Class: IO

Inherits:
Object show all
Includes:
Enumerable, File::Constants
Defined in:
io.c

Overview

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"

Direct Known Subclasses

File

Defined Under Namespace

Modules: WaitReadable, WaitWritable Classes: EAGAINWaitReadable, EAGAINWaitWritable, EINPROGRESSWaitReadable, EINPROGRESSWaitWritable

Constant Summary collapse

EWOULDBLOCKWaitReadable =

:EAGAINWaitReadable

same as IO
EWOULDBLOCKWaitWritable =

:EAGAINWaitWritable

same as IO
SEEK_SET =

Set I/O position from the beginning

INT2FIX(SEEK_SET)
SEEK_CUR =

Set I/O position from the current position

INT2FIX(SEEK_CUR)
SEEK_END =

Set I/O position from the end

INT2FIX(SEEK_END)
SEEK_DATA =

Set I/O position to the next location containing data

INT2FIX(SEEK_DATA)
SEEK_HOLE =

Set I/O position to the next hole

INT2FIX(SEEK_HOLE)

Constants included from File::Constants

File::Constants::APPEND, File::Constants::BINARY, File::Constants::CREAT, File::Constants::DIRECT, File::Constants::DSYNC, File::Constants::EXCL, File::Constants::LOCK_EX, File::Constants::LOCK_NB, File::Constants::LOCK_SH, File::Constants::LOCK_UN, File::Constants::NOATIME, File::Constants::NOCTTY, File::Constants::NOFOLLOW, File::Constants::NONBLOCK, File::Constants::NULL, File::Constants::RDONLY, File::Constants::RDWR, File::Constants::RSYNC, File::Constants::SHARE_DELETE, File::Constants::SYNC, File::Constants::TMPFILE, File::Constants::TRUNC, File::Constants::WRONLY

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Enumerable

#all?, #any?, #chunk, #chunk_while, #collect, #collect_concat, #count, #cycle, #detect, #drop, #drop_while, #each_cons, #each_entry, #each_slice, #each_with_index, #each_with_object, #entries, #find, #find_all, #find_index, #first, #flat_map, #grep, #grep_v, #group_by, #include?, #inject, #lazy, #map, #max, #max_by, #member?, #min, #min_by, #minmax, #minmax_by, #none?, #one?, #partition, #reduce, #reject, #reverse_each, #select, #slice_after, #slice_before, #slice_when, #sort, #sort_by, #take, #take_while, #to_a, #to_h, #zip

Constructor Details

#new(fd[, mode][, opt]) ⇒ IO

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

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. “-” is a synonym for the default external encoding.

: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.



7575
7576
7577
7578
7579
7580
7581
7582
7583
7584
7585
7586
7587
7588
7589
7590
7591
7592
7593
7594
7595
7596
7597
7598
7599
7600
7601
7602
7603
7604
7605
7606
7607
7608
7609
7610
7611
7612
7613
7614
7615
7616
7617
7618
7619
7620
7621
7622
7623
7624
7625
7626
7627
7628
7629
7630
7631
7632
 
# File 'io.c', line 7575

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) == -1) 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;
}

Class Method Details

.binread(name, [length [, offset]]) ⇒ String

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 "

Returns:



9894
9895
9896
9897
9898
9899
9900
9901
9902
9903
9904
9905
9906
9907
9908
9909
9910
9911
9912
9913
9914
9915
9916
9917
9918
9919
 
# File 'io.c', line 9894

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

    rb_scan_args(argc, argv, "12", NULL, NULL, &offset);
    FilePathValue(argv[0]);
    arg.io = rb_io_open(argv[0], rb_str_new_cstr("rb:ASCII-8BIT"), Qnil, Qnil);
    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]) ⇒ Fixnum .binwrite(name, string, [offset], open_args) ⇒ Fixnum

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

Overloads:

  • .binwrite(name, string, [offset]) ⇒ Fixnum

    Returns:

  • .binwrite(name, string, [offset], open_args) ⇒ Fixnum

    Returns:



10030
10031
10032
10033
10034
 
# File 'io.c', line 10030

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

.copy_stream(src, dst) ⇒ Object .copy_stream(src, dst, copy_length) ⇒ Object .copy_stream(src, dst, copy_length, src_offset) ⇒ Object

IO.copy_stream copies src to dst. src and dst is either a filename or an IO.

