ARGF

Class

ARGF and `ARGV`

The ARGF object works with the array at global variable ARGV to make $stdin and file streams available in the Ruby program:

ARGV may be thought of as the argument vector array.

Initially, it contains the command-line arguments and options that are passed to the Ruby program; the program can modify that array as it likes.
ARGF may be thought of as the argument files object.

It can access file streams and/or the $stdin stream, based on what it finds in ARGV. This provides a convenient way for the command line to specify streams for a Ruby program to read.

Reading

ARGF may read from source streams, which at any particular time are determined by the content of ARGV.

Simplest Case

When the very first ARGF read occurs with an empty ARGV ([]), the source is $stdin:

File t.rb:

p ['ARGV', ARGV]
p ['ARGF.read', ARGF.read]

Commands and outputs (see below for the content of files foo.txt and bar.txt):

$ echo "Open the pod bay doors, Hal." | ruby t.rb
["ARGV", []]
["ARGF.read", "Open the pod bay doors, Hal.\n"]

$ cat foo.txt bar.txt | ruby t.rb
["ARGV", []]
["ARGF.read", "Foo 0\nFoo 1\nBar 0\nBar 1\nBar 2\nBar 3\n"]

About the Examples

Many examples here assume the existence of files foo.txt and bar.txt:

$ cat foo.txt
Foo 0
Foo 1
$ cat bar.txt
Bar 0
Bar 1
Bar 2
Bar 3

Sources in `ARGV`

For any ARGF read except the simplest case (that is, except for the very first ARGF read with an empty ARGV), the sources are found in ARGV.

ARGF assumes that each element in array ARGV is a potential source, and is one of:

The string path to a file that may be opened as a stream.
The character '-', meaning stream $stdin.

Each element that is not one of these should be removed from ARGV before ARGF accesses that source.

In the following example:

Filepaths foo.txt and bar.txt may be retained as potential sources.
Options --xyzzy and --mojo should be removed.

Example:

File t.rb:

# Print arguments (and options, if any) found on command line.
p ['ARGV', ARGV]

Command and output:

$ ruby t.rb --xyzzy --mojo foo.txt bar.txt
["ARGV", ["--xyzzy", "--mojo", "foo.txt", "bar.txt"]]

ARGF’s stream access considers the elements of ARGV, left to right:

File t.rb:

p "ARGV: #{ARGV}"
p "Line: #{ARGF.read}" # Read everything from all specified streams.

Command and output:

$ ruby t.rb foo.txt bar.txt
"ARGV: [\"foo.txt\", \"bar.txt\"]"
"Read: Foo 0\nFoo 1\nBar 0\nBar 1\nBar 2\nBar 3\n"

Because the value at ARGV is an ordinary array, you can manipulate it to control which sources ARGF considers:

If you remove an element from ARGV, ARGF will not consider the corresponding source.
If you add an element to ARGV, ARGF will consider the corresponding source.

Each element in ARGV is removed when its corresponding source is accessed; when all sources have been accessed, the array is empty:

File t.rb:

until ARGV.empty? && ARGF.eof?
  p "ARGV: #{ARGV}"
  p "Line: #{ARGF.readline}" # Read each line from each specified stream.
end

Command and output:

$ ruby t.rb foo.txt bar.txt
"ARGV: [\"foo.txt\", \"bar.txt\"]"
"Line: Foo 0\n"
"ARGV: [\"bar.txt\"]"
"Line: Foo 1\n"
"ARGV: [\"bar.txt\"]"
"Line: Bar 0\n"
"ARGV: []"
"Line: Bar 1\n"
"ARGV: []"
"Line: Bar 2\n"
"ARGV: []"
"Line: Bar 3\n"

Filepaths in `ARGV`

The ARGV array may contain filepaths the specify sources for ARGF reading.

