, argv[0], oflags, fmode, &convconfig, 0);
        if (NIL_P(arg.io)) return Qnil;
        arg.argv = argv+1;
        arg.argc = (argc > 1) ? 1 : 0;
        if (!NIL_P(offset)) {
            struct seek_arg sarg;
            int state = 0;
            sarg.io = arg.io;
            sarg.offset = offset;
            sarg.mode = SEEK_SET;
            rb_protect(seek_before_access, (VALUE)&sarg, &state);
            if (state) {
                rb_io_close(arg.io);
                rb_jump_tag(state);
            }
        }
        return rb_ensure(io_s_read, (VALUE)&arg, rb_io_close, arg.io);
    }

binwrite(name, string, [offset] ) → integer click to toggle source
binwrite(name, string, [offset], open_args ) → integer

Same as `IO.write` except opening the file in binary mode and ASCII-8BIT encoding (“wb:ASCII-8BIT”).

    static VALUE
    rb_io_s_binwrite(int argc, VALUE *argv, VALUE io)
    {
        return io_s_write(argc, argv, io, 1);
    }

console → #<File:/dev/tty> click to toggle source
console(sym, *args)

Returns an `File` instance opened console.

If `sym` is given, it will be sent to the opened console with `args` and the result will be returned instead of the console `IO` itself.

You must require 'io/console' to use this method.

    static VALUE
    console_dev(int argc, VALUE *argv, VALUE klass)
    {
        VALUE con = 0;
        rb_io_t *fptr;
        VALUE sym = 0;

        rb_check_arity(argc, 0, UNLIMITED_ARGUMENTS);
        if (argc) {
            Check_Type(sym = argv[0], T_SYMBOL);
        }
        if (klass == rb_cIO) klass = rb_cFile;
        if (rb_const_defined(klass, id_console)) {
            con = rb_const_get(klass, id_console);
            if (!RB_TYPE_P(con, T_FILE) ||
                (!(fptr = RFILE(con)->fptr) || GetReadFD(fptr) == -1)) {
                rb_const_remove(klass, id_console);
                con = 0;
            }
        }
        if (sym) {
            if (sym == ID2SYM(id_close) && argc == 1) {
                if (con) {
                    rb_io_close(con);
                    rb_const_remove(klass, id_console);
                    con = 0;
                }
                return Qnil;
            }
        }
        if (!con) {
            VALUE args[2];
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H || defined HAVE_SGTTY_H
    # define CONSOLE_DEVICE "/dev/tty"
    #elif defined _WIN32
    # define CONSOLE_DEVICE "con$"
    # define CONSOLE_DEVICE_FOR_READING "conin$"
    # define CONSOLE_DEVICE_FOR_WRITING "conout$"
    #endif
    #ifndef CONSOLE_DEVICE_FOR_READING
    # define CONSOLE_DEVICE_FOR_READING CONSOLE_DEVICE
    #endif
    #ifdef CONSOLE_DEVICE_FOR_WRITING
            VALUE out;
            rb_io_t *ofptr;
    #endif
            int fd;

    #ifdef CONSOLE_DEVICE_FOR_WRITING
            fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_WRITING, O_RDWR, 0);
            if (fd < 0) return Qnil;
            rb_update_max_fd(fd);
            args[1] = INT2FIX(O_WRONLY);
            args[0] = INT2NUM(fd);
            out = rb_class_new_instance(2, args, klass);
    #endif
            fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_READING, O_RDWR, 0);
            if (fd < 0) {
    #ifdef CONSOLE_DEVICE_FOR_WRITING
                rb_io_close(out);
    #endif
                return Qnil;
            }
            rb_update_max_fd(fd);
            args[1] = INT2FIX(O_RDWR);
            args[0] = INT2NUM(fd);
            con = rb_class_new_instance(2, args, klass);
            GetOpenFile(con, fptr);
            fptr->pathv = rb_obj_freeze(rb_str_new2(CONSOLE_DEVICE));
    #ifdef CONSOLE_DEVICE_FOR_WRITING
            GetOpenFile(out, ofptr);
            ofptr->pathv = fptr->pathv;
            fptr->tied_io_for_writing = out;
            ofptr->mode |= FMODE_SYNC;
    #endif
            fptr->mode |= FMODE_SYNC;
            rb_const_set(klass, id_console, con);
        }
        if (sym) {
            return rb_f_send(argc, argv, con);
        }
        return con;
    }

copy_stream(src, dst) click to toggle source
copy_stream(src, dst, copy_length)
copy_stream(src, dst, copy_length, src_offset)

`IO.copy_stream` copies src to dst. src and dst is either a filename or an IO-like object. IO-like object for src should have `readpartial` or `read` method. IO-like object for dst should have `write` method. (Specialized mechanisms, such as sendfile system call, may be used on appropriate situation.)

This method returns the number of bytes copied.

If optional arguments are not given, the start position of the copy is the beginning of the filename or the current file offset of the `IO`. The end position of the copy is the end of file.

If copy_length is given, No more than copy_length bytes are copied.

If src_offset is given, it specifies the start position of the copy.

When src_offset is specified and src is an `IO`, `IO.copy_stream` doesn't move the current file offset.

    static VALUE
    rb_io_s_copy_stream(int argc, VALUE *argv, VALUE io)
    {
        VALUE src, dst, length, src_offset;
        struct copy_stream_struct st;

        MEMZERO(&st, struct copy_stream_struct, 1);

        rb_scan_args(argc, argv, "22", &src, &dst, &length, &src_offset);

        st.src = src;
        st.dst = dst;

        if (NIL_P(length))
            st.copy_length = (off_t)-1;
        else
            st.copy_length = NUM2OFFT(length);

        if (NIL_P(src_offset))
            st.src_offset = (off_t)-1;
        else
            st.src_offset = NUM2OFFT(src_offset);

        rb_ensure(copy_stream_body, (VALUE)&st, copy_stream_finalize, (VALUE)&st);

        return OFFT2NUM(st.total);
    }

for_fd(fd, mode [, opt]) → io click to toggle source

Synonym for `IO.new`.

    static VALUE
    rb_io_s_for_fd(int argc, VALUE *argv, VALUE klass)
    {
        VALUE io = rb_obj_alloc(klass);
        rb_io_initialize(argc, argv, io);
        return io;
    }

foreach(name, sep=$/ [, getline_args, open_args]) {|line| block } → nil click to toggle source
foreach(name, limit [, getline_args, open_args]) {|line| block } → nil
foreach(name, sep, limit [, getline_args, open_args]) {|line| block } → nil
foreach(...) → an_enumerator

Executes the block for every line in the named I/O port, where lines are separated by sep.

If no block is given, an enumerator is returned instead.

    IO.foreach("testfile") {|x| print "GOT ", x }

produces:

    GOT This is line one
    GOT This is line two
    GOT This is line three
    GOT And so on...

If the last argument is a hash, it's the keyword argument to open. See `IO.readlines` for details about getline_args. And see also `IO.read` for details about open_args.

    static VALUE
    rb_io_s_foreach(int argc, VALUE *argv, VALUE self)
    {
        VALUE opt;
        int orig_argc = argc;
        struct foreach_arg arg;
        struct getline_arg garg;

        argc = rb_scan_args(argc, argv, "13:", NULL, NULL, NULL, NULL, &opt);
        RETURN_ENUMERATOR(self, orig_argc, argv);
        extract_getline_args(argc-1, argv+1, &garg);
        open_key_args(self, argc, argv, opt, &arg);
        if (NIL_P(arg.io)) return Qnil;
        extract_getline_opts(opt, &garg);
        check_getline_args(&garg.rs, &garg.limit, garg.io = arg.io);
        return rb_ensure(io_s_foreach, (VALUE)&garg, rb_io_close, arg.io);
    }

new(fd [, mode] [, opt]) → io click to toggle source

Returns a new `IO` object (a stream) for the given integer file descriptor `fd` and `mode` string. `opt` may be used to specify parts of `mode` in a more readable fashion. See also `IO.sysopen` and `IO.for_fd`.

`IO.new` is called by various `File` and `IO` opening methods such as `IO::open`, `Kernel#open`, and `File::open`.

### Open Mode¶ ↑

When `mode` is an integer it must be combination of the modes defined in `File::Constants` (`File::RDONLY`, `File::WRONLY|File::CREAT`). See the open(2) man page for more information.

When `mode` is a string it must be in one of the following forms:

    fmode
    fmode ":" ext_enc
    fmode ":" ext_enc ":" int_enc
    fmode ":" "BOM|UTF-*"

`fmode` is an `IO` open mode string, `ext_enc` is the external encoding for the `IO` and `int_enc` is the internal encoding.

#### `IO` Open Mode¶ ↑

Ruby allows the following open modes:

    "r"  Read-only, starts at beginning of file  (default mode).

    "r+" Read-write, starts at beginning of file.

    "w"  Write-only, truncates existing file
         to zero length or creates a new file for writing.

    "w+" Read-write, truncates existing file to zero length
         or creates a new file for reading and writing.

    "a"  Write-only, each write call appends data at end of file.
         Creates a new file for writing if file does not exist.

    "a+" Read-write, each write call appends data at end of file.
         Creates a new file for reading and writing if file does
         not exist.

The following modes must be used separately, and along with one or more of the modes seen above.

    "b"  Binary file mode
         Suppresses EOL <-> CRLF conversion on Windows. And
         sets external encoding to ASCII-8BIT unless explicitly
         specified.

    "t"  Text file mode

The exclusive access mode (“x”) can be used together with “w” to ensure the file is created. `Errno::EEXIST` is raised when it already exists. It may not be supported with all kinds of streams (e.g. pipes).

When the open mode of original `IO` is read only, the mode cannot be changed to be writable. Similarly, the open mode cannot be changed from write only to readable.

When such a change is attempted the error is raised in different locations according to the platform.

### `IO` `Encoding`¶ ↑

When `ext_enc` is specified, strings read will be tagged by the encoding when reading, and strings output will be converted to the specified encoding when writing.

When `ext_enc` and `int_enc` are specified read strings will be converted from `ext_enc` to `int_enc` upon input, and written strings will be converted from `int_enc` to `ext_enc` upon output. See `Encoding` for further details of transcoding on input and output.

If “BOM|UTF-8”, “BOM|UTF-16LE” or “BOM|UTF16-BE” are used, Ruby checks for a Unicode BOM in the input document to help determine the encoding. For UTF-16 encodings the file open mode must be binary. When present, the BOM is stripped and the external encoding from the BOM is used. When the BOM is missing the given Unicode encoding is used as `ext_enc`. (The BOM-set encoding option is case insensitive, so “bom|utf-8” is also valid.)

### Options¶ ↑

`opt` can be used instead of `mode` for improved readability. The following keys are supported:

:mode

  Same as `mode` parameter

:flags

  Specifies file open flags as integer. If `mode` parameter is given, this parameter will be bitwise-ORed.

:external_encoding

  External encoding for the `IO`.

:internal_encoding

  Internal encoding for the `IO`. “-” is a synonym for the default internal encoding.

  If the value is `nil` no conversion occurs.

:encoding

  Specifies external and internal encodings as “extern:intern”.

:textmode

  If the value is truth value, same as “t” in argument `mode`.

:binmode

  If the value is truth value, same as “b” in argument `mode`.

:autoclose

  If the value is `false`, the `fd` will be kept open after this `IO` instance gets finalized.

Also, `opt` can have same keys in `String#encode` for controlling conversion between the external encoding and the internal encoding.

### Example 1¶ ↑

    fd = IO.sysopen("/dev/tty", "w")
    a = IO.new(fd,"w")
    $stderr.puts "Hello"
    a.puts "World"

Produces:

    Hello
    World

### Example 2¶ ↑

    require 'fcntl'

    fd = STDERR.fcntl(Fcntl::F_DUPFD)
    io = IO.new(fd, mode: 'w:UTF-16LE', cr_newline: true)
    io.puts "Hello, World!"

    fd = STDERR.fcntl(Fcntl::F_DUPFD)
    io = IO.new(fd, mode: 'w', cr_newline: true,
                external_encoding: Encoding::UTF_16LE)
    io.puts "Hello, World!"

Both of above print “Hello, World!” in UTF-16LE to standard error output with converting EOL generated by `puts` to CR.

    static VALUE
    rb_io_initialize(int argc, VALUE *argv, VALUE io)
    {
        VALUE fnum, vmode;
        rb_io_t *fp;
        int fd, fmode, oflags = O_RDONLY;
        convconfig_t convconfig;
        VALUE opt;
    #if defined(HAVE_FCNTL) && defined(F_GETFL)
        int ofmode;
    #else
        struct stat st;
    #endif

        argc = rb_scan_args(argc, argv, "11:", &fnum, &vmode, &opt);
        rb_io_extract_modeenc(&vmode, 0, opt, &oflags, &fmode, &convconfig);

        fd = NUM2INT(fnum);
        if (rb_reserved_fd_p(fd)) {
            rb_raise(rb_eArgError, "The given fd is not accessible because RubyVM reserves it");
        }
    #if defined(HAVE_FCNTL) && defined(F_GETFL)
        oflags = fcntl(fd, F_GETFL);
        if (oflags == -1) rb_sys_fail(0);
    #else
        if (fstat(fd, &st) < 0) rb_sys_fail(0);
    #endif
        rb_update_max_fd(fd);
    #if defined(HAVE_FCNTL) && defined(F_GETFL)
        ofmode = rb_io_oflags_fmode(oflags);
        if (NIL_P(vmode)) {
            fmode = ofmode;
        }
        else if ((~ofmode & fmode) & FMODE_READWRITE) {
            VALUE error = INT2FIX(EINVAL);
            rb_exc_raise(rb_class_new_instance(1, &error, rb_eSystemCallError));
        }
    #endif
        if (!NIL_P(opt) && rb_hash_aref(opt, sym_autoclose) == Qfalse) {
            fmode |= FMODE_PREP;
        }
        MakeOpenFile(io, fp);
        fp->fd = fd;
        fp->mode = fmode;
        fp->encs = convconfig;
        clear_codeconv(fp);
        io_check_tty(fp);
        if (fileno(stdin) == fd)
            fp->stdio_file = stdin;
        else if (fileno(stdout) == fd)
            fp->stdio_file = stdout;
        else if (fileno(stderr) == fd)
            fp->stdio_file = stderr;

        if (fmode & FMODE_SETENC_BY_BOM) io_set_encoding_by_bom(io);
        return io;
    }

open(fd, mode="r" [, opt]) → io click to toggle source
open(fd, mode="r" [, opt]) {|io| block } → obj

With no associated block, `IO.open` is a synonym for `IO.new`. If the optional code block is given, it will be passed `io` as an argument, and the `IO` object will automatically be closed when the block terminates. In this instance, `IO.open` returns the value of the block.

See `IO.new` for a description of the `fd`, `mode` and `opt` parameters.

    static VALUE
    rb_io_s_open(int argc, VALUE *argv, VALUE klass)
    {
        VALUE io = rb_class_new_instance(argc, argv, klass);

        if (rb_block_given_p()) {
            return rb_ensure(rb_yield, io, io_close, io);
        }

        return io;
    }

pipe → [read_io, write_io] click to toggle source
pipe(ext_enc) → [read_io, write_io]
pipe("ext_enc:int_enc" [, opt]) → [read_io, write_io]
pipe(ext_enc, int_enc [, opt]) → [read_io, write_io]
pipe(...) {|read_io, write_io| ... }

Creates a pair of pipe endpoints (connected to each other) and returns them as a two-element array of `IO` objects: `[` read_io, write_io `]`.

If a block is given, the block is called and returns the value of the block. read_io and write_io are sent to the block as arguments. If read_io and write_io are not closed when the block exits, they are closed. i.e. closing read_io and/or write_io doesn't cause an error.

Not available on all platforms.

If an encoding (encoding name or encoding object) is specified as an optional argument, read string from pipe is tagged with the encoding specified. If the argument is a colon separated two encoding names “A:B”, the read string is converted from encoding A (external encoding) to encoding B (internal encoding), then tagged with B. If two optional arguments are specified, those must be encoding objects or encoding names, and the first one is the external encoding, and the second one is the internal encoding. If the external encoding and the internal encoding is specified, optional hash argument specify the conversion option.