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.



10730
10731
10732
10733
10734
10735
10736
10737
10738
10739
10740
10741
10742
10743
10744
10745
10746
10747
10748
10749
10750
10751
10752
10753
10754
10755
10756
10757
 
# File 'io.c', line 10730

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_fd_init(&st.fds);
    rb_ensure(copy_stream_body, (VALUE)&st, copy_stream_finalize, (VALUE)&st);

    return OFFT2NUM(st.total);
}

.for_fd(fd, mode[, opt]) ⇒ IO

Synonym for IO.new.

Returns:



7696
7697
7698
7699
7700
7701
7702
 
# File 'io.c', line 7696

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 = $/[, open_args]) {|line| ... } ⇒ nil .foreach(name, limit[, open_args]) {|line| ... } ⇒ nil .foreach(name, sep, limit[, open_args]) {|line| ... } ⇒ nil .foreach(...) ⇒ Object

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.read for detail.

Overloads:

  • .foreach(name, sep = $/[, open_args]) {|line| ... } ⇒ nil

    Yields:

    • (line)

    Returns:

    • (nil)
  • .foreach(name, limit[, open_args]) {|line| ... } ⇒ nil

    Yields:

    • (line)

    Returns:

    • (nil)
  • .foreach(name, sep, limit[, open_args]) {|line| ... } ⇒ nil

    Yields:

    • (line)

    Returns:

    • (nil) 


9746
9747
9748
9749
9750
9751
9752
9753
9754
9755
9756
9757
9758
 
# File 'io.c', line 9746

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

    argc = rb_scan_args(argc, argv, "13:", NULL, NULL, NULL, NULL, &opt);
    RETURN_ENUMERATOR(self, orig_argc, argv);
    open_key_args(argc, argv, opt, &arg);
    if (NIL_P(arg.io)) return Qnil;
    return rb_ensure(io_s_foreach, (VALUE)&arg, rb_io_close, arg.io);
}

.new(*args) ⇒ Object

:nodoc:



7675
7676
7677
7678
7679
7680
7681
7682
7683
7684
7685
 
# File 'io.c', line 7675

static VALUE
rb_io_s_new(int argc, VALUE *argv, VALUE klass)
{
    if (rb_block_given_p()) {
	VALUE cname = rb_obj_as_string(klass);

	rb_warn("%"PRIsVALUE"::new() does not take block; use %"PRIsVALUE"::open() instead",
		cname, cname);
    }
    return rb_class_new_instance(argc, argv, klass);
}

.open(*args) ⇒ Object

call-seq:

IO.open(fd, mode="r" [, opt])                -> io
IO.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.



6378
6379
6380
6381
6382
6383
6384
6385
6386
6387
6388
 
# File 'io.c', line 6378

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 ⇒ Array .pipe(ext_enc) ⇒ Array .pipe("ext_enc: int_enc"[, opt]) ⇒ Array .pipe(ext_enc, int_enc[, opt]) ⇒ Array

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>

Overloads:



9587
9588
9589
9590
9591
9592
9593
9594
9595
9596
9597
9598
9599
9600
9601
9602
9603
9604
9605
9606
9607
9608
9609
9610
9611
9612
9613
9614
9615
9616
9617
9618
9619
9620
9621
9622
9623
9624
9625
9626
9627
9628
9629
9630
9631
9632
9633
9634
9635
9636
9637
9638
9639
9640
9641
9642
9643
9644
9645
9646
9647
9648
9649
9650
9651
9652
9653
9654
9655
9656
9657
9658
9659
9660
9661
9662
9663
9664
 
# File 'io.c', line 9587

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) == -1)
        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,], mode = "r"[, opt]) ⇒ IO .popen([env,], mode = "r"[, opt]) {|io| ... } ⇒ Object

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 contains 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;

Overloads:

  • .popen([env,], mode = "r"[, opt]) ⇒ IO

    Returns:

  • .popen([env,], mode = "r"[, opt]) {|io| ... } ⇒ Object

    Yields:

    • (io)

    Returns:



6238
6239
6240
6241
6242
6243
6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
6270
6271
6272
6273
6274
6275
6276
6277
6278
6279
6280
6281
6282
6283
6284
6285
6286
6287
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
 
# File 'io.c', line 6238

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);
	RB_GC_GUARD(tmp);
    }
    else {
	SafeStringValue(pname);
	execarg_obj = Qnil;
	if (!is_popen_fork(pname))
	    execarg_obj = rb_execarg_new(1, &pname, TRUE);
    }
    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

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.