This program prints what it reads from files at the paths specified on the command line:

File t.rb:

p ['ARGV', ARGV]
# Read and print all content from the specified sources.
p ['ARGF.read', ARGF.read]

Command and output:

$ ruby t.rb foo.txt bar.txt
["ARGV", [foo.txt, bar.txt]
["ARGF.read", "Foo 0\nFoo 1\nBar 0\nBar 1\nBar 2\nBar 3\n"]

Specifying `$stdin` in `ARGV`

To specify stream $stdin in ARGV, us the character '-':

File t.rb:

p ['ARGV', ARGV]
p ['ARGF.read', ARGF.read]

Command and output:

$ echo "Open the pod bay doors, Hal." | ruby t.rb -
["ARGV", ["-"]]
["ARGF.read", "Open the pod bay doors, Hal.\n"]

When no character '-' is given, stream $stdin is ignored (exception: see Specifying $stdin in ARGV):

Command and output:

$ echo "Open the pod bay doors, Hal." | ruby t.rb foo.txt bar.txt
"ARGV: [\"foo.txt\", \"bar.txt\"]"
"Read: Foo 0\nFoo 1\nBar 0\nBar 1\nBar 2\nBar 3\n"

Mixtures and Repetitions in `ARGV`

For an ARGF reader, ARGV may contain any mixture of filepaths and character '-', including repetitions.

Modifications to `ARGV`

The running Ruby program may make any modifications to the ARGV array; the current value of ARGV affects ARGF reading.

Empty `ARGV`

For an empty ARGV, an ARGF read method either returns nil or raises an exception, depending on the specific method.

About Enumerable

ARGF includes module Enumerable. Virtually all methods in Enumerable call method #each in the including class.

Note well: In ARGF, method each returns data from the sources, not from ARGV; therefore, for example, ARGF#entries returns an array of lines from the sources, not an array of the strings from ARGV:

File t.rb:

p ['ARGV', ARGV]
p ['ARGF.entries', ARGF.entries]

Command and output:

$ ruby t.rb foo.txt bar.txt
["ARGV", ["foo.txt", "bar.txt"]]
["ARGF.entries", ["Foo 0\n", "Foo 1\n", "Bar 0\n", "Bar 1\n", "Bar 2\n", "Bar 3\n"]]

Writing

If inplace mode is in effect, ARGF may write to target streams, which at any particular time are determined by the content of ARGV.

Methods about inplace mode:

Methods for writing:

Instance Methods

ARGF.argv → ARGV

io.c View on GitHub

          
            static VALUE
argf_argv(VALUE argf)
{
    return ARGF.argv;
}

Returns the ARGV array, which contains the arguments passed to your script, one per element.

For example:

$ ruby argf.rb -v glark.txt

ARGF.argv   #=> ["-v", "glark.txt"]

ARGF.binmode → ARGF

io.c View on GitHub

          
            static VALUE
argf_binmode_m(VALUE argf)
{
    ARGF.binmode = 1;
    next_argv();
    ARGF_FORWARD(0, 0);
    rb_io_ascii8bit_binmode(ARGF.current_file);
    return argf;
}

Puts ARGF into binary mode. Once a stream is in binary mode, it cannot be reset to non-binary mode. This option has the following effects:

Newline conversion is disabled.
Encoding conversion is disabled.
Content is treated as ASCII-8BIT.

ARGF.binmode? → true or false

io.c View on GitHub

          
            static VALUE
argf_binmode_p(VALUE argf)
{
    return RBOOL(ARGF.binmode);
}

Returns true if ARGF is being read in binary mode; false otherwise. To enable binary mode use ARGF.binmode.

For example:

ARGF.binmode?  #=> false
ARGF.binmode
ARGF.binmode?  #=> true

ARGF.close → ARGF

io.c View on GitHub

          
            static VALUE
argf_close_m(VALUE argf)
{
    next_argv();
    argf_close(argf);
    if (ARGF.next_p != -1) {
        ARGF.next_p = 1;
    }
    ARGF.lineno = 0;
    return argf;
}

Closes the current file and skips to the next file in ARGV. If there are no more files to open, just closes the current file. STDIN will not be closed.

For example:

$ ruby argf.rb foo bar

ARGF.filename  #=> "foo"
ARGF.close
ARGF.filename  #=> "bar"
ARGF.close

ARGF.closed? → true or false

io.c View on GitHub

          
            static VALUE
argf_closed(VALUE argf)
{
    next_argv();
    ARGF_FORWARD(0, 0);
    return rb_io_closed_p(ARGF.current_file);
}

Returns true if the current file has been closed; false otherwise. Use ARGF.close to actually close the current file.