In the example below, the two processes close the ends of the pipe that they are not using. This is not just a cosmetic nicety. The read end of a pipe will not generate an end of file condition if there are any writers with the pipe still open. In the case of the parent process, the `rd.read` will never return if it does not first issue a `wr.close`.

    rd, wr = IO.pipe

    if fork
      wr.close
      puts "Parent got: <#{rd.read}>"
      rd.close
      Process.wait
    else
      rd.close
      puts "Sending message to parent"
      wr.write "Hi Dad"
      wr.close
    end

produces:

    Sending message to parent
    Parent got: <Hi Dad>

    static VALUE
    rb_io_s_pipe(int argc, VALUE *argv, VALUE klass)
    {
        int pipes[2], state;
        VALUE r, w, args[3], v1, v2;
        VALUE opt;
        rb_io_t *fptr, *fptr2;
        struct io_encoding_set_args ies_args;
        int fmode = 0;
        VALUE ret;

        argc = rb_scan_args(argc, argv, "02:", &v1, &v2, &opt);
        if (rb_pipe(pipes) < 0)
            rb_sys_fail(0);

        args[0] = klass;
        args[1] = INT2NUM(pipes[0]);
        args[2] = INT2FIX(O_RDONLY);
        r = rb_protect(io_new_instance, (VALUE)args, &state);
        if (state) {
            close(pipes[0]);
            close(pipes[1]);
            rb_jump_tag(state);
        }
        GetOpenFile(r, fptr);

        ies_args.fptr = fptr;
        ies_args.v1 = v1;
        ies_args.v2 = v2;
        ies_args.opt = opt;
        rb_protect(io_encoding_set_v, (VALUE)&ies_args, &state);
        if (state) {
            close(pipes[1]);
            io_close(r);
            rb_jump_tag(state);
        }

        args[1] = INT2NUM(pipes[1]);
        args[2] = INT2FIX(O_WRONLY);
        w = rb_protect(io_new_instance, (VALUE)args, &state);
        if (state) {
            close(pipes[1]);
            if (!NIL_P(r)) rb_io_close(r);
            rb_jump_tag(state);
        }
        GetOpenFile(w, fptr2);
        rb_io_synchronized(fptr2);

        extract_binmode(opt, &fmode);
    #if DEFAULT_TEXTMODE
        if ((fptr->mode & FMODE_TEXTMODE) && (fmode & FMODE_BINMODE)) {
            fptr->mode &= ~FMODE_TEXTMODE;
            setmode(fptr->fd, O_BINARY);
        }
    #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
        if (fptr->encs.ecflags & ECONV_DEFAULT_NEWLINE_DECORATOR) {
            fptr->encs.ecflags |= ECONV_UNIVERSAL_NEWLINE_DECORATOR;
        }
    #endif
    #endif
        fptr->mode |= fmode;
    #if DEFAULT_TEXTMODE
        if ((fptr2->mode & FMODE_TEXTMODE) && (fmode & FMODE_BINMODE)) {
            fptr2->mode &= ~FMODE_TEXTMODE;
            setmode(fptr2->fd, O_BINARY);
        }
    #endif
        fptr2->mode |= fmode;

        ret = rb_assoc_new(r, w);
        if (rb_block_given_p()) {
            VALUE rw[2];
            rw[0] = r;
            rw[1] = w;
            return rb_ensure(rb_yield, ret, pipe_pair_close, (VALUE)rw);
        }
        return ret;
    }

popen([env,] cmd, mode="r" [, opt]) → io click to toggle source
popen([env,] cmd, mode="r" [, opt]) {|io| block } → obj

Runs the specified command as a subprocess; the subprocess's standard input and output will be connected to the returned `IO` object.

The PID of the started process can be obtained by `IO#pid` method.

cmd is a string or an array as follows.

    cmd:
      "-"                                      : fork
      commandline                              : command line string which is passed to a shell
      [env, cmdname, arg1, ..., opts]          : command name and zero or more arguments (no shell)
      [env, [cmdname, argv0], arg1, ..., opts] : command name, argv[0] and zero or more arguments (no shell)
    (env and opts are optional.)

If cmd is a `String` “`-`'', then a new instance of Ruby is started as the subprocess.

If cmd is an `Array` of `String`, then it will be used as the subprocess's `argv` bypassing a shell. The array can contain a hash at first for environments and a hash at last for options similar to `spawn`.

The default mode for the new file object is “r'', but mode may be set to any of the modes listed in the description for class `IO`. The last argument opt qualifies mode.

    # set IO encoding
    IO.popen("nkf -e filename", :external_encoding=>"EUC-JP") {|nkf_io|
      euc_jp_string = nkf_io.read
    }

    # merge standard output and standard error using
    # spawn option.  See the document of Kernel.spawn.
    IO.popen(["ls", "/", :err=>[:child, :out]]) {|ls_io|
      ls_result_with_error = ls_io.read
    }

    # spawn options can be mixed with IO options
    IO.popen(["ls", "/"], :err=>[:child, :out]) {|ls_io|
      ls_result_with_error = ls_io.read
    }

Raises exceptions which `IO.pipe` and `Kernel.spawn` raise.

If a block is given, Ruby will run the command as a child connected to Ruby with a pipe. Ruby's end of the pipe will be passed as a parameter to the block. At the end of block, Ruby closes the pipe and sets `$?`. In this case `IO.popen` returns the value of the block.

If a block is given with a cmd of “`-`'', the block will be run in two separate processes: once in the parent, and once in a child. The parent process will be passed the pipe object as a parameter to the block, the child version of the block will be passed `nil`, and the child's standard in and standard out will be connected to the parent through the pipe. Not available on all platforms.

    f = IO.popen("uname")
    p f.readlines
    f.close
    puts "Parent is #{Process.pid}"
    IO.popen("date") {|f| puts f.gets }
    IO.popen("-") {|f| $stderr.puts "#{Process.pid} is here, f is #{f.inspect}"}
    p $?
    IO.popen(%w"sed -e s|^|<foo>| -e s&$&;zot;&", "r+") {|f|
      f.puts "bar"; f.close_write; puts f.gets
    }

produces:

    ["Linux\n"]
    Parent is 21346
    Thu Jan 15 22:41:19 JST 2009
    21346 is here, f is #<IO:fd 3>
    21352 is here, f is nil
    #<Process::Status: pid 21352 exit 0>
    <foo>bar;zot;

    static VALUE
    rb_io_s_popen(int argc, VALUE *argv, VALUE klass)
    {
        const char *modestr;
        VALUE pname, pmode = Qnil, port, tmp, opt = Qnil, env = Qnil, execarg_obj = Qnil;
        int oflags, fmode;
        convconfig_t convconfig;

        if (argc > 1 && !NIL_P(opt = rb_check_hash_type(argv[argc-1]))) --argc;
        if (argc > 1 && !NIL_P(env = rb_check_hash_type(argv[0]))) --argc, ++argv;
        switch (argc) {
          case 2:
            pmode = argv[1];
          case 1:
            pname = argv[0];
            break;
          default:
            {
                int ex = !NIL_P(opt);
                rb_error_arity(argc + ex, 1 + ex, 2 + ex);
            }
        }

        tmp = rb_check_array_type(pname);
        if (!NIL_P(tmp)) {
            long len = RARRAY_LEN(tmp);
    #if SIZEOF_LONG > SIZEOF_INT
            if (len > INT_MAX) {
                rb_raise(rb_eArgError, "too many arguments");
            }
    #endif
            execarg_obj = rb_execarg_new((int)len, RARRAY_CONST_PTR(tmp), FALSE, FALSE);
            RB_GC_GUARD(tmp);
        }
        else {
            SafeStringValue(pname);
            execarg_obj = Qnil;
            if (!is_popen_fork(pname))
                execarg_obj = rb_execarg_new(1, &pname, TRUE, FALSE);
        }
        if (!NIL_P(execarg_obj)) {
            if (!NIL_P(opt))
                opt = rb_execarg_extract_options(execarg_obj, opt);
            if (!NIL_P(env))
                rb_execarg_setenv(execarg_obj, env);
        }
        rb_io_extract_modeenc(&pmode, 0, opt, &oflags, &fmode, &convconfig);
        modestr = rb_io_oflags_modestr(oflags);

        port = pipe_open(execarg_obj, modestr, fmode, &convconfig);
        if (NIL_P(port)) {
            /* child */
            if (rb_block_given_p()) {
                rb_yield(Qnil);
                rb_io_flush(rb_stdout);
                rb_io_flush(rb_stderr);
                _exit(0);
            }
            return Qnil;
        }
        RBASIC_SET_CLASS(port, klass);
        if (rb_block_given_p()) {
            return rb_ensure(rb_yield, port, pipe_close, port);
        }
        return port;
    }

read(name, [length [, offset]] [, opt] ) → string click to toggle source

Opens the file, optionally seeks to the given `offset`, then returns `length` bytes (defaulting to the rest of the file). `read` ensures the file is closed before returning.

If `name` starts with a pipe character (`"|"`), a subprocess is created in the same way as `Kernel#open`, and its output is returned.

### Options¶ ↑

The options hash accepts the following keys:

:encoding

  string or encoding

  Specifies the encoding of the read string. `:encoding` will be ignored if `length` is specified. See `Encoding.aliases` for possible encodings.

:mode

  string or integer

  Specifies the mode argument for open(). It must start with an “r”, otherwise it will cause an error. See `IO.new` for the list of possible modes.

:open_args

  array

  Specifies arguments for open() as an array. This key can not be used in combination with either `:encoding` or `:mode`.

Examples:

    IO.read("testfile")              #=> "This is line one\nThis is line two\nThis is line three\nAnd so on...\n"
    IO.read("testfile", 20)          #=> "This is line one\nThi"
    IO.read("testfile", 20, 10)      #=> "ne one\nThis is line "
    IO.read("binfile", mode: "rb")   #=> "\xF7\x00\x00\x0E\x12"

    static VALUE
    rb_io_s_read(int argc, VALUE *argv, VALUE io)
    {
        VALUE opt, offset;
        struct foreach_arg arg;

        argc = rb_scan_args(argc, argv, "13:", NULL, NULL, &offset, NULL, &opt);
        open_key_args(io, argc, argv, opt, &arg);
        if (NIL_P(arg.io)) return Qnil;
        if (!NIL_P(offset)) {
            struct seek_arg sarg;
            int state = 0;
            sarg.io = arg.io;
            sarg.offset = offset;
            sarg.mode = SEEK_SET;
            rb_protect(seek_before_access, (VALUE)&sarg, &state);
            if (state) {
                rb_io_close(arg.io);
                rb_jump_tag(state);
            }
            if (arg.argc == 2) arg.argc = 1;
        }
        return rb_ensure(io_s_read, (VALUE)&arg, rb_io_close, arg.io);
    }

readlines(name, sep=$/ [, getline_args, open_args]) → array click to toggle source
readlines(name, limit [, getline_args, open_args]) → array
readlines(name, sep, limit [, getline_args, open_args]) → array

Reads the entire file specified by name as individual lines, and returns those lines in an array. Lines are separated by sep.

    a = IO.readlines("testfile")
    a[0]   #=> "This is line one\n"

    b = IO.readlines("testfile", chomp: true)
    b[0]   #=> "This is line one"

If the last argument is a hash, it's the keyword argument to open.

### Options for getline¶ ↑

The options hash accepts the following keys:

:chomp

  When the optional `chomp` keyword argument has a true value, `\n`, `\r`, and `\r\n` will be removed from the end of each line.

See also `IO.read` for details about open_args.

    static VALUE
    rb_io_s_readlines(int argc, VALUE *argv, VALUE io)
    {
        VALUE opt;
        struct foreach_arg arg;
        struct getline_arg garg;

        argc = rb_scan_args(argc, argv, "13:", NULL, NULL, NULL, NULL, &opt);
        extract_getline_args(argc-1, argv+1, &garg);
        open_key_args(io, argc, argv, opt, &arg);
        if (NIL_P(arg.io)) return Qnil;
        extract_getline_opts(opt, &garg);
        check_getline_args(&garg.rs, &garg.limit, garg.io = arg.io);
        return rb_ensure(io_s_readlines, (VALUE)&garg, rb_io_close, arg.io);
    }

select(read_array [, write_array [, error_array [, timeout]]]) → array or nil click to toggle source

Calls select(2) system call. It monitors given arrays of `IO` objects, waits until one or more of `IO` objects are ready for reading, are ready for writing, and have pending exceptions respectively, and returns an array that contains arrays of those `IO` objects. It will return `nil` if optional timeout value is given and no `IO` object is ready in timeout seconds.

`IO.select` peeks the buffer of `IO` objects for testing readability. If the `IO` buffer is not empty, `IO.select` immediately notifies readability. This “peek” only happens for `IO` objects. It does not happen for IO-like objects such as `OpenSSL::SSL::SSLSocket`.

The best way to use `IO.select` is invoking it after nonblocking methods such as `read_nonblock`, `write_nonblock`, etc. The methods raise an exception which is extended by `IO::WaitReadable` or `IO::WaitWritable`. The modules notify how the caller should wait with `IO.select`. If `IO::WaitReadable` is raised, the caller should wait for reading. If `IO::WaitWritable` is raised, the caller should wait for writing.

So, blocking read (`readpartial`) can be emulated using `read_nonblock` and `IO.select` as follows:

    begin
      result = io_like.read_nonblock(maxlen)
    rescue IO::WaitReadable
      IO.select([io_like])
      retry
    rescue IO::WaitWritable
      IO.select(nil, [io_like])
      retry
    end

Especially, the combination of nonblocking methods and `IO.select` is preferred for `IO` like objects such as `OpenSSL::SSL::SSLSocket`. It has `to_io` method to return underlying `IO` object. `IO.select` calls `to_io` to obtain the file descriptor to wait.

This means that readability notified by `IO.select` doesn't mean readability from `OpenSSL::SSL::SSLSocket` object.

The most likely situation is that `OpenSSL::SSL::SSLSocket` buffers some data. `IO.select` doesn't see the buffer. So `IO.select` can block when `OpenSSL::SSL::SSLSocket#readpartial` doesn't block.

However, several more complicated situations exist.

SSL is a protocol which is sequence of records. The record consists of multiple bytes. So, the remote side of SSL sends a partial record, `IO.select` notifies readability but `OpenSSL::SSL::SSLSocket` cannot decrypt a byte and `OpenSSL::SSL::SSLSocket#readpartial` will block.

Also, the remote side can request SSL renegotiation which forces the local SSL engine to write some data. This means `OpenSSL::SSL::SSLSocket#readpartial` may invoke `write` system call and it can block. In such a situation, `OpenSSL::SSL::SSLSocket#read_nonblock` raises `IO::WaitWritable` instead of blocking. So, the caller should wait for ready for writability as above example.

The combination of nonblocking methods and `IO.select` is also useful for streams such as tty, pipe socket socket when multiple processes read from a stream.

Finally, Linux kernel developers don't guarantee that readability of select(2) means readability of following read(2) even for a single process. See select(2) manual on GNU/Linux system.

Invoking `IO.select` before `IO#readpartial` works well as usual. However it is not the best way to use `IO.select`.

The writability notified by select(2) doesn't show how many bytes are writable. `IO#write` method blocks until given whole string is written. So, `IO#write(two or more bytes)` can block after writability is notified by `IO.select`. `IO#write_nonblock` is required to avoid the blocking.

Blocking write (`write`) can be emulated using `write_nonblock` and `IO.select` as follows: `IO::WaitReadable` should also be rescued for SSL renegotiation in `OpenSSL::SSL::SSLSocket`.

    while 0 < string.bytesize
      begin
        written = io_like.write_nonblock(string)
      rescue IO::WaitReadable
        IO.select([io_like])
        retry
      rescue IO::WaitWritable
        IO.select(nil, [io_like])
        retry
      end
      string = string.byteslice(written..-1)
    end

### Parameters¶ ↑

read_array

  an array of `IO` objects that wait until ready for read

write_array

  an array of `IO` objects that wait until ready for write

error_array

  an array of `IO` objects that wait for exceptions

timeout

  a numeric value in second

### Example¶ ↑

    rp, wp = IO.pipe
    mesg = "ping "
    100.times {
      # IO.select follows IO#read.  Not the best way to use IO.select.
      rs, ws, = IO.select([rp], [wp])
      if r = rs[0]
        ret = r.read(5)
        print ret
        case ret
        when /ping/
          mesg = "pong\n"
        when /pong/
          mesg = "ping "
        end
      end
      if w = ws[0]
        w.write(mesg)
      end
    }

produces:

    ping pong
    ping pong
    ping pong
    (snipped)
    ping

    static VALUE
    rb_f_select(int argc, VALUE *argv, VALUE obj)
    {
        VALUE timeout;
        struct select_args args;
        struct timeval timerec;
        int i;

        rb_scan_args(argc, argv, "13", &args.read, &args.write, &args.except, &timeout);
        if (NIL_P(timeout)) {
            args.timeout = 0;
        }
        else {
            timerec = rb_time_interval(timeout);
            args.timeout = &timerec;
        }

        for (i = 0; i < numberof(args.fdsets); ++i)
            rb_fd_init(&args.fdsets[i]);

        return rb_ensure(select_call, (VALUE)&args, select_end, (VALUE)&args);
    }

sysopen(path, [mode, [perm]]) → integer click to toggle source

Opens the given path, returning the underlying file descriptor as a `Integer`.