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

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 of strings

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"

Returns:



9855
9856
9857
9858
9859
9860
9861
9862
9863
9864
9865
9866
9867
9868
9869
9870
9871
9872
9873
9874
9875
9876
9877
9878
 
# File 'io.c', line 9855

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(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 = $/[, open_args]) ⇒ Array .readlines(name, limit[, open_args]) ⇒ Array .readlines(name, sep, limit[, 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"

If the last argument is a hash, it’s the keyword argument to open. See IO.read for detail.

Overloads:

  • .readlines(name, sep = $/[, open_args]) ⇒ Array

    Returns:

  • .readlines(name, limit[, open_args]) ⇒ Array

    Returns:

  • .readlines(name, sep, limit[, open_args]) ⇒ Array

    Returns:



9784
9785
9786
9787
9788
9789
9790
9791
9792
9793
9794
 
# File 'io.c', line 9784

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

    argc = rb_scan_args(argc, argv, "13:", NULL, NULL, NULL, NULL, &opt);
    open_key_args(argc, argv, opt, &arg);
    if (NIL_P(arg.io)) return Qnil;
    return rb_ensure(io_s_readlines, (VALUE)&arg, rb_io_close, arg.io);
}

.select(read_array[, write_array [, error_array [, timeout]]]) ⇒ Array?

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 blocks.

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 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

Returns:



8833
8834
8835
8836
8837
8838
8839
8840
8841
8842
8843
8844
8845
8846
8847
8848
8849
8850
8851
8852
8853
8854
 
# File 'io.c', line 8833

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]]) ⇒ Fixnum

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

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

Returns:



6400
6401
6402
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
 
# File 'io.c', line 6400

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?

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>

Returns:

  • (IO, nil) 


718
719
720
721
722
 
# File 'io.c', line 718

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

.write(name, string, [offset]) ⇒ Fixnum .write(name, string, [offset], open_args) ⇒ Fixnum

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, the file is truncated. Otherwise, it is not truncated.

If the last argument is a hash, it specifies option for internal open(). The key would be the following. open_args: is exclusive to others.

encoding: string or encoding

 specifies encoding of the read string.  encoding will be ignored
 if length is specified.

mode: string

 specifies mode argument for open().  it should start with "w" or "a" or "r+"
 otherwise it would cause error.

perm: fixnum

 specifies perm argument for open().

open_args: array

 specifies arguments for open() as an array.

  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"

Overloads:

  • .write(name, string, [offset]) ⇒ Fixnum

    Returns:

  • .write(name, string, [offset], open_args) ⇒ Fixnum

    Returns:



10014
10015
10016
10017
10018
 
# File 'io.c', line 10014

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

Instance Method Details

#<<(obj) ⇒ IO

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

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

produces:

Hello world!

Returns:



1530
1531
1532
1533
1534
1535
 
# File 'io.c', line 1530

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

#__read_nonblock(length, str, ex) ⇒ Object (private)

:nodoc:



2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
 
# File 'io.c', line 2640

static VALUE
io_read_nonblock(VALUE io, VALUE length, VALUE str, VALUE ex)
{
    rb_io_t *fptr;
    long n, len;
    struct read_internal_arg arg;

    if ((len = NUM2LONG(length)) < 0) {
	rb_raise(rb_eArgError, "negative length %ld given", len);
    }

    io_setstrbuf(&str,len);
    OBJ_TAINT(str);
    GetOpenFile(io, fptr);
    rb_io_check_byte_readable(fptr);

    if (len == 0)
	return str;

    n = read_buffered_data(RSTRING_PTR(str), len, fptr);
    if (n <= 0) {
	rb_io_set_nonblock(fptr);
	io_setstrbuf(&str, len);
	arg.fd = fptr->fd;
	arg.str_ptr = RSTRING_PTR(str);
	arg.len = len;
	rb_str_locktmp_ensure(str, read_internal_call, (VALUE)&arg);
	n = arg.len;
        if (n < 0) {
	    int e = errno;
	    if ((e == EWOULDBLOCK || e == EAGAIN)) {
                if (ex == Qfalse) return sym_wait_readable;
		rb_readwrite_syserr_fail(RB_IO_WAIT_READABLE,
					 e, "read would block");
            }
            rb_syserr_fail_path(e, fptr->pathv);
        }
    }
    io_set_read_length(str, n);

    if (n == 0) {
	if (ex == Qfalse) return Qnil;
	rb_eof_error();
    }

    return str;
}

#__write_nonblock(str, ex) ⇒ Object (private)