ARGF.each(sep=$/) {|line| block } → ARGF

ARGF.each(sep=$/, limit) {|line| block } → ARGF

ARGF.each(...) → an_enumerator

io.c View on GitHub

          
            static VALUE
argf_each_line(int argc, VALUE *argv, VALUE argf)
{
    RETURN_ENUMERATOR(argf, argc, argv);
    FOREACH_ARGF() {
        argf_block_call_line(rb_intern("each_line"), argc, argv, argf);
    }
    return argf;
}

Returns an enumerator which iterates over each line (separated by sep, which defaults to your platform’s newline character) of each file in ARGV. If a block is supplied, each line in turn will be yielded to the block, otherwise an enumerator is returned. The optional limit argument is an Integer specifying the maximum length of each line; longer lines will be split according to this limit.

This method allows you to treat the files supplied on the command line as a single file consisting of the concatenation of each named file. After the last line of the first file has been returned, the first line of the second file is returned. The ARGF.filename and ARGF.lineno methods can be used to determine the filename of the current line and line number of the whole input, respectively.

For example, the following code prints out each line of each named file prefixed with its line number, displaying the filename once per file:

ARGF.each_line do |line|
  puts ARGF.filename if ARGF.file.lineno == 1
  puts "#{ARGF.file.lineno}: #{line}"
end

While the following code prints only the first file’s name at first, and the contents with line number counted through all named files.

ARGF.each_line do |line|
  puts ARGF.filename if ARGF.lineno == 1
  puts "#{ARGF.lineno}: #{line}"
end

ARGF.each_byte {|byte| block } → ARGF

ARGF.each_byte → an_enumerator

io.c View on GitHub

          
            static VALUE
argf_each_byte(VALUE argf)
{
    RETURN_ENUMERATOR(argf, 0, 0);
    FOREACH_ARGF() {
        argf_block_call(rb_intern("each_byte"), 0, 0, argf);
    }
    return argf;
}

Iterates over each byte of each file in ARGV. A byte is returned as an Integer in the range 0..255.

This method allows you to treat the files supplied on the command line as a single file consisting of the concatenation of each named file. After the last byte of the first file has been returned, the first byte of the second file is returned. The ARGF.filename method can be used to determine the filename of the current byte.

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

For example:

ARGF.bytes.to_a  #=> [35, 32, ... 95, 10]

ARGF.each_char {|char| block } → ARGF

ARGF.each_char → an_enumerator

io.c View on GitHub

          
            static VALUE
argf_each_char(VALUE argf)
{
    RETURN_ENUMERATOR(argf, 0, 0);
    FOREACH_ARGF() {
        argf_block_call(rb_intern("each_char"), 0, 0, argf);
    }
    return argf;
}

Iterates over each character of each file in ARGF.

This method allows you to treat the files supplied on the command line as a single file consisting of the concatenation of each named file. After the last character of the first file has been returned, the first character of the second file is returned. The ARGF.filename method can be used to determine the name of the file in which the current character appears.

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

ARGF.each_codepoint {|codepoint| block } → ARGF

ARGF.each_codepoint → an_enumerator

io.c View on GitHub

          
            static VALUE
argf_each_codepoint(VALUE argf)
{
    RETURN_ENUMERATOR(argf, 0, 0);
    FOREACH_ARGF() {
        argf_block_call(rb_intern("each_codepoint"), 0, 0, argf);
    }
    return argf;
}

Iterates over each codepoint of each file in ARGF.

This method allows you to treat the files supplied on the command line as a single file consisting of the concatenation of each named file. After the last codepoint of the first file has been returned, the first codepoint of the second file is returned. The ARGF.filename method can be used to determine the name of the file in which the current codepoint appears.

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

ARGF.each_line(sep=$/) {|line| block } → ARGF

ARGF.each_line(sep=$/, limit) {|line| block } → ARGF

ARGF.each_line(...) → an_enumerator

io.c View on GitHub

An alias for each

ARGF.eof → true or false

io.c View on GitHub

          
            static VALUE
argf_eof(VALUE argf)
{
    next_argv();
    if (RTEST(ARGF.current_file)) {
        if (ARGF.init_p == 0) return Qtrue;
        next_argv();
        ARGF_FORWARD(0, 0);
        if (rb_io_eof(ARGF.current_file)) {
            return Qtrue;
        }
    }
    return Qfalse;
}

Returns true if the current file in ARGF is at end of file, i.e. it has no data to read. The stream must be opened for reading or an IOError will be raised.