    IO.sysopen("testfile")   #=> 3

    static VALUE
    rb_io_s_sysopen(int argc, VALUE *argv)
    {
        VALUE fname, vmode, vperm;
        VALUE intmode;
        int oflags, fd;
        mode_t perm;

        rb_scan_args(argc, argv, "12", &fname, &vmode, &vperm);
        FilePathValue(fname);

        if (NIL_P(vmode))
            oflags = O_RDONLY;
        else if (!NIL_P(intmode = rb_check_to_integer(vmode, "to_int")))
            oflags = NUM2INT(intmode);
        else {
            SafeStringValue(vmode);
            oflags = rb_io_modestr_oflags(StringValueCStr(vmode));
        }
        if (NIL_P(vperm)) perm = 0666;
        else              perm = NUM2MODET(vperm);

        RB_GC_GUARD(fname) = rb_str_new4(fname);
        fd = rb_sysopen(fname, oflags, perm);
        return INT2NUM(fd);
    }

try_convert(obj) → io or nil click to toggle source

Try to convert obj into an `IO`, using `to_io` method. Returns converted `IO` or `nil` if obj cannot be converted for any reason.

    IO.try_convert(STDOUT)     #=> STDOUT
    IO.try_convert("STDOUT")   #=> nil

    require 'zlib'
    f = open("/tmp/zz.gz")       #=> #<File:/tmp/zz.gz>
    z = Zlib::GzipReader.open(f) #=> #<Zlib::GzipReader:0x81d8744>
    IO.try_convert(z)            #=> #<File:/tmp/zz.gz>

    static VALUE
    rb_io_s_try_convert(VALUE dummy, VALUE io)
    {
        return rb_io_check_io(io);
    }

write(name, string [, offset]) → integer click to toggle source
write(name, string [, offset] [, opt]) → integer

Opens the file, optionally seeks to the given offset, writes string, then returns the length written. `write` ensures the file is closed before returning. If offset is not given in write mode, the file is truncated. Otherwise, it is not truncated.

    IO.write("testfile", "0123456789", 20)  #=> 10
    # File could contain:  "This is line one\nThi0123456789two\nThis is line three\nAnd so on...\n"
    IO.write("testfile", "0123456789")      #=> 10
    # File would now read: "0123456789"

If the last argument is a hash, it specifies options for the internal open(). It accepts the following keys:

:encoding

  string or encoding

  Specifies the encoding of the read string. See `Encoding.aliases` for possible encodings.

:mode

  string or integer

  Specifies the mode argument for open(). It must start with “w”, “a”, or “r+”, otherwise it will cause an error. See `IO.new` for the list of possible modes.

:perm

  integer

  Specifies the perm argument for open().

:open_args

  array

  Specifies arguments for open() as an array. This key can not be used in combination with other keys.

    static VALUE
    rb_io_s_write(int argc, VALUE *argv, VALUE io)
    {
        return io_s_write(argc, argv, io, 0);
    }

### Public Instance Methods

ios << obj → ios click to toggle source

`String` Output—Writes obj to ios. obj will be converted to a string using `to_s`.

    $stdout << "Hello " << "world!\n"

produces:

    Hello world!

    VALUE
    rb_io_addstr(VALUE io, VALUE str)
    {
        rb_io_write(io, str);
        return io;
    }

advise(advice, offset=0, len=0) → nil click to toggle source

Announce an intention to access data from the current file in a specific pattern. On platforms that do not support the posix_fadvise(2) system call, this method is a no-op.

advice is one of the following symbols:

:normal

  No advice to give; the default assumption for an open file.

:sequential

  The data will be accessed sequentially with lower offsets read before higher ones.

:random

  The data will be accessed in random order.

:willneed

  The data will be accessed in the near future.

:dontneed

  The data will not be accessed in the near future.

:noreuse

  The data will only be accessed once.

The semantics of a piece of advice are platform-dependent. See man 2 posix_fadvise for details.

“data” means the region of the current file that begins at offset and extends for len bytes. If len is 0, the region ends at the last byte of the file. By default, both offset and len are 0, meaning that the advice applies to the entire file.

If an error occurs, one of the following exceptions will be raised:

`IOError`

  The `IO` stream is closed.

`Errno::EBADF`

  The file descriptor of the current file is invalid.

`Errno::EINVAL`

  An invalid value for advice was given.

`Errno::ESPIPE`

  The file descriptor of the current file refers to a FIFO or pipe. (Linux raises `Errno::EINVAL` in this case).

`TypeError`

  Either advice was not a `Symbol`, or one of the other arguments was not an `Integer`.

`RangeError`

  One of the arguments given was too big/small.

This list is not exhaustive; other `Errno`

  exceptions are also possible.

    static VALUE
    rb_io_advise(int argc, VALUE *argv, VALUE io)
    {
        VALUE advice, offset, len;
        off_t off, l;
        rb_io_t *fptr;

        rb_scan_args(argc, argv, "12", &advice, &offset, &len);
        advice_arg_check(advice);

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);

        off = NIL_P(offset) ? 0 : NUM2OFFT(offset);
        l   = NIL_P(len)    ? 0 : NUM2OFFT(len);

    #ifdef HAVE_POSIX_FADVISE
        return do_io_advise(fptr, advice, off, l);
    #else
        ((void)off, (void)l);       /* Ignore all hint */
        return Qnil;
    #endif
    }

autoclose = bool → true or false click to toggle source

Sets auto-close flag.

    f = open("/dev/null")
    IO.for_fd(f.fileno)
    # ...
    f.gets # may cause IOError

    f = open("/dev/null")
    IO.for_fd(f.fileno).autoclose = true
    # ...
    f.gets # won't cause IOError

    static VALUE
    rb_io_set_autoclose(VALUE io, VALUE autoclose)
    {
        rb_io_t *fptr;
        GetOpenFile(io, fptr);
        if (!RTEST(autoclose))
            fptr->mode |= FMODE_PREP;
        else
            fptr->mode &= ~FMODE_PREP;
        return io;
    }

autoclose? → true or false click to toggle source

Returns `true` if the underlying file descriptor of ios will be closed automatically at its finalization, otherwise `false`.

    static VALUE
    rb_io_autoclose_p(VALUE io)
    {
        rb_io_t *fptr = RFILE(io)->fptr;
        rb_io_check_closed(fptr);
        return (fptr->mode & FMODE_PREP) ? Qfalse : Qtrue;
    }

beep() click to toggle source

    static VALUE
    console_beep(VALUE io)
    {
        rb_io_t *fptr;
        int fd;

        GetOpenFile(io, fptr);
        fd = GetWriteFD(fptr);
    #ifdef _WIN32
        (void)fd;
        MessageBeep(0);
    #else
        if (write(fd, "\a", 1) < 0)
            rb_sys_fail(0);
    #endif
        return io;
    }

binmode → ios click to toggle source

Puts ios into binary mode. Once a stream is in binary mode, it cannot be reset to nonbinary mode.

- newline conversion disabled

- encoding conversion disabled

- content is treated as ASCII-8BIT

    static VALUE
    rb_io_binmode_m(VALUE io)
    {
        VALUE write_io;

        rb_io_ascii8bit_binmode(io);

        write_io = GetWriteIO(io);
        if (write_io != io)
            rb_io_ascii8bit_binmode(write_io);
        return io;
    }

binmode? → true or false click to toggle source

Returns `true` if ios is binmode.

    static VALUE
    rb_io_binmode_p(VALUE io)
    {
        rb_io_t *fptr;
        GetOpenFile(io, fptr);
        return fptr->mode & FMODE_BINMODE ? Qtrue : Qfalse;
    }

bytes() click to toggle source

This is a deprecated alias for `each_byte`.

    static VALUE
    rb_io_bytes(VALUE io)
    {
        rb_warn("IO#bytes is deprecated; use #each_byte instead");
        if (!rb_block_given_p())
            return rb_enumeratorize(io, ID2SYM(rb_intern("each_byte")), 0, 0);
        return rb_io_each_byte(io);
    }

chars() click to toggle source

This is a deprecated alias for `each_char`.

    static VALUE
    rb_io_chars(VALUE io)
    {
        rb_warn("IO#chars is deprecated; use #each_char instead");
        if (!rb_block_given_p())
            return rb_enumeratorize(io, ID2SYM(rb_intern("each_char")), 0, 0);
        return rb_io_each_char(io);
    }

close → nil click to toggle source

Closes ios and flushes any pending writes to the operating system. The stream is unavailable for any further data operations; an `IOError` is raised if such an attempt is made. I/O streams are automatically closed when they are claimed by the garbage collector.

If ios is opened by `IO.popen`, `close` sets `$?`.

Calling this method on closed `IO` object is just ignored since Ruby 2.3.

    static VALUE
    rb_io_close_m(VALUE io)
    {
        rb_io_t *fptr = rb_io_get_fptr(io);
        if (fptr->fd < 0) {
            return Qnil;
        }
        rb_io_close(io);
        return Qnil;
    }

close_on_exec = bool → true or false click to toggle source

Sets a close-on-exec flag.

    f = open("/dev/null")
    f.close_on_exec = true
    system("cat", "/proc/self/fd/#{f.fileno}") # cat: /proc/self/fd/3: No such file or directory
    f.closed?                #=> false

Ruby sets close-on-exec flags of all file descriptors by default since Ruby 2.0.0. So you don't need to set by yourself. Also, unsetting a close-on-exec flag can cause file descriptor leak if another thread use fork() and exec() (via system() method for example). If you really needs file descriptor inheritance to child process, use spawn()'s argument such as fd=>fd.

    static VALUE
    rb_io_set_close_on_exec(VALUE io, VALUE arg)
    {
        int flag = RTEST(arg) ? FD_CLOEXEC : 0;
        rb_io_t *fptr;
        VALUE write_io;
        int fd, ret;

        write_io = GetWriteIO(io);
        if (io != write_io) {
            GetOpenFile(write_io, fptr);
            if (fptr && 0 <= (fd = fptr->fd)) {
                if ((ret = fcntl(fptr->fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
                if ((ret & FD_CLOEXEC) != flag) {
                    ret = (ret & ~FD_CLOEXEC) | flag;
                    ret = fcntl(fd, F_SETFD, ret);
                    if (ret != 0) rb_sys_fail_path(fptr->pathv);
                }
            }

        }

        GetOpenFile(io, fptr);
        if (fptr && 0 <= (fd = fptr->fd)) {
            if ((ret = fcntl(fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
            if ((ret & FD_CLOEXEC) != flag) {
                ret = (ret & ~FD_CLOEXEC) | flag;
                ret = fcntl(fd, F_SETFD, ret);
                if (ret != 0) rb_sys_fail_path(fptr->pathv);
            }
        }
        return Qnil;
    }

close_on_exec? → true or false click to toggle source

Returns `true` if ios will be closed on exec.

    f = open("/dev/null")
    f.close_on_exec?                 #=> false
    f.close_on_exec = true
    f.close_on_exec?                 #=> true
    f.close_on_exec = false
    f.close_on_exec?                 #=> false

    static VALUE
    rb_io_close_on_exec_p(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;
        int fd, ret;

        write_io = GetWriteIO(io);
        if (io != write_io) {
            GetOpenFile(write_io, fptr);
            if (fptr && 0 <= (fd = fptr->fd)) {
                if ((ret = fcntl(fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
                if (!(ret & FD_CLOEXEC)) return Qfalse;
            }
        }

        GetOpenFile(io, fptr);
        if (fptr && 0 <= (fd = fptr->fd)) {
            if ((ret = fcntl(fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
            if (!(ret & FD_CLOEXEC)) return Qfalse;
        }
        return Qtrue;
    }

close_read → nil click to toggle source

Closes the read end of a duplex I/O stream (i.e., one that contains both a read and a write stream, such as a pipe). Will raise an `IOError` if the stream is not duplexed.

    f = IO.popen("/bin/sh","r+")
    f.close_read
    f.readlines

produces:

    prog.rb:3:in `readlines': not opened for reading (IOError)
     from prog.rb:3

Calling this method on closed `IO` object is just ignored since Ruby 2.3.

    static VALUE
    rb_io_close_read(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;

        fptr = rb_io_get_fptr(rb_io_taint_check(io));
        if (fptr->fd < 0) return Qnil;
        if (is_socket(fptr->fd, fptr->pathv)) {
    #ifndef SHUT_RD
    # define SHUT_RD 0
    #endif
            if (shutdown(fptr->fd, SHUT_RD) < 0)
                rb_sys_fail_path(fptr->pathv);
            fptr->mode &= ~FMODE_READABLE;
            if (!(fptr->mode & FMODE_WRITABLE))
                return rb_io_close(io);
            return Qnil;
        }

        write_io = GetWriteIO(io);
        if (io != write_io) {
            rb_io_t *wfptr;
            wfptr = rb_io_get_fptr(rb_io_taint_check(write_io));
            wfptr->pid = fptr->pid;
            fptr->pid = 0;
            RFILE(io)->fptr = wfptr;
            /* bind to write_io temporarily to get rid of memory/fd leak */
            fptr->tied_io_for_writing = 0;
            RFILE(write_io)->fptr = fptr;
            rb_io_fptr_cleanup(fptr, FALSE);
            /* should not finalize fptr because another thread may be reading it */
            return Qnil;
        }

        if ((fptr->mode & (FMODE_DUPLEX|FMODE_WRITABLE)) == FMODE_WRITABLE) {
            rb_raise(rb_eIOError, "closing non-duplex IO for reading");
        }
        return rb_io_close(io);
    }

close_write → nil click to toggle source

Closes the write end of a duplex I/O stream (i.e., one that contains both a read and a write stream, such as a pipe). Will raise an `IOError` if the stream is not duplexed.

    f = IO.popen("/bin/sh","r+")
    f.close_write
    f.print "nowhere"

produces:

    prog.rb:3:in `write': not opened for writing (IOError)
     from prog.rb:3:in `print'
     from prog.rb:3

Calling this method on closed `IO` object is just ignored since Ruby 2.3.

    static VALUE
    rb_io_close_write(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;

        write_io = GetWriteIO(io);
        fptr = rb_io_get_fptr(rb_io_taint_check(write_io));
        if (fptr->fd < 0) return Qnil;
        if (is_socket(fptr->fd, fptr->pathv)) {
    #ifndef SHUT_WR
    # define SHUT_WR 1
    #endif
            if (shutdown(fptr->fd, SHUT_WR) < 0)
                rb_sys_fail_path(fptr->pathv);
            fptr->mode &= ~FMODE_WRITABLE;
            if (!(fptr->mode & FMODE_READABLE))
                return rb_io_close(write_io);
            return Qnil;
        }

        if ((fptr->mode & (FMODE_DUPLEX|FMODE_READABLE)) == FMODE_READABLE) {
            rb_raise(rb_eIOError, "closing non-duplex IO for writing");
        }

        if (io != write_io) {
            fptr = rb_io_get_fptr(rb_io_taint_check(io));
            fptr->tied_io_for_writing = 0;
        }
        rb_io_close(write_io);
        return Qnil;
    }

closed? → true or false click to toggle source

Returns `true` if ios is completely closed (for duplex streams, both reader and writer), `false` otherwise.

    f = File.new("testfile")
    f.close         #=> nil
    f.closed?       #=> true
    f = IO.popen("/bin/sh","r+")
    f.close_write   #=> nil
    f.closed?       #=> false
    f.close_read    #=> nil
    f.closed?       #=> true

    static VALUE
    rb_io_closed(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;
        rb_io_t *write_fptr;

        write_io = GetWriteIO(io);
        if (io != write_io) {
            write_fptr = RFILE(write_io)->fptr;
            if (write_fptr && 0 <= write_fptr->fd) {
                return Qfalse;
            }
        }

        fptr = rb_io_get_fptr(io);
        return 0 <= fptr->fd ? Qfalse : Qtrue;
    }

codepoints() click to toggle source

This is a deprecated alias for `each_codepoint`.

    static VALUE
    rb_io_codepoints(VALUE io)
    {
        rb_warn("IO#codepoints is deprecated; use #each_codepoint instead");
        if (!rb_block_given_p())
            return rb_enumeratorize(io, ID2SYM(rb_intern("each_codepoint")), 0, 0);
        return rb_io_each_codepoint(io);
    }

cooked {|io| } click to toggle source

Yields `self` within cooked mode.