:nodoc:



2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
 
# File 'io.c', line 2689

static VALUE
io_write_nonblock(VALUE io, VALUE str, VALUE ex)
{
    rb_io_t *fptr;
    long n;

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

    rb_io_set_nonblock(fptr);
    n = write(fptr->fd, RSTRING_PTR(str), RSTRING_LEN(str));

    if (n == -1) {
	int e = errno;
	if (e == EWOULDBLOCK || e == EAGAIN) {
	    if (ex == Qfalse) {
		return sym_wait_writable;
	    }
	    else {
		rb_readwrite_syserr_fail(RB_IO_WAIT_WRITABLE, e, "write would block");
	    }
	}
	rb_syserr_fail_path(e, fptr->pathv);
    }

    return LONG2FIX(n);
}

#advise(advice, offset = 0, len = 0) ⇒ nil

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.

Returns:

  • (nil) 


8668
8669
8670
8671
8672
8673
8674
8675
8676
8677
8678
8679
8680
8681
8682
8683
8684
8685
8686
8687
8688
8689
8690
 
# File 'io.c', line 8668

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) ⇒ Boolean

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

Returns:

  • (Boolean) 


7737
7738
7739
7740
7741
7742
7743
7744
7745
7746
7747
 
# File 'io.c', line 7737

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? ⇒ Boolean

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

Returns:

  • (Boolean)

Returns:

  • (Boolean) 


7712
7713
7714
7715
7716
7717
7718
 
# File 'io.c', line 7712

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;
}

#binmode ⇒ IO

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

Returns:



4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
 
# File 'io.c', line 4807

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? ⇒ Boolean

Returns true if ios is binmode.

Returns:

  • (Boolean)

Returns:

  • (Boolean) 


4826
4827
4828
4829
4830
4831
4832
 
# File 'io.c', line 4826

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

#bytes ⇒ Object

This is a deprecated alias for each_byte.



3455
3456
3457
3458
3459
3460
3461
3462
 
# File 'io.c', line 3455

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 ⇒ Object

This is a deprecated alias for each_char.



3609
3610
3611
3612
3613
3614
3615
3616
 
# File 'io.c', line 3609

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

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.

Returns:

  • (nil) 


4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
 
# File 'io.c', line 4397

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) ⇒ Boolean

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.

Returns:

  • (Boolean) 


4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
 
# File 'io.c', line 4035

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 == -1) 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 == -1) rb_sys_fail_path(fptr->pathv);
        }
    }
    return Qnil;
}

#close_on_exec? ⇒ Boolean

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

Returns:

  • (Boolean)

Returns:

  • (Boolean) 


3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
 
# File 'io.c', line 3987

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

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

Returns:

  • (nil) 


4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
 
# File 'io.c', line 4494

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

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

Returns:

  • (nil) 


4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
 
# File 'io.c', line 4554

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? ⇒ Boolean

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

Returns:

  • (Boolean)

Returns:

  • (Boolean) 


4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
 
# File 'io.c', line 4457

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 ⇒ Object

This is a deprecated alias for each_codepoint.



3737
3738
3739
3740
3741
3742
3743
3744
 
# File 'io.c', line 3737

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);
}

#each(sep = $/) {|line| ... } ⇒ IO #each(limit) {|line| ... } ⇒ IO #each(sep, limit) {|line| ... } ⇒ IO #each(...) ⇒ Object

ios.each_line(sep=$/) {|line| block } -> ios

ios.each_line(limit) {|line| block }     -> ios
ios.each_line(sep,limit) {|line| block } -> ios
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...