$ echo "eof" | ruby argf.rb

ARGF.eof?                 #=> false
3.times { ARGF.readchar }
ARGF.eof?                 #=> false
ARGF.readchar             #=> "\n"
ARGF.eof?                 #=> true

ARGF.eof? → true or false

io.c View on GitHub

An alias for eof

ARGF.external_encoding → encoding

io.c View on GitHub

          
            static VALUE
argf_external_encoding(VALUE argf)
{
    return argf_encoding(argf, rb_io_external_encoding);
}

Returns the external encoding for files read from ARGF as an Encoding object. The external encoding is the encoding of the text as stored in a file. Contrast with ARGF.internal_encoding, which is the encoding used to represent this text within Ruby.

To set the external encoding use ARGF.set_encoding.

For example:

ARGF.external_encoding  #=>  #<Encoding:UTF-8>

ARGF.file → IO or File object

io.c View on GitHub

          
            static VALUE
argf_file(VALUE argf)
{
    next_argv();
    return ARGF.current_file;
}

Returns the current file as an IO or File object. $stdin is returned when the current file is STDIN.

For example:

$ echo "foo" > foo
$ echo "bar" > bar

$ ruby argf.rb foo bar

ARGF.file      #=> #<File:foo>
ARGF.read(5)   #=> "foo\nb"
ARGF.file      #=> #<File:bar>

ARGF.filename → String

io.c View on GitHub

          
            static VALUE
argf_filename(VALUE argf)
{
    next_argv();
    return ARGF.filename;
}

Returns the current filename. “-” is returned when the current file is STDIN.

For example:

$ echo "foo" > foo
$ echo "bar" > bar
$ echo "glark" > glark

$ ruby argf.rb foo bar glark

ARGF.filename  #=> "foo"
ARGF.read(5)   #=> "foo\nb"
ARGF.filename  #=> "bar"
ARGF.skip
ARGF.filename  #=> "glark"

ARGF.fileno → integer

io.c View on GitHub

          
            static VALUE
argf_fileno(VALUE argf)
{
    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream");
    }
    ARGF_FORWARD(0, 0);
    return rb_io_fileno(ARGF.current_file);
}

Returns an integer representing the numeric file descriptor for the current file. Raises an ArgumentError if there isn’t a current file.

ARGF.fileno    #=> 3

ARGF.getbyte → Integer or nil

io.c View on GitHub

          
            static VALUE
argf_getbyte(VALUE argf)
{
    VALUE ch;

  retry:
    if (!next_argv()) return Qnil;
    if (!RB_TYPE_P(ARGF.current_file, T_FILE)) {
        ch = forward_current(rb_intern("getbyte"), 0, 0);
    }
    else {
        ch = rb_io_getbyte(ARGF.current_file);
    }
    if (NIL_P(ch) && ARGF.next_p != -1) {
        argf_close(argf);
        ARGF.next_p = 1;
        goto retry;
    }

    return ch;
}

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

For example:

$ echo "foo" > file
$ ruby argf.rb file

ARGF.getbyte #=> 102
ARGF.getbyte #=> 111
ARGF.getbyte #=> 111
ARGF.getbyte #=> 10
ARGF.getbyte #=> nil

ARGF.getc → String or nil

io.c View on GitHub

          
            static VALUE
argf_getc(VALUE argf)
{
    VALUE ch;

  retry:
    if (!next_argv()) return Qnil;
    if (ARGF_GENERIC_INPUT_P()) {
        ch = forward_current(rb_intern("getc"), 0, 0);
    }
    else {
        ch = rb_io_getc(ARGF.current_file);
    }
    if (NIL_P(ch) && ARGF.next_p != -1) {
        argf_close(argf);
        ARGF.next_p = 1;
        goto retry;
    }

    return ch;
}

Reads the next character from ARGF and returns it as a String. Returns nil at the end of the stream.

ARGF treats the files named on the command line as a single file created by concatenating their contents. After returning the last character of the first file, it returns the first character of the second file, and so on.