    STDIN.cooked(&:gets)

will read and return a line with echo back and line editing.

You must require 'io/console' to use this method.

    static VALUE
    console_cooked(VALUE io)
    {
        return ttymode(io, rb_yield, set_cookedmode, NULL);
    }

cooked! click to toggle source

Enables cooked mode.

If the terminal mode needs to be back, use io.cooked { … }.

You must require 'io/console' to use this method.

    static VALUE
    console_set_cooked(VALUE io)
    {
        conmode t;
        rb_io_t *fptr;
        int fd;

        GetOpenFile(io, fptr);
        fd = GetReadFD(fptr);
        if (!getattr(fd, &t)) rb_sys_fail(0);
        set_cookedmode(&t, NULL);
        if (!setattr(fd, &t)) rb_sys_fail(0);
        return io;
    }

cursor() click to toggle source

    static VALUE
    console_cursor_pos(VALUE io)
    {
        rb_io_t *fptr;
        int fd;
        rb_console_size_t ws;

        GetOpenFile(io, fptr);
        fd = GetWriteFD(fptr);
        if (!GetConsoleScreenBufferInfo((HANDLE)rb_w32_get_osfhandle(fd), &ws)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
        return rb_assoc_new(UINT2NUM(ws.dwCursorPosition.X), UINT2NUM(ws.dwCursorPosition.Y));
    }

cursor=(p1) click to toggle source

    static VALUE
    console_cursor_set(VALUE io, VALUE cpos)
    {
        cpos = rb_convert_type(cpos, T_ARRAY, "Array", "to_ary");
        if (RARRAY_LEN(cpos) != 2) rb_raise(rb_eArgError, "expected 2D coordinate");
        return console_goto(io, RARRAY_AREF(cpos, 0), RARRAY_AREF(cpos, 1));
    }

each(sep=$/ [, getline_args]) {|line| block } → ios click to toggle source
each(limit [, getline_args]) {|line| block } → ios
each(sep, limit [, getline_args]) {|line| block } → ios
each(...) → an_enumerator
each_line(sep=$/ [, getline_args]) {|line| block } → ios
each_line(limit [, getline_args]) {|line| block } → ios
each_line(sep, limit [, getline_args]) {|line| block } → ios
each_line(...) → an_enumerator

Executes the block for every line in ios, where lines are separated by sep. ios must be opened for reading or an `IOError` will be raised.

If no block is given, an enumerator is returned instead.

    f = File.new("testfile")
    f.each {|line| puts "#{f.lineno}: #{line}" }

produces:

    1: This is line one
    2: This is line two
    3: This is line three
    4: And so on...

See `IO.readlines` for details about getline_args.

    static VALUE
    rb_io_each_line(int argc, VALUE *argv, VALUE io)
    {
        VALUE str;
        struct getline_arg args;

        RETURN_ENUMERATOR(io, argc, argv);
        prepare_getline_args(argc, argv, &args, io);
        if (args.limit == 0)
            rb_raise(rb_eArgError, "invalid limit: 0 for each_line");
        while (!NIL_P(str = rb_io_getline_1(args.rs, args.limit, args.chomp, io))) {
            rb_yield(str);
        }
        return io;
    }

each_byte {|byte| block } → ios click to toggle source
each_byte → an_enumerator

Calls the given block once for each byte (0..255) in ios, passing the byte as an argument. The stream must be opened for reading or an `IOError` will be raised.

If no block is given, an enumerator is returned instead.

    f = File.new("testfile")
    checksum = 0
    f.each_byte {|x| checksum ^= x }   #=> #<File:testfile>
    checksum                           #=> 12

    static VALUE
    rb_io_each_byte(VALUE io)
    {
        rb_io_t *fptr;

        RETURN_ENUMERATOR(io, 0, 0);
        GetOpenFile(io, fptr);

        do {
            while (fptr->rbuf.len > 0) {
                char *p = fptr->rbuf.ptr + fptr->rbuf.off++;
                fptr->rbuf.len--;
                rb_yield(INT2FIX(*p & 0xff));
                errno = 0;
            }
            rb_io_check_byte_readable(fptr);
            READ_CHECK(fptr);
        } while (io_fillbuf(fptr) >= 0);
        return io;
    }

each_char {|c| block } → ios click to toggle source
each_char → an_enumerator

Calls the given block once for each character in ios, passing the character as an argument. The stream must be opened for reading or an `IOError` will be raised.

If no block is given, an enumerator is returned instead.

    f = File.new("testfile")
    f.each_char {|c| print c, ' ' }   #=> #<File:testfile>

    static VALUE
    rb_io_each_char(VALUE io)
    {
        rb_io_t *fptr;
        rb_encoding *enc;
        VALUE c;

        RETURN_ENUMERATOR(io, 0, 0);
        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        enc = io_input_encoding(fptr);
        READ_CHECK(fptr);
        while (!NIL_P(c = io_getc(fptr, enc))) {
            rb_yield(c);
        }
        return io;
    }

each_codepoint {|c| block } → ios click to toggle source
codepoints {|c| block } → ios
each_codepoint → an_enumerator
codepoints → an_enumerator

Passes the `Integer` ordinal of each character in ios, passing the codepoint as an argument. The stream must be opened for reading or an `IOError` will be raised.

If no block is given, an enumerator is returned instead.

    static VALUE
    rb_io_each_codepoint(VALUE io)
    {
        rb_io_t *fptr;
        rb_encoding *enc;
        unsigned int c;
        int r, n;

        RETURN_ENUMERATOR(io, 0, 0);
        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        READ_CHECK(fptr);
        if (NEED_READCONV(fptr)) {
            SET_BINARY_MODE(fptr);
            r = 1;         /* no invalid char yet */
            for (;;) {
                make_readconv(fptr, 0);
                for (;;) {
                    if (fptr->cbuf.len) {
                        if (fptr->encs.enc)
                            r = rb_enc_precise_mbclen(fptr->cbuf.ptr+fptr->cbuf.off,
                                                      fptr->cbuf.ptr+fptr->cbuf.off+fptr->cbuf.len,
                                                      fptr->encs.enc);
                        else
                            r = ONIGENC_CONSTRUCT_MBCLEN_CHARFOUND(1);
                        if (!MBCLEN_NEEDMORE_P(r))
                            break;
                        if (fptr->cbuf.len == fptr->cbuf.capa) {
                            rb_raise(rb_eIOError, "too long character");
                        }
                    }
                    if (more_char(fptr) == MORE_CHAR_FINISHED) {
                        clear_readconv(fptr);
                        if (!MBCLEN_CHARFOUND_P(r)) {
                            enc = fptr->encs.enc;
                            goto invalid;
                        }
                        return io;
                    }
                }
                if (MBCLEN_INVALID_P(r)) {
                    enc = fptr->encs.enc;
                    goto invalid;
                }
                n = MBCLEN_CHARFOUND_LEN(r);
                if (fptr->encs.enc) {
                    c = rb_enc_codepoint(fptr->cbuf.ptr+fptr->cbuf.off,
                                         fptr->cbuf.ptr+fptr->cbuf.off+fptr->cbuf.len,
                                         fptr->encs.enc);
                }
                else {
                    c = (unsigned char)fptr->cbuf.ptr[fptr->cbuf.off];
                }
                fptr->cbuf.off += n;
                fptr->cbuf.len -= n;
                rb_yield(UINT2NUM(c));
            }
        }
        NEED_NEWLINE_DECORATOR_ON_READ_CHECK(fptr);
        enc = io_input_encoding(fptr);
        while (io_fillbuf(fptr) >= 0) {
            r = rb_enc_precise_mbclen(fptr->rbuf.ptr+fptr->rbuf.off,
                                      fptr->rbuf.ptr+fptr->rbuf.off+fptr->rbuf.len, enc);
            if (MBCLEN_CHARFOUND_P(r) &&
                (n = MBCLEN_CHARFOUND_LEN(r)) <= fptr->rbuf.len) {
                c = rb_enc_codepoint(fptr->rbuf.ptr+fptr->rbuf.off,
                                     fptr->rbuf.ptr+fptr->rbuf.off+fptr->rbuf.len, enc);
                fptr->rbuf.off += n;
                fptr->rbuf.len -= n;
                rb_yield(UINT2NUM(c));
            }
            else if (MBCLEN_INVALID_P(r)) {
              invalid:
                rb_raise(rb_eArgError, "invalid byte sequence in %s", rb_enc_name(enc));
            }
            else if (MBCLEN_NEEDMORE_P(r)) {
                char cbuf[8], *p = cbuf;
                int more = MBCLEN_NEEDMORE_LEN(r);
                if (more > numberof(cbuf)) goto invalid;
                more += n = fptr->rbuf.len;
                if (more > numberof(cbuf)) goto invalid;
                while ((n = (int)read_buffered_data(p, more, fptr)) > 0 &&
                       (p += n, (more -= n) > 0)) {
                    if (io_fillbuf(fptr) < 0) goto invalid;
                    if ((n = fptr->rbuf.len) > more) n = more;
                }
                r = rb_enc_precise_mbclen(cbuf, p, enc);
                if (!MBCLEN_CHARFOUND_P(r)) goto invalid;
                c = rb_enc_codepoint(cbuf, p, enc);
                rb_yield(UINT2NUM(c));
            }
            else {
                continue;
            }
        }
        return io;
    }

each_line(sep=$/ [, getline_args]) {|line| block } → ios click to toggle source
each_line(limit [, getline_args]) {|line| block } → ios
each_line(sep, limit [, getline_args]) {|line| block } → ios
each_line(...) → an_enumerator

Executes the block for every line in ios, where lines are separated by sep. ios must be opened for reading or an `IOError` will be raised.

If no block is given, an enumerator is returned instead.

    f = File.new("testfile")
    f.each {|line| puts "#{f.lineno}: #{line}" }

produces:

    1: This is line one
    2: This is line two
    3: This is line three
    4: And so on...

See `IO.readlines` for details about getline_args.

    static VALUE
    rb_io_each_line(int argc, VALUE *argv, VALUE io)
    {
        VALUE str;
        struct getline_arg args;

        RETURN_ENUMERATOR(io, argc, argv);
        prepare_getline_args(argc, argv, &args, io);
        if (args.limit == 0)
            rb_raise(rb_eArgError, "invalid limit: 0 for each_line");
        while (!NIL_P(str = rb_io_getline_1(args.rs, args.limit, args.chomp, io))) {
            rb_yield(str);
        }
        return io;
    }

echo = flag click to toggle source

Enables/disables echo back. On some platforms, all combinations of this flags and raw/cooked mode may not be valid.

You must require 'io/console' to use this method.

    static VALUE
    console_set_echo(VALUE io, VALUE f)
    {
        conmode t;
        rb_io_t *fptr;
        int fd;

        GetOpenFile(io, fptr);
        fd = GetReadFD(fptr);
        if (!getattr(fd, &t)) rb_sys_fail(0);
        if (RTEST(f))
            set_echo(&t, NULL);
        else
            set_noecho(&t, NULL);
        if (!setattr(fd, &t)) rb_sys_fail(0);
        return io;
    }

echo? → true or false click to toggle source

Returns `true` if echo back is enabled.

You must require 'io/console' to use this method.

    static VALUE
    console_echo_p(VALUE io)
    {
        conmode t;
        rb_io_t *fptr;
        int fd;

        GetOpenFile(io, fptr);
        fd = GetReadFD(fptr);
        if (!getattr(fd, &t)) rb_sys_fail(0);
        return echo_p(&t) ? Qtrue : Qfalse;
    }

eof → true or false click to toggle source
eof? → true or false

Returns true if ios is at end of file that means there are no more data to read. The stream must be opened for reading or an `IOError` will be raised.

    f = File.new("testfile")
    dummy = f.readlines
    f.eof   #=> true

If ios is a stream such as pipe or socket, `IO#eof?` blocks until the other end sends some data or closes it.

    r, w = IO.pipe
    Thread.new { sleep 1; w.close }
    r.eof?  #=> true after 1 second blocking

    r, w = IO.pipe
    Thread.new { sleep 1; w.puts "a" }
    r.eof?  #=> false after 1 second blocking

    r, w = IO.pipe
    r.eof?  # blocks forever

Note that `IO#eof?` reads data to the input byte buffer. So `IO#sysread` may not behave as you intend with `IO#eof?`, unless you call `IO#rewind` first (which is not available for some streams).

    VALUE
    rb_io_eof(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        if (READ_CHAR_PENDING(fptr)) return Qfalse;
        if (READ_DATA_PENDING(fptr)) return Qfalse;
        READ_CHECK(fptr);
    #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
        if (!NEED_READCONV(fptr) && NEED_NEWLINE_DECORATOR_ON_READ(fptr)) {
            return eof(fptr->fd) ? Qtrue : Qfalse;
        }
    #endif
        if (io_fillbuf(fptr) < 0) {
            return Qtrue;
        }
        return Qfalse;
    }

eof? → true or false click to toggle source

Returns true if ios is at end of file that means there are no more data to read. The stream must be opened for reading or an `IOError` will be raised.

    f = File.new("testfile")
    dummy = f.readlines
    f.eof   #=> true

If ios is a stream such as pipe or socket, `IO#eof?` blocks until the other end sends some data or closes it.

    r, w = IO.pipe
    Thread.new { sleep 1; w.close }
    r.eof?  #=> true after 1 second blocking

    r, w = IO.pipe
    Thread.new { sleep 1; w.puts "a" }
    r.eof?  #=> false after 1 second blocking

    r, w = IO.pipe
    r.eof?  # blocks forever

Note that `IO#eof?` reads data to the input byte buffer. So `IO#sysread` may not behave as you intend with `IO#eof?`, unless you call `IO#rewind` first (which is not available for some streams).

    VALUE
    rb_io_eof(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        if (READ_CHAR_PENDING(fptr)) return Qfalse;
        if (READ_DATA_PENDING(fptr)) return Qfalse;
        READ_CHECK(fptr);
    #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
        if (!NEED_READCONV(fptr) && NEED_NEWLINE_DECORATOR_ON_READ(fptr)) {
            return eof(fptr->fd) ? Qtrue : Qfalse;
        }
    #endif
        if (io_fillbuf(fptr) < 0) {
            return Qtrue;
        }
        return Qfalse;
    }

IO#expect(pattern,timeout=9999999) → Array click to toggle source
IO#expect(pattern,timeout=9999999) { |result| ... } → nil

Reads from the `IO` until the given `pattern` matches or the `timeout` is over.

It returns an array with the read buffer, followed by the matches. If a block is given, the result is yielded to the block and returns nil.

When called without a block, it waits until the input that matches the given `pattern` is obtained from the `IO` or the time specified as the timeout passes. An array is returned when the pattern is obtained from the `IO`. The first element of the array is the entire string obtained from the `IO` until the pattern matches, followed by elements indicating which the pattern which matched to the anchor in the regular expression.

The optional timeout parameter defines, in seconds, the total time to wait for the pattern. If the timeout expires or eof is found, nil is returned or yielded. However, the buffer in a timeout session is kept for the next expect call. The default timeout is 9999999 seconds.