Overloads:

  • #each(sep = $/) {|line| ... } ⇒ IO

    Yields:

    • (line)

    Returns:

  • #each(limit) {|line| ... } ⇒ IO

    Yields:

    • (line)

    Returns:

  • #each(sep, limit) {|line| ... } ⇒ IO

    Yields:

    • (line)

    Returns:



3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
 
# File 'io.c', line 3384

static VALUE
rb_io_each_line(int argc, VALUE *argv, VALUE io)
{
    VALUE str, rs;
    long limit;

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

#each_byte {|byte| ... } ⇒ IO #each_byte ⇒ Object

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

Overloads:

  • #each_byte {|byte| ... } ⇒ IO

    Yields:

    • (byte)

    Returns:



3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
 
# File 'io.c', line 3430

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| ... } ⇒ IO #each_char ⇒ Object

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>

Overloads:

  • #each_char {|c| ... } ⇒ IO

    Yields:

    • (c)

    Returns:



3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
 
# File 'io.c', line 3586

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| ... } ⇒ IO #codepoints {|c| ... } ⇒ IO #each_codepoint ⇒ Object #codepoints ⇒ Object

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.

Overloads:

  • #each_codepoint {|c| ... } ⇒ IO

    Yields:

    • (c)

    Returns:

  • #codepoints {|c| ... } ⇒ IO

    Yields:

    • (c)

    Returns:



3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
 
# File 'io.c', line 3634

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(sep = $/) {|line| ... } ⇒ IO #each(limit) {|line| ... } ⇒ IO #each(sep, limit) {|line| ... } ⇒ IO #each(...) ⇒ Object

ios.each_line(sep=$/) {|line| block } -> ios

ios.each_line(limit) {|line| block }     -> ios
ios.each_line(sep,limit) {|line| block } -> ios
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...

Overloads:

  • #each(sep = $/) {|line| ... } ⇒ IO

    Yields:

    • (line)

    Returns:

  • #each(limit) {|line| ... } ⇒ IO

    Yields:

    • (line)

    Returns:

  • #each(sep, limit) {|line| ... } ⇒ IO

    Yields:

    • (line)

    Returns:



3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
 
# File 'io.c', line 3384

static VALUE
rb_io_each_line(int argc, VALUE *argv, VALUE io)
{
    VALUE str, rs;
    long limit;

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

#eof ⇒ Boolean #eof? ⇒ Boolean

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).

Overloads:

  • #eof ⇒ Boolean

    Returns:

    • (Boolean)
  • #eof? ⇒ Boolean

    Returns:

    • (Boolean) 


1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
 
# File 'io.c', line 1822

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 ⇒ Boolean #eof? ⇒ Boolean

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).

Overloads:

  • #eof ⇒ Boolean

    Returns:

    • (Boolean)
  • #eof? ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean) 


1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
 
# File 'io.c', line 1822

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;
}

#external_encoding ⇒ Encoding

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

Returns:



10767
10768
10769
10770
10771
10772
10773
10774
10775
10776
10777
10778
10779
10780
10781
10782
 
# File 'io.c', line 10767

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

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.

Returns:



9257
9258
9259
9260
9261
9262
9263
9264
 
# File 'io.c', line 9257

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?

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).

Returns:

  • (0, nil) 


1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
 
# File 'io.c', line 1959

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 ⇒ Fixnum #to_i ⇒ Fixnum Also known as: to_i

Returns an integer representing the numeric file descriptor for ios.

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

Overloads:



1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
 
# File 'io.c', line 1992

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);
}

#flush ⇒ IO

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

Returns:



1586
1587
1588
1589
1590
 
# File 'io.c', line 1586

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

#fsync ⇒ 0?

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).

Returns:

  • (0, nil) 


1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
 
# File 'io.c', line 1914

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 ⇒ Fixnum?

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

Returns:



3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
 
# File 'io.c', line 3808

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?

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"

Returns:



3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
 
# File 'io.c', line 3759

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);
}

#gets(sep = $/) ⇒ String? #gets(limit) ⇒ String? #gets(sep, limit) ⇒ String?

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"

Overloads:



3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
 
# File 'io.c', line 3229

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;
}

#initialize_copy(io) ⇒ Object

:nodoc:



6813
6814
6815
6816
6817
6818
6819
6820
6821
6822
6823
6824
6825
6826
6827
6828
6829
6830
6831
6832
6833
6834
6835
6836
6837
6838
6839
6840
6841
6842
6843
6844
6845
6846
6847
6848
6849
6850
6851
6852
6853
6854
6855
6856
6857
 