For example:

$ echo "foo" > file
$ ruby argf.rb file

ARGF.getc  #=> "f"
ARGF.getc  #=> "o"
ARGF.getc  #=> "o"
ARGF.getc  #=> "\n"
ARGF.getc  #=> nil
ARGF.getc  #=> nil

ARGF.gets(sep=$/ [, getline_args]) → string or nil

ARGF.gets(limit [, getline_args]) → string or nil

ARGF.gets(sep, limit [, getline_args]) → string or nil

io.c View on GitHub

          
            static VALUE
argf_gets(int argc, VALUE *argv, VALUE argf)
{
    VALUE line;

    line = argf_getline(argc, argv, argf);
    rb_lastline_set(line);

    return line;
}

Returns the next line from the current file in ARGF.

By default lines are assumed to be separated by $/; to use a different character as a separator, supply it as a String for the sep argument.

The optional limit argument specifies how many characters of each line to return. By default all characters are returned.

See IO.readlines for details about getline_args.

ARGF.inplace_mode → String

io.c View on GitHub

          
            static VALUE
argf_inplace_mode_get(VALUE argf)
{
    if (!ARGF.inplace) return Qnil;
    if (NIL_P(ARGF.inplace)) return rb_str_new(0, 0);
    return rb_str_dup(ARGF.inplace);
}

Returns the file extension appended to the names of backup copies of modified files under in-place edit mode. This value can be set using ARGF.inplace_mode= or passing the -i switch to the Ruby binary.

ARGF.inplace_mode = ext → ARGF

io.c View on GitHub

          
            static VALUE
argf_inplace_mode_set(VALUE argf, VALUE val)
{
    if (!RTEST(val)) {
        ARGF.inplace = Qfalse;
    }
    else if (StringValueCStr(val), !RSTRING_LEN(val)) {
        ARGF.inplace = Qnil;
    }
    else {
        ARGF.inplace = rb_str_new_frozen(val);
    }
    return argf;
}

Sets the filename extension for in-place editing mode to the given String. The backup copy of each file being edited has this value appended to its filename.

For example:

$ ruby argf.rb file.txt

ARGF.inplace_mode = '.bak'
ARGF.each_line do |line|
  print line.sub("foo","bar")
end

First, file.txt.bak is created as a backup copy of file.txt. Then, each line of file.txt has the first occurrence of “foo” replaced with “bar”.

inspect

io.c View on GitHub

An alias for to_s

ARGF.internal_encoding → encoding

io.c View on GitHub

          
            static VALUE
argf_internal_encoding(VALUE argf)
{
    return argf_encoding(argf, rb_io_internal_encoding);
}

Returns the internal encoding for strings read from ARGF as an Encoding object.

If ARGF.set_encoding has been called with two encoding names, the second is returned. Otherwise, if Encoding.default_external has been set, that value is returned. Failing that, if a default external encoding was specified on the command-line, that value is used. If the encoding is unknown, nil is returned.

ARGF.lineno → integer

io.c View on GitHub

          
            static VALUE
argf_lineno(VALUE argf)
{
    return INT2FIX(ARGF.lineno);
}

Returns the current line number of ARGF as a whole. This value can be set manually with ARGF.lineno=.

For example:

ARGF.lineno   #=> 0
ARGF.readline #=> "This is line 1\n"
ARGF.lineno   #=> 1

ARGF.lineno = integer → integer

io.c View on GitHub

          
            static VALUE
argf_set_lineno(VALUE argf, VALUE val)
{
    ARGF.lineno = NUM2INT(val);
    ARGF.last_lineno = ARGF.lineno;
    return val;
}

Sets the line number of ARGF as a whole to the given Integer.

ARGF sets the line number automatically as you read data, so normally you will not need to set it explicitly. To access the current line number use ARGF.lineno.

For example:

ARGF.lineno      #=> 0
ARGF.readline    #=> "This is line 1\n"
ARGF.lineno      #=> 1
ARGF.lineno = 0  #=> 0
ARGF.lineno      #=> 0

ARGF.path → String

io.c View on GitHub

An alias for filename

ARGF.pos → Integer

io.c View on GitHub

An alias for tell

ARGF.pos = position → Integer

io.c View on GitHub

          
            static VALUE
argf_set_pos(VALUE argf, VALUE offset)
{
    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream to set position");
    }
    ARGF_FORWARD(1, &offset);
    return rb_io_set_pos(ARGF.current_file, offset);
}

Seeks to the position given by position (in bytes) in ARGF.