    # File ext/pty/lib/expect.rb, line 33
    def expect(pat,timeout=9999999)
      buf = ''.dup
      case pat
      when String
        e_pat = Regexp.new(Regexp.quote(pat))
      when Regexp
        e_pat = pat
      else
        raise TypeError, "unsupported pattern class: #{pat.class}"
      end
      @unusedBuf ||= ''
      while true
        if not @unusedBuf.empty?
          c = @unusedBuf.slice!(0)
        elsif !IO.select([self],nil,nil,timeout) or eof? then
          result = nil
          @unusedBuf = buf
          break
        else
          c = getc
        end
        buf << c
        if $expect_verbose
          STDOUT.print c
          STDOUT.flush
        end
        if mat=e_pat.match(buf) then
          result = [buf,*mat.captures]
          break
        end
      end
      if block_given? then
        yield result
      else
        return result
      end
      nil
    end

external_encoding → encoding click to toggle source

Returns the `Encoding` object that represents the encoding of the file. If io is in write mode and no encoding is specified, returns `nil`.

    static VALUE
    rb_io_external_encoding(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (fptr->encs.enc2) {
            return rb_enc_from_encoding(fptr->encs.enc2);
        }
        if (fptr->mode & FMODE_WRITABLE) {
            if (fptr->encs.enc)
                return rb_enc_from_encoding(fptr->encs.enc);
            return Qnil;
        }
        return rb_enc_from_encoding(io_read_encoding(fptr));
    }

fcntl(integer_cmd, arg) → integer click to toggle source

Provides a mechanism for issuing low-level commands to control or query file-oriented I/O streams. Arguments and results are platform dependent. If arg is a number, its value is passed directly. If it is a string, it is interpreted as a binary sequence of bytes (`Array#pack` might be a useful way to build this string). On Unix platforms, see `fcntl(2)` for details. Not implemented on all platforms.

    static VALUE
    rb_io_fcntl(int argc, VALUE *argv, VALUE io)
    {
        VALUE req, arg;

        rb_scan_args(argc, argv, "11", &req, &arg);
        return rb_fcntl(io, req, arg);
    }

fdatasync → 0 or nil click to toggle source

Immediately writes all buffered data in ios to disk.

If the underlying operating system does not support fdatasync(2), `IO#fsync` is called instead (which might raise a `NotImplementedError`).

    static VALUE
    rb_io_fdatasync(VALUE io)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);

        if (io_fflush(fptr) < 0)
            rb_sys_fail(0);

        if ((int)rb_thread_io_blocking_region(nogvl_fdatasync, fptr, fptr->fd) == 0)
            return INT2FIX(0);

        /* fall back */
        return rb_io_fsync(io);
    }

fileno → integer click to toggle source
to_i → integer

Returns an integer representing the numeric file descriptor for ios.

    $stdin.fileno    #=> 0
    $stdout.fileno   #=> 1

    static VALUE
    rb_io_fileno(VALUE io)
    {
        rb_io_t *fptr = RFILE(io)->fptr;
        int fd;

        rb_io_check_closed(fptr);
        fd = fptr->fd;
        return INT2FIX(fd);
    }

Also aliased as: to_i
flush → ios click to toggle source

Flushes any buffered data within ios to the underlying operating system (note that this is Ruby internal buffering only; the OS may buffer the data as well).

    $stdout.print "no newline"
    $stdout.flush

produces:

    no newline

    VALUE
    rb_io_flush(VALUE io)
    {
        return rb_io_flush_raw(io, 1);
    }

fsync → 0 or nil click to toggle source

Immediately writes all buffered data in ios to disk. Note that `fsync` differs from using `IO#sync=`. The latter ensures that data is flushed from Ruby's buffers, but does not guarantee that the underlying operating system actually writes it to disk.

`NotImplementedError` is raised if the underlying operating system does not support fsync(2).

    static VALUE
    rb_io_fsync(VALUE io)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);

        if (io_fflush(fptr) < 0)
            rb_sys_fail(0);
        if ((int)rb_thread_io_blocking_region(nogvl_fsync, fptr, fptr->fd) < 0)
            rb_sys_fail_path(fptr->pathv);
        return INT2FIX(0);
    }

getbyte → integer or nil click to toggle source

Gets the next 8-bit byte (0..255) from ios. Returns `nil` if called at end of file.

    f = File.new("testfile")
    f.getbyte   #=> 84
    f.getbyte   #=> 104

    VALUE
    rb_io_getbyte(VALUE io)
    {
        rb_io_t *fptr;
        int c;

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);
        READ_CHECK(fptr);
        if (fptr->fd == 0 && (fptr->mode & FMODE_TTY) && RB_TYPE_P(rb_stdout, T_FILE)) {
            rb_io_t *ofp;
            GetOpenFile(rb_stdout, ofp);
            if (ofp->mode & FMODE_TTY) {
                rb_io_flush(rb_stdout);
            }
        }
        if (io_fillbuf(fptr) < 0) {
            return Qnil;
        }
        fptr->rbuf.off++;
        fptr->rbuf.len--;
        c = (unsigned char)fptr->rbuf.ptr[fptr->rbuf.off-1];
        return INT2FIX(c & 0xff);
    }

getc → string or nil click to toggle source

Reads a one-character string from ios. Returns `nil` if called at end of file.

    f = File.new("testfile")
    f.getc   #=> "h"
    f.getc   #=> "e"

    static VALUE
    rb_io_getc(VALUE io)
    {
        rb_io_t *fptr;
        rb_encoding *enc;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        enc = io_input_encoding(fptr);
        READ_CHECK(fptr);
        return io_getc(fptr, enc);
    }

getch(min: nil, time: nil) → char click to toggle source

Reads and returns a character in raw mode.

See `IO#raw` for details on the parameters.

You must require 'io/console' to use this method.

    static VALUE
    console_getch(int argc, VALUE *argv, VALUE io)
    {
        rawmode_arg_t opts, *optp = rawmode_opt(argc, argv, &opts);
        return ttymode(io, getc_call, set_rawmode, optp);
    }

getpass(prompt=nil) → string click to toggle source

Reads and returns a line without echo back. Prints `prompt` unless it is `nil`.

You must require 'io/console' to use this method.

    static VALUE
    console_getpass(int argc, VALUE *argv, VALUE io)
    {
        VALUE str, wio;

        rb_check_arity(argc, 0, 1);
        wio = rb_io_get_write_io(io);
        if (wio == io && io == rb_stdin) wio = rb_stderr;
        prompt(argc, argv, wio);
        str = rb_ensure(getpass_call, io, puts_call, wio);
        return str_chomp(str);
    }

gets(sep=$/ [, getline_args]) → string or nil click to toggle source
gets(limit [, getline_args]) → string or nil
gets(sep, limit [, getline_args]) → string or nil

Reads the next “line'' from the I/O stream; lines are separated by sep. A separator of `nil` reads the entire contents, and a zero-length separator reads the input a paragraph at a time (two successive newlines in the input separate paragraphs). The stream must be opened for reading or an `IOError` will be raised. The line read in will be returned and also assigned to `$_`. Returns `nil` if called at end of file. If the first argument is an integer, or optional second argument is given, the returning string would not be longer than the given value in bytes.

    File.new("testfile").gets   #=> "This is line one\n"
    $_                          #=> "This is line one\n"

    File.new("testfile").gets(4)#=> "This"

If `IO` contains multibyte characters byte then `gets(1)` returns character entirely:

    # Russian characters take 2 bytes
    File.write("testfile", "\u{442 435 441 442}")
    File.open("testfile") {|f|f.gets(1)} #=> "\u0442"
    File.open("testfile") {|f|f.gets(2)} #=> "\u0442"
    File.open("testfile") {|f|f.gets(3)} #=> "\u0442\u0435"
    File.open("testfile") {|f|f.gets(4)} #=> "\u0442\u0435"

    static VALUE
    rb_io_gets_m(int argc, VALUE *argv, VALUE io)
    {
        VALUE str;

        str = rb_io_getline(argc, argv, io);
        rb_lastline_set(str);

        return str;
    }

goto(p1, p2) click to toggle source

    static VALUE
    console_goto(VALUE io, VALUE x, VALUE y)
    {
        rb_io_t *fptr;
        int fd;
        COORD pos;

        GetOpenFile(io, fptr);
        fd = GetWriteFD(fptr);
        pos.X = NUM2UINT(x);
        pos.Y = NUM2UINT(y);
        if (!SetConsoleCursorPosition((HANDLE)rb_w32_get_osfhandle(fd), pos)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
        return io;
    }

iflush click to toggle source

Flushes input buffer in kernel.

You must require 'io/console' to use this method.

    static VALUE
    console_iflush(VALUE io)
    {
        rb_io_t *fptr;
        int fd;

        GetOpenFile(io, fptr);
        fd = GetReadFD(fptr);
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        if (tcflush(fd, TCIFLUSH)) rb_sys_fail(0);
    #endif
        (void)fd;
        return io;
    }

inspect → string click to toggle source

Return a string describing this `IO` object.

    static VALUE
    rb_io_inspect(VALUE obj)
    {
        rb_io_t *fptr;
        VALUE result;
        static const char closed[] = " (closed)";

        fptr = RFILE(obj)->fptr;
        if (!fptr) return rb_any_to_s(obj);
        result = rb_str_new_cstr("#<");
        rb_str_append(result, rb_class_name(CLASS_OF(obj)));
        rb_str_cat2(result, ":");
        if (NIL_P(fptr->pathv)) {
            if (fptr->fd < 0) {
                rb_str_cat(result, closed+1, strlen(closed)-1);
            }
            else {
                rb_str_catf(result, "fd %d", fptr->fd);
            }
        }
        else {
            rb_str_append(result, fptr->pathv);
            if (fptr->fd < 0) {
                rb_str_cat(result, closed, strlen(closed));
            }
        }
        return rb_str_cat2(result, ">");
    }

internal_encoding → encoding click to toggle source

Returns the `Encoding` of the internal string if conversion is specified. Otherwise returns `nil`.

    static VALUE
    rb_io_internal_encoding(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (!fptr->encs.enc2) return Qnil;
        return rb_enc_from_encoding(io_read_encoding(fptr));
    }

ioctl(integer_cmd, arg) → integer click to toggle source

Provides a mechanism for issuing low-level commands to control or query I/O devices. Arguments and results are platform dependent. If arg is a number, its value is passed directly. If it is a string, it is interpreted as a binary sequence of bytes. On Unix platforms, see `ioctl(2)` for details. Not implemented on all platforms.

    static VALUE
    rb_io_ioctl(int argc, VALUE *argv, VALUE io)
    {
        VALUE req, arg;

        rb_scan_args(argc, argv, "11", &req, &arg);
        return rb_ioctl(io, req, arg);
    }

ioflush click to toggle source

Flushes input and output buffers in kernel.

You must require 'io/console' to use this method.

    static VALUE
    console_ioflush(VALUE io)
    {
        rb_io_t *fptr;
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        int fd1, fd2;
    #endif

        GetOpenFile(io, fptr);
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        fd1 = GetReadFD(fptr);
        fd2 = GetWriteFD(fptr);
        if (fd2 != -1 && fd1 != fd2) {
            if (tcflush(fd1, TCIFLUSH)) rb_sys_fail(0);
            if (tcflush(fd2, TCOFLUSH)) rb_sys_fail(0);
        }
        else {
            if (tcflush(fd1, TCIOFLUSH)) rb_sys_fail(0);
        }
    #endif
        return io;
    }

isatty → true or false click to toggle source

Returns `true` if ios is associated with a terminal device (tty), `false` otherwise.

    File.new("testfile").isatty   #=> false
    File.new("/dev/tty").isatty   #=> true

    static VALUE
    rb_io_isatty(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (isatty(fptr->fd) == 0)
            return Qfalse;
        return Qtrue;
    }

lineno → integer click to toggle source

Returns the current line number in ios. The stream must be opened for reading. `lineno` counts the number of times `gets` is called rather than the number of newlines encountered. The two values will differ if `gets` is called with a separator other than newline.

Methods that use `$/` like `each`, `lines` and `readline` will also increment `lineno`.

See also the `$.` variable.

    f = File.new("testfile")
    f.lineno   #=> 0
    f.gets     #=> "This is line one\n"
    f.lineno   #=> 1
    f.gets     #=> "This is line two\n"
    f.lineno   #=> 2

    static VALUE
    rb_io_lineno(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);
        return INT2NUM(fptr->lineno);
    }

lineno = integer → integer click to toggle source

Manually sets the current line number to the given value. `$.` is updated only on the next read.

    f = File.new("testfile")
    f.gets                     #=> "This is line one\n"
    $.                         #=> 1
    f.lineno = 1000
    f.lineno                   #=> 1000
    $.                         #=> 1         # lineno of last read
    f.gets                     #=> "This is line two\n"
    $.                         #=> 1001      # lineno of last read

    static VALUE
    rb_io_set_lineno(VALUE io, VALUE lineno)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);
        fptr->lineno = NUM2INT(lineno);
        return lineno;
    }

lines(*args) click to toggle source

This is a deprecated alias for `each_line`.

    static VALUE
    rb_io_lines(int argc, VALUE *argv, VALUE io)
    {
        rb_warn("IO#lines is deprecated; use #each_line instead");
        if (!rb_block_given_p())
            return rb_enumeratorize(io, ID2SYM(rb_intern("each_line")), argc, argv);
        return rb_io_each_line(argc, argv, io);
    }

noecho {|io| } click to toggle source

Yields `self` with disabling echo back.

    STDIN.noecho(&:gets)

will read and return a line without echo back.

You must require 'io/console' to use this method.

    static VALUE
    console_noecho(VALUE io)
    {
        return ttymode(io, rb_yield, set_noecho, NULL);
    }

nonblock {|io| } → io click to toggle source
nonblock(boolean) {|io| } → io

Yields `self` in non-blocking mode.

When `false` is given as an argument, `self` is yielded in blocking mode. The original mode is restored after the block is executed.

    static VALUE
    rb_io_nonblock_block(int argc, VALUE *argv, VALUE io)
    {
        int nb = 1;
        rb_io_t *fptr;
        int f, restore[2];

        GetOpenFile(io, fptr);
        if (argc > 0) {
            VALUE v;
            rb_scan_args(argc, argv, "01", &v);
            nb = RTEST(v);
        }
        f = io_nonblock_mode(fptr->fd);
        restore[0] = fptr->fd;
        restore[1] = f;
        if (!io_nonblock_set(fptr->fd, f, nb))
            return rb_yield(io);
        return rb_ensure(rb_yield, io, io_nonblock_restore, (VALUE)restore);
    }

nonblock = boolean → boolean click to toggle source

Enables non-blocking mode on a stream when set to `true`, and blocking mode when set to `false`.

    static VALUE
    rb_io_nonblock_set(VALUE io, VALUE nb)
    {
        rb_io_t *fptr;
        GetOpenFile(io, fptr);
        if (RTEST(nb))
            rb_io_set_nonblock(fptr);
        else
            io_nonblock_set(fptr->fd, io_nonblock_mode(fptr->fd), RTEST(nb));
        return io;
    }

nonblock? → boolean click to toggle source

Returns `true` if an `IO` object is in non-blocking mode.

    static VALUE
    rb_io_nonblock_p(VALUE io)
    {
        rb_io_t *fptr;
        GetOpenFile(io, fptr);
        if (io_nonblock_mode(fptr->fd) & O_NONBLOCK)
            return Qtrue;
        return Qfalse;
    }

nread → int click to toggle source

Returns number of bytes that can be read without blocking. Returns zero if no information available.

    static VALUE
    io_nread(VALUE io)
    {
        rb_io_t *fptr;
        int len;
        ioctl_arg n;

        GetOpenFile(io, fptr);
        rb_io_check_readable(fptr);
        len = rb_io_read_pending(fptr);
        if (len > 0) return INT2FIX(len);
        if (!FIONREAD_POSSIBLE_P(fptr->fd)) return INT2FIX(0);
        if (ioctl(fptr->fd, FIONREAD, &n)) return INT2FIX(0);
        if (n > 0) return ioctl_arg2num(n);
        return INT2FIX(0);
    }

oflush click to toggle source

Flushes output buffer in kernel.

You must require 'io/console' to use this method.

    static VALUE
    console_oflush(VALUE io)
    {
        rb_io_t *fptr;
        int fd;

        GetOpenFile(io, fptr);
        fd = GetWriteFD(fptr);
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        if (tcflush(fd, TCOFLUSH)) rb_sys_fail(0);
    #endif
        (void)fd;
        return io;
    }

pathconf(p1) click to toggle source

Returns pathname configuration variable using fpathconf().

name should be a constant under `Etc` which begins with `PC_`.