# File 'io.c', line 6813

static VALUE
rb_io_init_copy(VALUE dest, VALUE io)
{
    rb_io_t *fptr, *orig;
    int fd;
    VALUE write_io;
    off_t pos;

    io = rb_io_get_io(io);
    if (!OBJ_INIT_COPY(dest, io)) return dest;
    GetOpenFile(io, orig);
    MakeOpenFile(dest, fptr);

    rb_io_flush(io);

    /* copy rb_io_t structure */
    fptr->mode = orig->mode & ~FMODE_PREP;
    fptr->encs = orig->encs;
    fptr->pid = orig->pid;
    fptr->lineno = orig->lineno;
    if (!NIL_P(orig->pathv)) fptr->pathv = orig->pathv;
    fptr->finalize = orig->finalize;
#if defined (__CYGWIN__) || !defined(HAVE_WORKING_FORK)
    if (fptr->finalize == pipe_finalize)
	pipe_add_fptr(fptr);
#endif

    fd = ruby_dup(orig->fd);
    fptr->fd = fd;
    pos = io_tell(orig);
    if (0 <= pos)
        io_seek(fptr, pos, SEEK_SET);
    if (fptr->mode & FMODE_BINMODE) {
	rb_io_binmode(dest);
    }

    write_io = GetWriteIO(io);
    if (io != write_io) {
        write_io = rb_obj_dup(write_io);
        fptr->tied_io_for_writing = write_io;
        rb_ivar_set(dest, rb_intern("@tied_io_for_writing"), write_io);
    }

    return dest;
}

#inspect ⇒ String

Return a string describing this IO object.

Returns:



2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
 
# File 'io.c', line 2043

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

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

Returns:



10792
10793
10794
10795
10796
10797
10798
10799
10800
 
# File 'io.c', line 10792

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

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.

Returns:



9169
9170
9171
9172
9173
9174
9175
9176
 
# File 'io.c', line 9169

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);
}

#isatty ⇒ Boolean #tty? ⇒ Boolean

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

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

Overloads:

  • #isatty ⇒ Boolean

    Returns:

    • (Boolean)
  • #tty? ⇒ Boolean

    Returns:

    • (Boolean) 


3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
 
# File 'io.c', line 3961

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

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

Returns:



3262
3263
3264
3265
3266
3267
3268
3269
3270
 
# File 'io.c', line 3262

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

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

Returns:



3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
 
# File 'io.c', line 3289

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) ⇒ Object

This is a deprecated alias for each_line.



3404
3405
3406
3407
3408
3409
3410
3411
 
# File 'io.c', line 3404

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);
}

#pid ⇒ Fixnum

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

Returns:



2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
 
# File 'io.c', line 2024

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 #tell ⇒ Integer

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

Overloads:



1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
 
# File 'io.c', line 1605

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

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"

Returns:



1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
 
# File 'io.c', line 1699

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);
}

#print ⇒ nil #print(obj, ...) ⇒ nil

Writes the given object(s) to ios. The stream must be opened for writing. If the output field separator ($,) is not nil, it will be inserted between each object. If the output record separator ($\) is not nil, it will be appended to the output. If no arguments are given, prints $_. Objects that aren’t strings will be converted by calling their to_s method. With no argument, prints the contents of the variable $_. Returns nil.

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

produces:

This is 100 percent.

Overloads:

  • #print ⇒ nil

    Returns:

    • (nil)
  • #print(obj, ...) ⇒ nil

    Returns:

    • (nil) 


6927
6928
6929
6930
6931
6932
6933
6934
6935
6936
6937
6938
6939
6940
6941
6942
6943
6944
6945
6946
6947
6948
6949
6950
 
# File 'io.c', line 6927

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

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

Returns:

  • (nil) 


6868
6869
6870
6871
6872
6873
 
# File 'io.c', line 6868

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

#putc(obj) ⇒ Object

If obj is Numeric, write the character whose code is the least-significant byte of obj, otherwise write the first byte of the string representation of obj to ios. Note: This method is not safe for use with multi-byte characters as it will truncate them.

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

produces:

AA

Returns:



7000
7001
7002
7003
7004
7005
7006
7007
7008
7009
7010
7011
7012
7013
 
# File 'io.c', line 7000

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

Writes the given objects to ios as with IO#print. Writes a record separator (typically a newline) after any that do not already end with a newline sequence. If called with an array argument, writes each element on a new line. If called without arguments, outputs a single record separator.