For example:

ARGF.pos = 17
ARGF.gets   #=> "This is line two\n"

print(*objects) → nil

io.c View on GitHub

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

    /* if no argument given, print `$_' */
    if (argc == 0) {
        argc = 1;
        line = rb_lastline_get();
        argv = &line;
    }
    if (argc > 1 && !NIL_P(rb_output_fs)) {
        rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "$, is set to non-nil value");
    }
    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;
}

Writes the given objects to the stream; returns nil. Appends the output record separator $OUTPUT_RECORD_SEPARATOR ($\), if it is not nil. See Line IO.

With argument objects given, for each object:

Converts via its method to_s if not a string.
Writes to the stream.
If not the last object, writes the output field separator $OUTPUT_FIELD_SEPARATOR ($,) if it is not nil.

With default separators:

f = File.open('t.tmp', 'w+')
objects = [0, 0.0, Rational(0, 1), Complex(0, 0), :zero, 'zero']
p $OUTPUT_RECORD_SEPARATOR
p $OUTPUT_FIELD_SEPARATOR
f.print(*objects)
f.rewind
p f.read
f.close

Output:

nil
nil
"00.00/10+0izerozero"

With specified separators:

$\ = "\n"
$, = ','
f.rewind
f.print(*objects)
f.rewind
p f.read

Output:

"0,0.0,0/1,0+0i,zero,zero\n"

With no argument given, writes the content of $_ (which is usually the most recent user input):

f = File.open('t.tmp', 'w+')
gets # Sets $_ to the most recent user input.
f.print
f.close

printf(format_string, *objects) → nil

io.c View on GitHub

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

Formats and writes objects to the stream.

For details on format_string, see Format Specifications.

putc(object) → object

io.c View on GitHub

          
            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;
}

Writes a character to the stream. See Character IO.

If object is numeric, converts to integer if necessary, then writes the character whose code is the least significant byte; if object is a string, writes the first character:

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

Output:

AA

puts(*objects) → nil

io.c View on GitHub

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

    /* if no argument given, print newline. */
    if (argc == 0) {
        rb_io_write(out, rb_default_rs);
        return Qnil;
    }
    for (int i = 0; i < argc; i++) {
        // Convert the argument to a string:
        if (RB_TYPE_P(argv[i], T_STRING)) {
            line = argv[i];
        }
        else if (rb_exec_recursive(io_puts_ary, argv[i], out)) {
            continue;
        }
        else {
            line = rb_obj_as_string(argv[i]);
        }

        // Write the line:
        int n = 0;
        if (RSTRING_LEN(line) == 0) {
            args[n++] = rb_default_rs;
        }
        else {
            args[n++] = line;
            if (!rb_str_end_with_asciichar(line, '\n')) {
                args[n++] = rb_default_rs;
            }
        }

        rb_io_writev(out, n, args);
    }

    return Qnil;
}

Writes the given objects to the stream, which must be open for writing; returns nil.\ Writes a newline after each that does not already end with a newline sequence. If called without arguments, writes a newline. See Line IO.

Note that each added newline is the character "\n"<//tt>, not the output record separator (<tt>$\).

Treatment for each object:

String: writes the string.
Neither string nor array: writes object.to_s.
Array: writes each element of the array; arrays may be nested.

To keep these examples brief, we define this helper method:

def show(*objects)
  # Puts objects to file.
  f = File.new('t.tmp', 'w+')
  f.puts(objects)
  # Return file content.
  f.rewind
  p f.read
  f.close
end

# Strings without newlines.
show('foo', 'bar', 'baz')     # => "foo\nbar\nbaz\n"
# Strings, some with newlines.
show("foo\n", 'bar', "baz\n") # => "foo\nbar\nbaz\n"

# Neither strings nor arrays:
show(0, 0.0, Rational(0, 1), Complex(9, 0), :zero)
# => "0\n0.0\n0/1\n9+0i\nzero\n"

# Array of strings.
show(['foo', "bar\n", 'baz']) # => "foo\nbar\nbaz\n"
# Nested arrays.
show([[[0, 1], 2, 3], 4, 5])  # => "0\n1\n2\n3\n4\n5\n"