The return value is an integer or nil. nil means indefinite limit. (fpathconf() returns -1 but errno is not set.)

    require 'etc'
    IO.pipe {|r, w|
      p w.pathconf(Etc::PC_PIPE_BUF) #=> 4096
    }

    static VALUE
    io_pathconf(VALUE io, VALUE arg)
    {
        int name;
        long ret;
        rb_io_t *fptr;

        name = NUM2INT(arg);

        GetOpenFile(io, fptr);

        errno = 0;
        ret = fpathconf(fptr->fd, name);
        if (ret == -1) {
            if (errno == 0) /* no limit */
                return Qnil;
            rb_sys_fail("fpathconf");
        }
        return LONG2NUM(ret);
    }

pid → integer click to toggle source

Returns the process ID of a child process associated with ios. This will be set by `IO.popen`.

    pipe = IO.popen("-")
    if pipe
      $stderr.puts "In parent, child pid is #{pipe.pid}"
    else
      $stderr.puts "In child, pid is #{$$}"
    end

produces:

    In child, pid is 26209
    In parent, child pid is 26209

    static VALUE
    rb_io_pid(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (!fptr->pid)
            return Qnil;
        return PIDT2NUM(fptr->pid);
    }

pos → integer click to toggle source

Returns the current offset (in bytes) of ios.

    f = File.new("testfile")
    f.pos    #=> 0
    f.gets   #=> "This is line one\n"
    f.pos    #=> 17

    static VALUE
    rb_io_tell(VALUE io)
    {
        rb_io_t *fptr;
        off_t pos;

        GetOpenFile(io, fptr);
        pos = io_tell(fptr);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);
        pos -= fptr->rbuf.len;
        return OFFT2NUM(pos);
    }

pos = integer → integer click to toggle source

Seeks to the given position (in bytes) in ios. It is not guaranteed that seeking to the right position when ios is textmode.

    f = File.new("testfile")
    f.pos = 17
    f.gets   #=> "This is line two\n"

    static VALUE
    rb_io_set_pos(VALUE io, VALUE offset)
    {
        rb_io_t *fptr;
        off_t pos;

        pos = NUM2OFFT(offset);
        GetOpenFile(io, fptr);
        pos = io_seek(fptr, pos, SEEK_SET);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);

        return OFFT2NUM(pos);
    }

pread(maxlen, offset[, outbuf]) → string click to toggle source

Reads maxlen bytes from ios using the pread system call and returns them as a string without modifying the underlying descriptor offset. This is advantageous compared to combining `IO#seek` and `IO#read` in that it is atomic, allowing multiple threads/process to share the same `IO` object for reading the file at various locations. This bypasses any userspace buffering of the `IO` layer. If the optional outbuf argument is present, it must reference a `String`, which will receive the data. Raises `SystemCallError` on error, `EOFError` at end of file and `NotImplementedError` if platform does not implement the system call.

    File.write("testfile", "This is line one\nThis is line two\n")
    File.open("testfile") do |f|
      p f.read           # => "This is line one\nThis is line two\n"
      p f.pread(12, 0)   # => "This is line"
      p f.pread(9, 8)    # => "line one\n"
    end

    static VALUE
    rb_io_pread(int argc, VALUE *argv, VALUE io)
    {
        VALUE len, offset, str;
        rb_io_t *fptr;
        ssize_t n;
        struct prdwr_internal_arg arg;
        int shrinkable;

        rb_scan_args(argc, argv, "21", &len, &offset, &str);
        arg.count = NUM2SIZET(len);
        arg.offset = NUM2OFFT(offset);

        shrinkable = io_setstrbuf(&str, (long)arg.count);
        if (arg.count == 0) return str;
        arg.buf = RSTRING_PTR(str);

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);

        arg.fd = fptr->fd;
        rb_io_check_closed(fptr);

        rb_str_locktmp(str);
        n = (ssize_t)rb_ensure(pread_internal_call, (VALUE)&arg, rb_str_unlocktmp, str);

        if (n < 0) {
            rb_sys_fail_path(fptr->pathv);
        }
        io_set_read_length(str, n, shrinkable);
        if (n == 0 && arg.count > 0) {
            rb_eof_error();
        }
        OBJ_TAINT(str);

        return str;
    }

pressed?(p1) click to toggle source

    static VALUE
    console_key_pressed_p(VALUE io, VALUE k)
    {
        int vk = -1;

        if (FIXNUM_P(k)) {
            vk = NUM2UINT(k);
        }
        else {
            const struct vktable *t;
            const char *kn;
            if (SYMBOL_P(k)) {
                k = rb_sym2str(k);
                kn = RSTRING_PTR(k);
            }
            else {
                kn = StringValuePtr(k);
            }
            t = console_win32_vk(kn, RSTRING_LEN(k));
            if (!t || (vk = (short)t->vk) == -1) {
                rb_raise(rb_eArgError, "unknown virtual key code: % "PRIsVALUE, k);
            }
        }
        return GetKeyState(vk) & 0x80 ? Qtrue : Qfalse;
    }

print → nil click to toggle source
print(obj, ...) → nil

Writes the given object(s) to ios. Returns `nil`.

The stream must be opened for writing. Each given object that isn't a string will be converted by calling its `to_s` method. When called without arguments, prints the contents of `$_`.

If the output field separator (`$,`) is not `nil`, it is inserted between objects. If the output record separator (`$\`) is not `nil`, it is appended to the output.

    $stdout.print("This is ", 100, " percent.\n")

produces:

    This is 100 percent.

    VALUE
    rb_io_print(int argc, const VALUE *argv, VALUE out)
    {
        int i;
        VALUE line;

        /* if no argument given, print `$_' */
        if (argc == 0) {
            argc = 1;
            line = rb_lastline_get();
            argv = &line;
        }
        for (i=0; i<argc; i++) {
            if (!NIL_P(rb_output_fs) && i>0) {
                rb_io_write(out, rb_output_fs);
            }
            rb_io_write(out, argv[i]);
        }
        if (argc > 0 && !NIL_P(rb_output_rs)) {
            rb_io_write(out, rb_output_rs);
        }

        return Qnil;
    }

printf(format_string [, obj, ...]) → nil click to toggle source

Formats and writes to ios, converting parameters under control of the format string. See `Kernel#sprintf` for details.

    VALUE
    rb_io_printf(int argc, const VALUE *argv, VALUE out)
    {
        rb_io_write(out, rb_f_sprintf(argc, argv));
        return Qnil;
    }

putc(obj) → obj click to toggle source

If obj is `Numeric`, write the character whose code is the least-significant byte of obj. If obj is `String`, write the first character of obj to ios. Otherwise, raise `TypeError`.

    $stdout.putc "A"
    $stdout.putc 65

produces:

    AA

    static VALUE
    rb_io_putc(VALUE io, VALUE ch)
    {
        VALUE str;
        if (RB_TYPE_P(ch, T_STRING)) {
            str = rb_str_substr(ch, 0, 1);
        }
        else {
            char c = NUM2CHR(ch);
            str = rb_str_new(&c, 1);
        }
        rb_io_write(io, str);
        return ch;
    }

puts(obj, ...) → nil click to toggle source

Writes the given object(s) to ios. Writes a newline after any that do not already end with a newline sequence. Returns `nil`.

The stream must be opened for writing. If called with an array argument, writes each element on a new line. Each given object that isn't a string or array will be converted by calling its `to_s` method. If called without arguments, outputs a single newline.

    $stdout.puts("this", "is", ["a", "test"])

produces:

    this
    is
    a
    test

Note that `puts` always uses newlines and is not affected by the output record separator (`$\`).

    VALUE
    rb_io_puts(int argc, const VALUE *argv, VALUE out)
    {
        int i, n;
        VALUE line, args[2];

        /* if no argument given, print newline. */
        if (argc == 0) {
            rb_io_write(out, rb_default_rs);
            return Qnil;
        }
        for (i=0; i<argc; i++) {
            if (RB_TYPE_P(argv[i], T_STRING)) {
                line = argv[i];
                goto string;
            }
            if (rb_exec_recursive(io_puts_ary, argv[i], out)) {
                continue;
            }
            line = rb_obj_as_string(argv[i]);
          string:
            n = 0;
            args[n++] = line;
            if (RSTRING_LEN(line) == 0 ||
                !rb_str_end_with_asciichar(line, '\n')) {
                args[n++] = rb_default_rs;
            }
            rb_io_writev(out, n, args);
        }

        return Qnil;
    }

pwrite(string, offset) → integer click to toggle source

Writes the given string to ios at offset using pwrite() system call. This is advantageous to combining `IO#seek` and `IO#write` in that it is atomic, allowing multiple threads/process to share the same `IO` object for reading the file at various locations. This bypasses any userspace buffering of the `IO` layer. Returns the number of bytes written. Raises `SystemCallError` on error and `NotImplementedError` if platform does not implement the system call.

    File.open("out", "w") do |f|
      f.pwrite("ABCDEF", 3)   #=> 6
    end

    File.read("out")          #=> "\u0000\u0000\u0000ABCDEF"

    static VALUE
    rb_io_pwrite(VALUE io, VALUE str, VALUE offset)
    {
        rb_io_t *fptr;
        ssize_t n;
        struct prdwr_internal_arg arg;
        VALUE tmp;

        if (!RB_TYPE_P(str, T_STRING))
            str = rb_obj_as_string(str);

        arg.offset = NUM2OFFT(offset);

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        rb_io_check_writable(fptr);
        arg.fd = fptr->fd;

        tmp = rb_str_tmp_frozen_acquire(str);
        arg.buf = RSTRING_PTR(tmp);
        arg.count = (size_t)RSTRING_LEN(tmp);

        n = (ssize_t)rb_thread_io_blocking_region(internal_pwrite_func, &arg, fptr->fd);
        if (n < 0) rb_sys_fail_path(fptr->pathv);
        rb_str_tmp_frozen_release(str, tmp);

        return SSIZET2NUM(n);
    }

raw(min: nil, time: nil) {|io| } click to toggle source

Yields `self` within raw mode.

    STDIN.raw(&:gets)

will read and return a line without echo back and line editing.

The parameter `min` specifies the minimum number of bytes that should be received when a read operation is performed. (default: 1)

The parameter `time` specifies the timeout in seconds with a precision of 1/10 of a second. (default: 0)

Refer to the manual page of termios for further details.

You must require 'io/console' to use this method.

    static VALUE
    console_raw(int argc, VALUE *argv, VALUE io)
    {
        rawmode_arg_t opts, *optp = rawmode_opt(argc, argv, &opts);
        return ttymode(io, rb_yield, set_rawmode, optp);
    }

raw!(min: nil, time: nil) click to toggle source

Enables raw mode.

If the terminal mode needs to be back, use io.raw { … }.

See `IO#raw` for details on the parameters.

You must require 'io/console' to use this method.

    static VALUE
    console_set_raw(int argc, VALUE *argv, VALUE io)
    {
        conmode t;
        rb_io_t *fptr;
        int fd;
        rawmode_arg_t opts, *optp = rawmode_opt(argc, argv, &opts);

        GetOpenFile(io, fptr);
        fd = GetReadFD(fptr);
        if (!getattr(fd, &t)) rb_sys_fail(0);
        set_rawmode(&t, optp);
        if (!setattr(fd, &t)) rb_sys_fail(0);
        return io;
    }

read([length [, outbuf]]) → string, outbuf, or nil click to toggle source

Reads length bytes from the I/O stream.

length must be a non-negative integer or `nil`.

If length is a positive integer, `read` tries to read length bytes without any conversion (binary mode). It returns `nil` if an EOF is encountered before anything can be read. Fewer than length bytes are returned if an EOF is encountered during the read. In the case of an integer length, the resulting string is always in ASCII-8BIT encoding.

If length is omitted or is `nil`, it reads until EOF and the encoding conversion is applied, if applicable. A string is returned even if EOF is encountered before any data is read.

If length is zero, it returns an empty string (`""`).

If the optional outbuf argument is present, it must reference a `String`, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.

When this method is called at end of file, it returns `nil` or `""`, depending on length: `read`, `read(nil)`, and `read(0)` return `""`, `read(positive_integer)` returns `nil`.

    f = File.new("testfile")
    f.read(16)   #=> "This is line one"

    # read whole file
    open("file") do |f|
      data = f.read   # This returns a string even if the file is empty.
      # ...
    end

    # iterate over fixed length records
    open("fixed-record-file") do |f|
      while record = f.read(256)
        # ...
      end
    end

    # iterate over variable length records,
    # each record is prefixed by its 32-bit length
    open("variable-record-file") do |f|
      while len = f.read(4)
        len = len.unpack("N")[0]   # 32-bit length
        record = f.read(len)       # This returns a string even if len is 0.
      end
    end

Note that this method behaves like the fread() function in C. This means it retries to invoke read(2) system calls to read data with the specified length (or until EOF). This behavior is preserved even if ios is in non-blocking mode. (This method is non-blocking flag insensitive as other methods.) If you need the behavior like a single read(2) system call, consider `readpartial`, `read_nonblock`, and `sysread`.

    static VALUE
    io_read(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        long n, len;
        VALUE length, str;
        int shrinkable;
    #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
        int previous_mode;
    #endif

        rb_scan_args(argc, argv, "02", &length, &str);

        if (NIL_P(length)) {
            GetOpenFile(io, fptr);
            rb_io_check_char_readable(fptr);
            return read_all(fptr, remain_size(fptr), str);
        }
        len = NUM2LONG(length);
        if (len < 0) {
            rb_raise(rb_eArgError, "negative length %ld given", len);
        }

        shrinkable = io_setstrbuf(&str,len);

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);
        if (len == 0) {
            io_set_read_length(str, 0, shrinkable);
            return str;
        }

        READ_CHECK(fptr);
    #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
        previous_mode = set_binary_mode_with_seek_cur(fptr);
    #endif
        n = io_fread(str, 0, len, fptr);
        io_set_read_length(str, n, shrinkable);
    #if defined(RUBY_TEST_CRLF_ENVIRONMENT) || defined(_WIN32)
        if (previous_mode == O_TEXT) {
            setmode(fptr->fd, O_TEXT);
        }
    #endif
        if (n == 0) return Qnil;
        OBJ_TAINT(str);

        return str;
    }

read_nonblock(maxlen [, options]) → string click to toggle source
read_nonblock(maxlen, outbuf [, options]) → outbuf

Reads at most maxlen bytes from ios using the read(2) system call after O_NONBLOCK is set for the underlying file descriptor.

If the optional outbuf argument is present, it must reference a `String`, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.

`read_nonblock` just calls the read(2) system call. It causes all errors the read(2) system call causes: Errno::EWOULDBLOCK, Errno::EINTR, etc. The caller should care such errors.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by `IO::WaitReadable`. So `IO::WaitReadable` can be used to rescue the exceptions for retrying read_nonblock.

`read_nonblock` causes `EOFError` on EOF.

If the read byte buffer is not empty, `read_nonblock` reads from the buffer like readpartial. In this case, the read(2) system call is not called.

When `read_nonblock` raises an exception kind of `IO::WaitReadable`, `read_nonblock` should not be called until io is readable for avoiding busy loop. This can be done as follows.

    # emulates blocking read (readpartial).
    begin
      result = io.read_nonblock(maxlen)
    rescue IO::WaitReadable
      IO.select([io])
      retry
    end

Although `IO#read_nonblock` doesn't raise `IO::WaitWritable`. `OpenSSL::Buffering#read_nonblock` can raise `IO::WaitWritable`. If `IO` and SSL should be used polymorphically, `IO::WaitWritable` should be rescued too. See the document of `OpenSSL::Buffering#read_nonblock` for sample code.

Note that this method is identical to readpartial except the non-blocking flag is set.

By specifying a keyword argument exception to `false`, you can indicate that `read_nonblock` should not raise an `IO::WaitReadable` exception, but return the symbol `:wait_readable` instead. At EOF, it will return nil instead of raising `EOFError`.