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

produces:

this
is
a
test

Returns:

  • (nil) 


7092
7093
7094
7095
7096
7097
7098
7099
7100
7101
7102
7103
7104
7105
7106
7107
7108
7109
7110
7111
7112
7113
7114
7115
7116
7117
7118
7119
7120
7121
 
# File 'io.c', line 7092

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

    /* 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:
	rb_io_write(out, line);
	if (RSTRING_LEN(line) == 0 ||
            !str_end_with_asciichar(line, '\n')) {
	    rb_io_write(out, rb_default_rs);
	}
    }

    return Qnil;
}

#read([length [, outbuf]]) ⇒ String?

Reads length bytes from the I/O stream.

length must be a non-negative integer or nil.

If length is a positive integer, it tries to read length bytes without any conversion (binary mode). It returns nil or a string whose length is 1 to length bytes. nil means it met EOF at beginning. The 1 to length-1 bytes string means it met EOF after reading the result. The length bytes string means it doesn’t meet EOF. The resulted string is always ASCII-8BIT encoding.

If length is omitted or is nil, it reads until EOF and the encoding conversion is applied. It returns a string even if EOF is met at beginning.

If length is zero, it returns "".

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.

At end of file, it returns nil or "" depend on length. ios.read() and ios.read(nil) returns "". ios.read(positive-integer) returns nil.

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

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

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

# iterate over variable length records.
# record is prefixed by 32-bit length.
open("variable-record-file") {|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
}

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

Returns:



2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
 
# File 'io.c', line 2790

static VALUE
io_read(int argc, VALUE *argv, VALUE io)
{
    rb_io_t *fptr;
    long n, len;
    VALUE length, str;
#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);
    }

    io_setstrbuf(&str,len);

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

#readbyte ⇒ Fixnum

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

Returns:



3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
 
# File 'io.c', line 3841

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

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

#readchar ⇒ String

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

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

Returns:



3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
 
# File 'io.c', line 3785

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

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

#readline(sep = $/) ⇒ String #readline(limit) ⇒ String #readline(sep, limit) ⇒ String

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

Overloads:



3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
 
# File 'io.c', line 3310

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 = $/) ⇒ Array #readlines(limit) ⇒ Array #readlines(sep, limit) ⇒ Array

Reads all of the lines in ios, and returns them in anArray. 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 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"

Overloads:



3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
 
# File 'io.c', line 3339

static VALUE
rb_io_readlines(int argc, VALUE *argv, VALUE io)
{
    VALUE line, ary, rs;
    long limit;

    prepare_getline_args(argc, argv, &rs, &limit, io);
    if (limit == 0)
	rb_raise(rb_eArgError, "invalid limit: 0 for readlines");
    ary = rb_ary_new();
    while (!NIL_P(line = rb_io_getline_1(rs, limit, io))) {
	rb_ary_push(ary, line);
    }
    return ary;
}

#readpartial(maxlen) ⇒ String #readpartial(maxlen, outbuf) ⇒ Object

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.

Overloads:



2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
 
# File 'io.c', line 2619

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;
}

#reopen(other_IO) ⇒ IO #reopen(path, mode_str) ⇒ IO

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.

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"

Overloads:

  • #reopen(other_IO) ⇒ IO

    Returns:

  • #reopen(path, mode_str) ⇒ IO

    Returns:



6724
6725
6726
6727
6728
6729
6730
6731
6732
6733
6734
6735
6736
6737
6738
6739
6740
6741
6742
6743
6744
6745
6746
6747
6748
6749
6750
6751
6752
6753
6754
6755
6756
6757
6758
6759
6760
6761
6762
6763
6764
6765
6766
6767
6768
6769
6770
6771
6772
6773
6774
6775
6776
6777
6778
6779
6780
6781
6782
6783
6784
6785
6786
6787
6788
6789
6790
6791
6792
6793
6794
6795
6796
6797
6798
6799
6800
6801
6802
6803
6804
6805
6806
6807
6808
6809
6810
 
# File 'io.c', line 6724

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

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.

Returns:

  • (0) 


1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
 
# File 'io.c', line 1731

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);
}

#seek(amount, whence = IO::SEEK_SET) ⇒ 0

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"

Returns:

  • (0) 


1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
 
# File 'io.c', line 1673

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 #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.