ARGF.read([length [, outbuf]]) → string, outbuf, or nil

io.c View on GitHub

          
            static VALUE
argf_read(int argc, VALUE *argv, VALUE argf)
{
    VALUE tmp, str, length;
    long len = 0;

    rb_scan_args(argc, argv, "02", &length, &str);
    if (!NIL_P(length)) {
        len = NUM2LONG(argv[0]);
    }
    if (!NIL_P(str)) {
        StringValue(str);
        rb_str_resize(str,0);
        argv[1] = Qnil;
    }

  retry:
    if (!next_argv()) {
        return str;
    }
    if (ARGF_GENERIC_INPUT_P()) {
        tmp = argf_forward(argc, argv, argf);
    }
    else {
        tmp = io_read(argc, argv, ARGF.current_file);
    }
    if (NIL_P(str)) str = tmp;
    else if (!NIL_P(tmp)) rb_str_append(str, tmp);
    if (NIL_P(tmp) || NIL_P(length)) {
        if (ARGF.next_p != -1) {
            argf_close(argf);
            ARGF.next_p = 1;
            goto retry;
        }
    }
    else if (argc >= 1) {
        long slen = RSTRING_LEN(str);
        if (slen < len) {
            argv[0] = LONG2NUM(len - slen);
            goto retry;
        }
    }
    return str;
}

Reads length bytes from ARGF. The files named on the command line are concatenated and treated as a single file by this method, so when called without arguments the contents of this pseudo file are returned in their entirety.

length must be a non-negative integer or nil.

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

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

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

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

For example:

$ echo "small" > small.txt
$ echo "large" > large.txt
$ ./glark.rb small.txt large.txt

ARGF.read      #=> "small\nlarge"
ARGF.read(200) #=> "small\nlarge"
ARGF.read(2)   #=> "sm"
ARGF.read(0)   #=> ""

Note that this method behaves like the fread() function in C. This means it retries to invoke read(2) system calls to read data with the specified length. If you need the behavior like a single read(2) system call, consider ARGF#readpartial or ARGF#read_nonblock.

ARGF.read_nonblock(maxlen[, options]) → string

ARGF.read_nonblock(maxlen, outbuf[, options]) → outbuf

io.c View on GitHub

          
            static VALUE
argf_read_nonblock(int argc, VALUE *argv, VALUE argf)
{
    VALUE opts;

    rb_scan_args(argc, argv, "11:", NULL, NULL, &opts);

    if (!NIL_P(opts))
        argc--;

    return argf_getpartial(argc, argv, argf, opts, 1);
}

Reads at most maxlen bytes from the ARGF stream in non-blocking mode.

ARGF.readbyte → Integer

io.c View on GitHub

          
            static VALUE
argf_readbyte(VALUE argf)
{
    VALUE c;

    NEXT_ARGF_FORWARD(0, 0);
    c = argf_getbyte(argf);
    if (NIL_P(c)) {
        rb_eof_error();
    }
    return c;
}

Reads the next 8-bit byte from ARGF and returns it as an Integer. Raises an EOFError after the last byte of the last file has been read.

For example:

$ echo "foo" > file
$ ruby argf.rb file

ARGF.readbyte  #=> 102
ARGF.readbyte  #=> 111
ARGF.readbyte  #=> 111
ARGF.readbyte  #=> 10
ARGF.readbyte  #=> end of file reached (EOFError)

ARGF.readchar → String or nil

io.c View on GitHub

          
            static VALUE
argf_readchar(VALUE argf)
{
    VALUE ch;

  retry:
    if (!next_argv()) rb_eof_error();
    if (!RB_TYPE_P(ARGF.current_file, T_FILE)) {
        ch = forward_current(rb_intern("getc"), 0, 0);
    }
    else {
        ch = rb_io_getc(ARGF.current_file);
    }
    if (NIL_P(ch) && ARGF.next_p != -1) {
        argf_close(argf);
        ARGF.next_p = 1;
        goto retry;
    }

    return ch;
}

Reads the next character from ARGF and returns it as a String. Raises an EOFError after the last character of the last file has been read.