    # File prelude.rb, line 72
    def read_nonblock(len, buf = nil, exception: true)
      __read_nonblock(len, buf, exception)
    end

readbyte → integer click to toggle source

Reads a byte as with `IO#getbyte`, but raises an `EOFError` on end of file.

    static VALUE
    rb_io_readbyte(VALUE io)
    {
        VALUE c = rb_io_getbyte(io);

        if (NIL_P(c)) {
            rb_eof_error();
        }
        return c;
    }

readchar → string click to toggle source

Reads a one-character string from ios. Raises an `EOFError` on end of file.

    f = File.new("testfile")
    f.readchar   #=> "h"
    f.readchar   #=> "e"

    static VALUE
    rb_io_readchar(VALUE io)
    {
        VALUE c = rb_io_getc(io);

        if (NIL_P(c)) {
            rb_eof_error();
        }
        return c;
    }

readline(sep=$/ [, getline_args]) → string click to toggle source
readline(limit [, getline_args]) → string
readline(sep, limit [, getline_args]) → string

Reads a line as with `IO#gets`, but raises an `EOFError` on end of file.

    static VALUE
    rb_io_readline(int argc, VALUE *argv, VALUE io)
    {
        VALUE line = rb_io_gets_m(argc, argv, io);

        if (NIL_P(line)) {
            rb_eof_error();
        }
        return line;
    }

readlines(sep=$/ [, getline_args]) → array click to toggle source
readlines(limit [, getline_args]) → array
readlines(sep, limit [, getline_args]) → array

Reads all of the lines in ios, and returns them in an array. Lines are separated by the optional sep. If sep is `nil`, the rest of the stream is returned as a single record. If the first argument is an integer, or an optional second argument is given, the returning string would not be longer than the given value in bytes. The stream must be opened for reading or an `IOError` will be raised.

    f = File.new("testfile")
    f.readlines[0]   #=> "This is line one\n"

    f = File.new("testfile", chomp: true)
    f.readlines[0]   #=> "This is line one"

See `IO.readlines` for details about getline_args.

    static VALUE
    rb_io_readlines(int argc, VALUE *argv, VALUE io)
    {
        struct getline_arg args;

        prepare_getline_args(argc, argv, &args, io);
        return io_readlines(&args, io);
    }

readpartial(maxlen) → string click to toggle source
readpartial(maxlen, outbuf) → outbuf

Reads at most maxlen bytes from the I/O stream. It blocks only if ios has no data immediately available. It doesn't block if some data available.

If the optional outbuf argument is present, it must reference a `String`, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.

It raises `EOFError` on end of file.

readpartial is designed for streams such as pipe, socket, tty, etc. It blocks only when no data immediately available. This means that it blocks only when following all conditions hold.

- the byte buffer in the `IO` object is empty.

- the content of the stream is empty.

- the stream is not reached to EOF.

When readpartial blocks, it waits data or EOF on the stream. If some data is reached, readpartial returns with the data. If EOF is reached, readpartial raises `EOFError`.

When readpartial doesn't blocks, it returns or raises immediately. If the byte buffer is not empty, it returns the data in the buffer. Otherwise if the stream has some content, it returns the data in the stream. Otherwise if the stream is reached to EOF, it raises `EOFError`.

    r, w = IO.pipe           #               buffer          pipe content
    w << "abc"               #               ""              "abc".
    r.readpartial(4096)      #=> "abc"       ""              ""
    r.readpartial(4096)      # blocks because buffer and pipe is empty.

    r, w = IO.pipe           #               buffer          pipe content
    w << "abc"               #               ""              "abc"
    w.close                  #               ""              "abc" EOF
    r.readpartial(4096)      #=> "abc"       ""              EOF
    r.readpartial(4096)      # raises EOFError

    r, w = IO.pipe           #               buffer          pipe content
    w << "abc\ndef\n"        #               ""              "abc\ndef\n"
    r.gets                   #=> "abc\n"     "def\n"         ""
    w << "ghi\n"             #               "def\n"         "ghi\n"
    r.readpartial(4096)      #=> "def\n"     ""              "ghi\n"
    r.readpartial(4096)      #=> "ghi\n"     ""              ""

Note that readpartial behaves similar to sysread. The differences are:

- If the byte buffer is not empty, read from the byte buffer instead of “sysread for buffered `IO` (IOError)”.

- It doesn't cause Errno::EWOULDBLOCK and Errno::EINTR. When readpartial meets EWOULDBLOCK and EINTR by read system call, readpartial retry the system call.

The latter means that readpartial is nonblocking-flag insensitive. It blocks on the situation `IO#sysread` causes Errno::EWOULDBLOCK as if the fd is blocking mode.

    static VALUE
    io_readpartial(int argc, VALUE *argv, VALUE io)
    {
        VALUE ret;

        ret = io_getpartial(argc, argv, io, Qnil, 0);
        if (NIL_P(ret))
            rb_eof_error();
        return ret;
    }

ready? → true, false or nil click to toggle source

Returns true if input available without blocking, or false. Returns nil if no information available.

    static VALUE
    io_ready_p(VALUE io)
    {
        rb_io_t *fptr;
        struct timeval tv = {0, 0};

        GetOpenFile(io, fptr);
        rb_io_check_readable(fptr);
        if (rb_io_read_pending(fptr)) return Qtrue;
        if (wait_for_single_fd(fptr, RB_WAITFD_IN, &tv))
            return Qtrue;
        return Qfalse;
    }

reopen(other_IO) → ios click to toggle source
reopen(path, mode [, opt]) → ios

Reassociates ios with the I/O stream given in other_IO or to a new stream opened on path. This may dynamically change the actual class of this stream. The `mode` and `opt` parameters accept the same values as `IO.open`.

    f1 = File.new("testfile")
    f2 = File.new("testfile")
    f2.readlines[0]   #=> "This is line one\n"
    f2.reopen(f1)     #=> #<File:testfile>
    f2.readlines[0]   #=> "This is line one\n"

    static VALUE
    rb_io_reopen(int argc, VALUE *argv, VALUE file)
    {
        VALUE fname, nmode, opt;
        int oflags;
        rb_io_t *fptr;

        if (rb_scan_args(argc, argv, "11:", &fname, &nmode, &opt) == 1) {
            VALUE tmp = rb_io_check_io(fname);
            if (!NIL_P(tmp)) {
                return io_reopen(file, tmp);
            }
        }

        FilePathValue(fname);
        rb_io_taint_check(file);
        fptr = RFILE(file)->fptr;
        if (!fptr) {
            fptr = RFILE(file)->fptr = ZALLOC(rb_io_t);
        }

        if (!NIL_P(nmode) || !NIL_P(opt)) {
            int fmode;
            convconfig_t convconfig;

            rb_io_extract_modeenc(&nmode, 0, opt, &oflags, &fmode, &convconfig);
            if (IS_PREP_STDIO(fptr) &&
                ((fptr->mode & FMODE_READWRITE) & (fmode & FMODE_READWRITE)) !=
                (fptr->mode & FMODE_READWRITE)) {
                rb_raise(rb_eArgError,
                         "%s can't change access mode from \"%s\" to \"%s\"",
                         PREP_STDIO_NAME(fptr), rb_io_fmode_modestr(fptr->mode),
                         rb_io_fmode_modestr(fmode));
            }
            fptr->mode = fmode;
            fptr->encs = convconfig;
        }
        else {
            oflags = rb_io_fmode_oflags(fptr->mode);
        }

        fptr->pathv = fname;
        if (fptr->fd < 0) {
            fptr->fd = rb_sysopen(fptr->pathv, oflags, 0666);
            fptr->stdio_file = 0;
            return file;
        }

        if (fptr->mode & FMODE_WRITABLE) {
            if (io_fflush(fptr) < 0)
                rb_sys_fail(0);
        }
        fptr->rbuf.off = fptr->rbuf.len = 0;

        if (fptr->stdio_file) {
            int e = rb_freopen(rb_str_encode_ospath(fptr->pathv),
                               rb_io_oflags_modestr(oflags),
                               fptr->stdio_file);
            if (e) rb_syserr_fail_path(e, fptr->pathv);
            fptr->fd = fileno(fptr->stdio_file);
            rb_fd_fix_cloexec(fptr->fd);
    #ifdef USE_SETVBUF
            if (setvbuf(fptr->stdio_file, NULL, _IOFBF, 0) != 0)
                rb_warn("setvbuf() can't be honoured for %"PRIsVALUE, fptr->pathv);
    #endif
            if (fptr->stdio_file == stderr) {
                if (setvbuf(fptr->stdio_file, NULL, _IONBF, BUFSIZ) != 0)
                    rb_warn("setvbuf() can't be honoured for %"PRIsVALUE, fptr->pathv);
            }
            else if (fptr->stdio_file == stdout && isatty(fptr->fd)) {
                if (setvbuf(fptr->stdio_file, NULL, _IOLBF, BUFSIZ) != 0)
                    rb_warn("setvbuf() can't be honoured for %"PRIsVALUE, fptr->pathv);
            }
        }
        else {
            int tmpfd = rb_sysopen(fptr->pathv, oflags, 0666);
            int err = 0;
            if (rb_cloexec_dup2(tmpfd, fptr->fd) < 0)
                err = errno;
            (void)close(tmpfd);
            if (err) {
                rb_syserr_fail_path(err, fptr->pathv);
            }
        }

        return file;
    }

rewind → 0 click to toggle source

Positions ios to the beginning of input, resetting `lineno` to zero.

    f = File.new("testfile")
    f.readline   #=> "This is line one\n"
    f.rewind     #=> 0
    f.lineno     #=> 0
    f.readline   #=> "This is line one\n"

Note that it cannot be used with streams such as pipes, ttys, and sockets.

    static VALUE
    rb_io_rewind(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (io_seek(fptr, 0L, 0) < 0 && errno) rb_sys_fail_path(fptr->pathv);
        if (io == ARGF.current_file) {
            ARGF.lineno -= fptr->lineno;
        }
        fptr->lineno = 0;
        if (fptr->readconv) {
            clear_readconv(fptr);
        }

        return INT2FIX(0);
    }

scanf(str) { |current_match| ... } click to toggle source

Scans the current string until the match is exhausted, yielding each match as it is encountered in the string. A block is not necessary though, as the results will simply be aggregated into the final array.

    "123 456".block_scanf("%d")
    # => [123, 456]

If a block is given, the value from that is returned from the yield is added to an output array.

    "123 456".block_scanf("%d") do |digit,| # the ',' unpacks the Array
      digit + 100
    end
    # => [223, 556]

See `Scanf` for details on creating a format string.

You will need to require 'scanf' to use `IO#scanf`.

    # File lib/scanf.rb, line 614
    def scanf(str,&b) #:yield: current_match
      return block_scanf(str,&b) if b
      return [] unless str.size > 0

      start_position = pos rescue 0
      matched_so_far = 0
      source_buffer = ""
      result_buffer = []
      final_result = []

      fstr = Scanf::FormatString.new(str)

      loop do
        if eof || (tty? &&! fstr.match(source_buffer))
          final_result.concat(result_buffer)
          break
        end

        source_buffer << gets

        current_match = fstr.match(source_buffer)

        spec = fstr.last_spec_tried

        if spec.matched
          if spec.mid_match?
            result_buffer.replace(current_match)
            next
          end

        elsif (fstr.matched_count == fstr.spec_count - 1)
          if /\A\s*\z/.match(fstr.string_left)
            break if spec.count_space?
            result_buffer.replace(current_match)
            next
          end
        end

        final_result.concat(current_match)

        matched_so_far += source_buffer.size
        source_buffer.replace(fstr.string_left)
        matched_so_far -= source_buffer.size
        break if fstr.last_spec
        fstr.prune
      end

      begin
        seek(start_position + matched_so_far, IO::SEEK_SET)
      rescue Errno::ESPIPE
      end

      soak_up_spaces if fstr.last_spec && fstr.space

      return final_result
    end

seek(amount, whence=IO::SEEK_SET) → 0 click to toggle source

Seeks to a given offset anInteger in the stream according to the value of whence:

    :CUR or IO::SEEK_CUR  | Seeks to _amount_ plus current position
    ----------------------+--------------------------------------------------
    :END or IO::SEEK_END  | Seeks to _amount_ plus end of stream (you
                          | probably want a negative value for _amount_)
    ----------------------+--------------------------------------------------
    :SET or IO::SEEK_SET  | Seeks to the absolute location given by _amount_

Example:

    f = File.new("testfile")
    f.seek(-13, IO::SEEK_END)   #=> 0
    f.readline                  #=> "And so on...\n"

    static VALUE
    rb_io_seek_m(int argc, VALUE *argv, VALUE io)
    {
        VALUE offset, ptrname;
        int whence = SEEK_SET;

        if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
            whence = interpret_seek_whence(ptrname);
        }

        return rb_io_seek(io, offset, whence);
    }

set_encoding(ext_enc) → io click to toggle source
set_encoding("ext_enc:int_enc") → io
set_encoding(ext_enc, int_enc) → io
set_encoding("ext_enc:int_enc", opt) → io
set_encoding(ext_enc, int_enc, opt) → io

If single argument is specified, read string from io is tagged with the encoding specified. If encoding is a colon separated two encoding names “A:B”, the read string is converted from encoding A (external encoding) to encoding B (internal encoding), then tagged with B. If two arguments are specified, those must be encoding objects or encoding names, and the first one is the external encoding, and the second one is the internal encoding. If the external encoding and the internal encoding is specified, optional hash argument specify the conversion option.

    static VALUE
    rb_io_set_encoding(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        VALUE v1, v2, opt;

        if (!RB_TYPE_P(io, T_FILE)) {
            return rb_funcallv(io, id_set_encoding, argc, argv);
        }

        argc = rb_scan_args(argc, argv, "11:", &v1, &v2, &opt);
        GetOpenFile(io, fptr);
        io_encoding_set(fptr, v1, v2, opt);
        return io;
    }

stat → stat click to toggle source

Returns status information for ios as an object of type `File::Stat`.

    f = File.new("testfile")
    s = f.stat
    "%o" % s.mode   #=> "100644"
    s.blksize       #=> 4096
    s.atime         #=> Wed Apr 09 08:53:54 CDT 2003

    static VALUE
    rb_io_stat(VALUE obj)
    {
        rb_io_t *fptr;
        struct stat st;

        GetOpenFile(obj, fptr);
        if (fstat(fptr->fd, &st) == -1) {
            rb_sys_fail_path(fptr->pathv);
        }
        return rb_stat_new(&st);
    }

sync → true or false click to toggle source

Returns the current “sync mode'' of ios. When sync mode is true, all output is immediately flushed to the underlying operating system and is not buffered by Ruby internally. See also `IO#fsync`.

    f = File.new("testfile")
    f.sync   #=> false

    static VALUE
    rb_io_sync(VALUE io)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        return (fptr->mode & FMODE_SYNC) ? Qtrue : Qfalse;
    }

sync = boolean → boolean click to toggle source

Sets the “sync mode'' to `true` or `false`. When sync mode is true, all output is immediately flushed to the underlying operating system and is not buffered internally. Returns the new state. See also `IO#fsync`.

    f = File.new("testfile")
    f.sync = true

    static VALUE
    rb_io_set_sync(VALUE io, VALUE sync)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        if (RTEST(sync)) {
            fptr->mode |= FMODE_SYNC;
        }
        else {
            fptr->mode &= ~FMODE_SYNC;
        }
        return sync;
    }

sysread(maxlen[, outbuf]) → string click to toggle source

Reads maxlen bytes from ios using a low-level read and returns them as a string. Do not mix with other methods that read from ios or you may get unpredictable results.

If the optional outbuf argument is present, it must reference a `String`, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.