Overloads:

  • #set_encoding(ext_enc) ⇒ IO

    Returns:

  • #set_encoding("ext_enc: int_enc") ⇒ IO

    Returns:

  • #set_encoding(ext_enc, int_enc) ⇒ IO

    Returns:

  • #set_encoding("ext_enc: int_enc", opt) ⇒ IO

    Returns:

  • #set_encoding(ext_enc, int_enc, opt) ⇒ IO

    Returns:



10821
10822
10823
10824
10825
10826
10827
10828
10829
10830
10831
10832
10833
10834
10835
 
# File 'io.c', line 10821

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_funcall2(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 ⇒ Object

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



1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
 
# File 'file.c', line 1112

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 ⇒ Boolean

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

Returns:

  • (Boolean) 


1857
1858
1859
1860
1861
1862
1863
1864
1865
 
# File 'io.c', line 1857

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=(sync) ⇒ Object 



1931
1932
1933
1934
1935
1936
 
# File 'io.c', line 1931

static VALUE
rb_io_set_sync(VALUE io, VALUE sync)
{
    rb_notimplement();
    UNREACHABLE;
}

#sysread(maxlen[, outbuf]) ⇒ String

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"

Returns:



4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
 
# File 'io.c', line 4685

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

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

    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);
    rb_str_locktmp(str);
    arg.fd = fptr->fd;
    arg.str_ptr = RSTRING_PTR(str);
    arg.len = ilen;
    rb_ensure(read_internal_call, (VALUE)&arg, rb_str_unlocktmp, str);
    n = arg.len;

    if (n == -1) {
	rb_sys_fail_path(fptr->pathv);
    }
    io_set_read_length(str, n);
    if (n == 0 && ilen > 0) {
	rb_eof_error();
    }
    OBJ_TAINT(str);

    return str;
}

#sysseek(offset, whence = IO::SEEK_SET) ⇒ Integer

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."

Returns:



4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
 
# File 'io.c', line 4600

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 == -1 && errno) rb_sys_fail_path(fptr->pathv);

    return OFFT2NUM(pos);
}

#syswrite(string) ⇒ Integer

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

Returns:



4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
 
# File 'io.c', line 4640

static VALUE
rb_io_syswrite(VALUE io, VALUE str)
{
    rb_io_t *fptr;
    long n;

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

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

    str = rb_str_new_frozen(str);

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

    n = rb_write_internal(fptr->fd, RSTRING_PTR(str), RSTRING_LEN(str));
    RB_GC_GUARD(str);

    if (n == -1) rb_sys_fail_path(fptr->pathv);

    return LONG2FIX(n);
}

#pos ⇒ Integer #tell ⇒ Integer

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

Overloads:



1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
 
# File 'io.c', line 1605

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_io ⇒ IO

Returns ios.

Returns:



2079
2080
2081
2082
2083
 
# File 'io.c', line 2079

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

#isatty ⇒ Boolean #tty? ⇒ Boolean

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

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

Overloads:

  • #isatty ⇒ Boolean

    Returns:

    • (Boolean)
  • #tty? ⇒ Boolean

    Returns:

    • (Boolean)

Returns:

  • (Boolean) 


3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
 
# File 'io.c', line 3961

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 #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

Overloads:

  • #ungetbyte(string) ⇒ nil

    Returns:

    • (nil)
  • #ungetbyte(integer) ⇒ nil

    Returns:

    • (nil) 


3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
 
# File 'io.c', line 3869

VALUE
rb_io_ungetbyte(VALUE io, VALUE b)
{
    rb_io_t *fptr;

    GetOpenFile(io, fptr);
    rb_io_check_byte_readable(fptr);
    if (NIL_P(b)) return Qnil;
    if (FIXNUM_P(b)) {
	char cc = FIX2INT(b);
	b = rb_str_new(&cc, 1);
    }
    else {
	SafeStringValue(b);
    }
    io_ungetbyte(b, fptr);
    return Qnil;
}

#ungetc(string) ⇒ nil

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"

Returns:

  • (nil) 


3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
 
# File 'io.c', line 3904

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;
}

#write(string) ⇒ Integer

Writes the given string to ios. The stream must be opened for writing. If the argument is not a string, it will be converted to a string using to_s. Returns the number of bytes written.

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

Returns:



1502
1503
1504
1505
1506
 
# File 'io.c', line 1502

static VALUE
io_write_m(VALUE io, VALUE str)
{
    return io_write(io, str, 0);
}