Raises `SystemCallError` on error and `EOFError` at end of file.

    f = File.new("testfile")
    f.sysread(16)   #=> "This is line one"

    static VALUE
    rb_io_sysread(int argc, VALUE *argv, VALUE io)
    {
        VALUE len, str;
        rb_io_t *fptr;
        long n, ilen;
        struct io_internal_read_struct iis;
        int shrinkable;

        rb_scan_args(argc, argv, "11", &len, &str);
        ilen = NUM2LONG(len);

        shrinkable = io_setstrbuf(&str, ilen);
        if (ilen == 0) return str;

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);

        if (READ_DATA_BUFFERED(fptr)) {
            rb_raise(rb_eIOError, "sysread for buffered IO");
        }

        /*
         * FIXME: removing rb_thread_wait_fd() here changes sysread semantics
         * on non-blocking IOs.  However, it's still currently possible
         * for sysread to raise Errno::EAGAIN if another thread read()s
         * the IO after we return from rb_thread_wait_fd() but before
         * we call read()
         */
        rb_thread_wait_fd(fptr->fd);

        rb_io_check_closed(fptr);

        io_setstrbuf(&str, ilen);
        iis.fd = fptr->fd;
        iis.nonblock = 1; /* for historical reasons, maybe (see above) */
        iis.buf = RSTRING_PTR(str);
        iis.capa = ilen;
        n = read_internal_locktmp(str, &iis);

        if (n < 0) {
            rb_sys_fail_path(fptr->pathv);
        }
        io_set_read_length(str, n, shrinkable);
        if (n == 0 && ilen > 0) {
            rb_eof_error();
        }
        OBJ_TAINT(str);

        return str;
    }

sysseek(offset, whence=IO::SEEK_SET) → integer click to toggle source

Seeks to a given offset in the stream according to the value of whence (see `IO#seek` for values of whence). Returns the new offset into the file.

    f = File.new("testfile")
    f.sysseek(-13, IO::SEEK_END)   #=> 53
    f.sysread(10)                  #=> "And so on."

    static VALUE
    rb_io_sysseek(int argc, VALUE *argv, VALUE io)
    {
        VALUE offset, ptrname;
        int whence = SEEK_SET;
        rb_io_t *fptr;
        off_t pos;

        if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
            whence = interpret_seek_whence(ptrname);
        }
        pos = NUM2OFFT(offset);
        GetOpenFile(io, fptr);
        if ((fptr->mode & FMODE_READABLE) &&
            (READ_DATA_BUFFERED(fptr) || READ_CHAR_PENDING(fptr))) {
            rb_raise(rb_eIOError, "sysseek for buffered IO");
        }
        if ((fptr->mode & FMODE_WRITABLE) && fptr->wbuf.len) {
            rb_warn("sysseek for buffered IO");
        }
        errno = 0;
        pos = lseek(fptr->fd, pos, whence);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);

        return OFFT2NUM(pos);
    }

syswrite(string) → integer click to toggle source

Writes the given string to ios using a low-level write. Returns the number of bytes written. Do not mix with other methods that write to ios or you may get unpredictable results. Raises `SystemCallError` on error.

    f = File.new("out", "w")
    f.syswrite("ABCDEF")   #=> 6

    static VALUE
    rb_io_syswrite(VALUE io, VALUE str)
    {
        VALUE tmp;
        rb_io_t *fptr;
        long n, len;
        const char *ptr;

        if (!RB_TYPE_P(str, T_STRING))
            str = rb_obj_as_string(str);

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        rb_io_check_writable(fptr);

        if (fptr->wbuf.len) {
            rb_warn("syswrite for buffered IO");
        }

        tmp = rb_str_tmp_frozen_acquire(str);
        RSTRING_GETMEM(tmp, ptr, len);
        n = rb_write_internal(fptr->fd, ptr, len);
        if (n < 0) rb_sys_fail_path(fptr->pathv);
        rb_str_tmp_frozen_release(str, tmp);

        return LONG2FIX(n);
    }

tell → integer click to toggle source

Returns the current offset (in bytes) of ios.

    f = File.new("testfile")
    f.pos    #=> 0
    f.gets   #=> "This is line one\n"
    f.pos    #=> 17

    static VALUE
    rb_io_tell(VALUE io)
    {
        rb_io_t *fptr;
        off_t pos;

        GetOpenFile(io, fptr);
        pos = io_tell(fptr);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);
        pos -= fptr->rbuf.len;
        return OFFT2NUM(pos);
    }

to_i()
Alias for: fileno
to_io → ios click to toggle source

Returns ios.

    static VALUE
    rb_io_to_io(VALUE io)
    {
        return io;
    }

tty? → true or false click to toggle source

Returns `true` if ios is associated with a terminal device (tty), `false` otherwise.

    File.new("testfile").isatty   #=> false
    File.new("/dev/tty").isatty   #=> true

    static VALUE
    rb_io_isatty(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (isatty(fptr->fd) == 0)
            return Qfalse;
        return Qtrue;
    }

ungetbyte(string) → nil click to toggle source
ungetbyte(integer) → nil

Pushes back bytes (passed as a parameter) onto ios, such that a subsequent buffered read will return it. Only one byte may be pushed back before a subsequent read operation (that is, you will be able to read only the last of several bytes that have been pushed back). Has no effect with unbuffered reads (such as `IO#sysread`).

    f = File.new("testfile")   #=> #<File:testfile>
    b = f.getbyte              #=> 0x38
    f.ungetbyte(b)             #=> nil
    f.getbyte                  #=> 0x38

    VALUE
    rb_io_ungetbyte(VALUE io, VALUE b)
    {
        rb_io_t *fptr;
        VALUE v;
        unsigned char c;

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);
        switch (TYPE(b)) {
          case T_NIL:
            return Qnil;
          case T_FIXNUM:
          case T_BIGNUM: ;
            v = rb_int_modulo(b, INT2FIX(256));
            c = NUM2INT(v) & 0xFF;
            b = rb_str_new((const char *)&c, 1);
            break;
          default:
            SafeStringValue(b);
        }
        io_ungetbyte(b, fptr);
        return Qnil;
    }

ungetc(string) → nil click to toggle source

Pushes back one character (passed as a parameter) onto ios, such that a subsequent buffered character read will return it. Only one character may be pushed back before a subsequent read operation (that is, you will be able to read only the last of several characters that have been pushed back). Has no effect with unbuffered reads (such as `IO#sysread`).

    f = File.new("testfile")   #=> #<File:testfile>
    c = f.getc                 #=> "8"
    f.ungetc(c)                #=> nil
    f.getc                     #=> "8"

    VALUE
    rb_io_ungetc(VALUE io, VALUE c)
    {
        rb_io_t *fptr;
        long len;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);
        if (NIL_P(c)) return Qnil;
        if (FIXNUM_P(c)) {
            c = rb_enc_uint_chr(FIX2UINT(c), io_read_encoding(fptr));
        }
        else if (RB_TYPE_P(c, T_BIGNUM)) {
            c = rb_enc_uint_chr(NUM2UINT(c), io_read_encoding(fptr));
        }
        else {
            SafeStringValue(c);
        }
        if (NEED_READCONV(fptr)) {
            SET_BINARY_MODE(fptr);
            len = RSTRING_LEN(c);
    #if SIZEOF_LONG > SIZEOF_INT
            if (len > INT_MAX)
                rb_raise(rb_eIOError, "ungetc failed");
    #endif
            make_readconv(fptr, (int)len);
            if (fptr->cbuf.capa - fptr->cbuf.len < len)
                rb_raise(rb_eIOError, "ungetc failed");
            if (fptr->cbuf.off < len) {
                MEMMOVE(fptr->cbuf.ptr+fptr->cbuf.capa-fptr->cbuf.len,
                        fptr->cbuf.ptr+fptr->cbuf.off,
                        char, fptr->cbuf.len);
                fptr->cbuf.off = fptr->cbuf.capa-fptr->cbuf.len;
            }
            fptr->cbuf.off -= (int)len;
            fptr->cbuf.len += (int)len;
            MEMMOVE(fptr->cbuf.ptr+fptr->cbuf.off, RSTRING_PTR(c), char, len);
        }
        else {
            NEED_NEWLINE_DECORATOR_ON_READ_CHECK(fptr);
            io_ungetbyte(c, fptr);
        }
        return Qnil;
    }

wait(timeout = nil, mode = :read) → IO, true or nil click to toggle source

Waits until `IO` is readable or writable without blocking and returns `self`, or `nil` when times out. Returns `true` immediately when buffered data is available. Optional parameter `mode` is one of `:read`, `:write`, or `:read_write`.

    static VALUE
    io_wait_readwrite(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        struct timeval timerec;
        struct timeval *tv = NULL;
        int event = 0;
        int i;

        GetOpenFile(io, fptr);
        for (i = 0; i < argc; ++i) {
            if (SYMBOL_P(argv[i])) {
                event |= wait_mode_sym(argv[i]);
            }
            else {
                *(tv = &timerec) = rb_time_interval(argv[i]);
            }
        }
        /* rb_time_interval() and might_mode() might convert the argument */
        rb_io_check_closed(fptr);
        if (!event) event = RB_WAITFD_IN;
        if ((event & RB_WAITFD_IN) && rb_io_read_pending(fptr))
            return Qtrue;
        if (wait_for_single_fd(fptr, event, tv))
            return io;
        return Qnil;
    }

wait_readable → IO, true or nil click to toggle source
wait_readable(timeout) → IO, true or nil

Waits until `IO` is readable without blocking and returns `self`, or `nil` when times out. Returns `true` immediately when buffered data is available.

    static VALUE
    io_wait_readable(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        struct timeval timerec;
        struct timeval *tv;

        GetOpenFile(io, fptr);
        rb_io_check_readable(fptr);
        tv = get_timeout(argc, argv, &timerec);
        if (rb_io_read_pending(fptr)) return Qtrue;
        if (wait_for_single_fd(fptr, RB_WAITFD_IN, tv)) {
            return io;
        }
        return Qnil;
    }

wait_writable → IO click to toggle source
wait_writable(timeout) → IO or nil

Waits until `IO` is writable without blocking and returns `self` or `nil` when times out.

    static VALUE
    io_wait_writable(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        struct timeval timerec;
        struct timeval *tv;

        GetOpenFile(io, fptr);
        rb_io_check_writable(fptr);
        tv = get_timeout(argc, argv, &timerec);
        if (wait_for_single_fd(fptr, RB_WAITFD_OUT, tv)) {
            return io;
        }
        return Qnil;
    }

winsize → [rows, columns] click to toggle source

Returns console size.

You must require 'io/console' to use this method.

    static VALUE
    console_winsize(VALUE io)
    {
        rb_io_t *fptr;
        int fd;
        rb_console_size_t ws;

        GetOpenFile(io, fptr);
        fd = GetWriteFD(fptr);
        if (!getwinsize(fd, &ws)) rb_sys_fail(0);
        return rb_assoc_new(INT2NUM(winsize_row(&ws)), INT2NUM(winsize_col(&ws)));
    }

winsize = [rows, columns] click to toggle source

Tries to set console size. The effect depends on the platform and the running environment.

You must require 'io/console' to use this method.

    static VALUE
    console_set_winsize(VALUE io, VALUE size)
    {
        rb_io_t *fptr;
        rb_console_size_t ws;
    #if defined _WIN32
        HANDLE wh;
        int newrow, newcol;
        BOOL ret;
    #endif
        VALUE row, col, xpixel, ypixel;
        const VALUE *sz;
        int fd;
        long sizelen;

        GetOpenFile(io, fptr);
        size = rb_Array(size);
        if ((sizelen = RARRAY_LEN(size)) != 2 && sizelen != 4) {
            rb_raise(rb_eArgError,
                     "wrong number of arguments (given %ld, expected 2 or 4)",
                     sizelen);
        }
        sz = RARRAY_CONST_PTR(size);
        row = sz[0], col = sz[1], xpixel = ypixel = Qnil;
        if (sizelen == 4) xpixel = sz[2], ypixel = sz[3];
        fd = GetWriteFD(fptr);
    #if defined TIOCSWINSZ
        ws.ws_row = ws.ws_col = ws.ws_xpixel = ws.ws_ypixel = 0;
    #define SET(m) ws.ws_##m = NIL_P(m) ? 0 : (unsigned short)NUM2UINT(m)
        SET(row);
        SET(col);
        SET(xpixel);
        SET(ypixel);
    #undef SET
        if (!setwinsize(fd, &ws)) rb_sys_fail(0);
    #elif defined _WIN32
        wh = (HANDLE)rb_w32_get_osfhandle(fd);
    #define SET(m) new##m = NIL_P(m) ? 0 : (unsigned short)NUM2UINT(m)
        SET(row);
        SET(col);
    #undef SET
        if (!NIL_P(xpixel)) (void)NUM2UINT(xpixel);
        if (!NIL_P(ypixel)) (void)NUM2UINT(ypixel);
        if (!GetConsoleScreenBufferInfo(wh, &ws)) {
            rb_syserr_fail(LAST_ERROR, "GetConsoleScreenBufferInfo");
        }
        ws.dwSize.X = newcol;
        ret = SetConsoleScreenBufferSize(wh, ws.dwSize);
        ws.srWindow.Left = 0;
        ws.srWindow.Top = 0;
        ws.srWindow.Right = newcol-1;
        ws.srWindow.Bottom = newrow-1;
        if (!SetConsoleWindowInfo(wh, TRUE, &ws.srWindow)) {
            rb_syserr_fail(LAST_ERROR, "SetConsoleWindowInfo");
        }
        /* retry when shrinking buffer after shrunk window */
        if (!ret && !SetConsoleScreenBufferSize(wh, ws.dwSize)) {
            rb_syserr_fail(LAST_ERROR, "SetConsoleScreenBufferInfo");
        }
        /* remove scrollbar if possible */
        if (!SetConsoleWindowInfo(wh, TRUE, &ws.srWindow)) {
            rb_syserr_fail(LAST_ERROR, "SetConsoleWindowInfo");
        }
    #endif
        return io;
    }

write(string, ...) → integer click to toggle source

Writes the given strings to ios. The stream must be opened for writing. Arguments that are not a string will be converted to a string using `to_s`. Returns the number of bytes written in total.

    count = $stdout.write("This is", " a test\n")
    puts "That was #{count} bytes of data"

produces:

    This is a test
    That was 15 bytes of data

    static VALUE
    io_write_m(int argc, VALUE *argv, VALUE io)
    {
        if (argc != 1) {
            return io_writev(argc, argv, io);
        }
        else {
            VALUE str = argv[0];
            return io_write(io, str, 0);
        }
    }

write_nonblock(string) → integer click to toggle source
write_nonblock(string [, options]) → integer

Writes the given string to ios using the write(2) system call after O_NONBLOCK is set for the underlying file descriptor.

It returns the number of bytes written.

`write_nonblock` just calls the write(2) system call. It causes all errors the write(2) system call causes: Errno::EWOULDBLOCK, Errno::EINTR, etc. The result may also be smaller than string.length (partial write). The caller should care such errors and partial write.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by `IO::WaitWritable`. So `IO::WaitWritable` can be used to rescue the exceptions for retrying write_nonblock.

    # Creates a pipe.
    r, w = IO.pipe

    # write_nonblock writes only 65536 bytes and return 65536.
    # (The pipe size is 65536 bytes on this environment.)
    s = "a" * 100000
    p w.write_nonblock(s)     #=> 65536

    # write_nonblock cannot write a byte and raise EWOULDBLOCK (EAGAIN).
    p w.write_nonblock("b")   # Resource temporarily unavailable (Errno::EAGAIN)

If the write buffer is not empty, it is flushed at first.

When `write_nonblock` raises an exception kind of `IO::WaitWritable`, `write_nonblock` should not be called until io is writable for avoiding busy loop. This can be done as follows.

    begin
      result = io.write_nonblock(string)
    rescue IO::WaitWritable, Errno::EINTR
      IO.select(nil, [io])
      retry
    end

Note that this doesn't guarantee to write all data in string. The length written is reported as result and it should be checked later.

On some platforms such as Windows, `write_nonblock` is not supported according to the kind of the `IO` object. In such cases, `write_nonblock` raises `Errno::EBADF`.

By specifying a keyword argument exception to `false`, you can indicate that `write_nonblock` should not raise an `IO::WaitWritable` exception, but return the symbol `:wait_writable` instead.

    # File prelude.rb, line 130
    def write_nonblock(buf, exception: true)
      __write_nonblock(buf, exception)
    end

### Private Instance Methods

block_scanf(str) { |current| ... } click to toggle source

    # File lib/scanf.rb, line 682
      def block_scanf(str)
        final = []
    # Sub-ideal, since another FS gets created in scanf.
    # But used here to determine the number of specifiers.
        fstr = Scanf::FormatString.new(str)
        last_spec = fstr.last_spec
        begin
          current = scanf(str)
          break if current.empty?
          final.push(yield(current))
        end until eof || fstr.last_spec_tried == last_spec
        return final
      end

soak_up_spaces() click to toggle source

    # File lib/scanf.rb, line 673
    def soak_up_spaces
      c = getc
      ungetc(c) if c
      until eof ||! c || /\S/.match(c.chr)
        c = getc
      end
      ungetc(c) if (c && /\S/.match(c.chr))
    end