For example:

$ echo "foo" > file
$ ruby argf.rb file

ARGF.readchar  #=> "f"
ARGF.readchar  #=> "o"
ARGF.readchar  #=> "o"
ARGF.readchar  #=> "\n"
ARGF.readchar  #=> end of file reached (EOFError)

ARGF.readline(sep=$/) → string

ARGF.readline(limit) → string

ARGF.readline(sep, limit) → string

io.c View on GitHub

          
            static VALUE
argf_readline(int argc, VALUE *argv, VALUE argf)
{
    VALUE line;

    if (!next_argv()) rb_eof_error();
    ARGF_FORWARD(argc, argv);
    line = argf_gets(argc, argv, argf);
    if (NIL_P(line)) {
        rb_eof_error();
    }

    return line;
}

Returns the next line from the current file in ARGF.

By default lines are assumed to be separated by $/; to use a different character as a separator, supply it as a String for the sep argument.

The optional limit argument specifies how many characters of each line to return. By default all characters are returned.

An EOFError is raised at the end of the file.

ARGF.readlines(sep = $/, chomp: false) → array

ARGF.readlines(limit, chomp: false) → array

ARGF.readlines(sep, limit, chomp: false) → array

io.c View on GitHub

          
            static VALUE
argf_readlines(int argc, VALUE *argv, VALUE argf)
{
    long lineno = ARGF.lineno;
    VALUE lines, ary;

    ary = rb_ary_new();
    while (next_argv()) {
        if (ARGF_GENERIC_INPUT_P()) {
            lines = forward_current(rb_intern("readlines"), argc, argv);
        }
        else {
            lines = rb_io_readlines(argc, argv, ARGF.current_file);
            argf_close(argf);
        }
        ARGF.next_p = 1;
        rb_ary_concat(ary, lines);
        ARGF.lineno = lineno + RARRAY_LEN(ary);
        ARGF.last_lineno = ARGF.lineno;
    }
    ARGF.init_p = 0;
    return ary;
}

Reads each file in ARGF in its entirety, returning an Array containing lines from the files. Lines are assumed to be separated by sep.

lines = ARGF.readlines
lines[0]                #=> "This is line one\n"

See IO.readlines for a full description of all options.

ARGF.readpartial(maxlen) → string

ARGF.readpartial(maxlen, outbuf) → outbuf

io.c View on GitHub

          
            static VALUE
argf_readpartial(int argc, VALUE *argv, VALUE argf)
{
    return argf_getpartial(argc, argv, argf, Qnil, 0);
}

Reads at most maxlen bytes from the ARGF stream.

It raises EOFError on end of ARGF stream. Since ARGF stream is a concatenation of multiple files, internally EOF is occur for each file. ARGF.readpartial returns empty strings for EOFs except the last one and raises EOFError for the last one.

ARGF.rewind → 0

io.c View on GitHub

          
            static VALUE
argf_rewind(VALUE argf)
{
    VALUE ret;
    int old_lineno;

    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream to rewind");
    }
    ARGF_FORWARD(0, 0);
    old_lineno = RFILE(ARGF.current_file)->fptr->lineno;
    ret = rb_io_rewind(ARGF.current_file);
    if (!global_argf_p(argf)) {
        ARGF.last_lineno = ARGF.lineno -= old_lineno;
    }
    return ret;
}

Positions the current file to the beginning of input, resetting ARGF.lineno to zero.

ARGF.readline   #=> "This is line one\n"
ARGF.rewind     #=> 0
ARGF.lineno     #=> 0
ARGF.readline   #=> "This is line one\n"

ARGF.seek(amount, whence=IO::SEEK_SET) → 0

io.c View on GitHub

          
            static VALUE
argf_seek_m(int argc, VALUE *argv, VALUE argf)
{
    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream to seek");
    }
    ARGF_FORWARD(argc, argv);
    return rb_io_seek_m(argc, argv, ARGF.current_file);
}

Seeks to offset amount (an Integer) in the ARGF stream according to the value of whence. See IO#seek for further details.

ARGF.set_encoding(ext_enc) → ARGF

ARGF.set_encoding("ext_enc:int_enc") → ARGF

ARGF.set_encoding(ext_enc, int_enc) → ARGF

ARGF.set_encoding("ext_enc:int_enc", opt) → ARGF

ARGF.set_encoding(ext_enc, int_enc, opt) → ARGF

io.c View on GitHub

          
            static VALUE
argf_set_encoding(int argc, VALUE *argv, VALUE argf)
{
    rb_io_t *fptr;

    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream to set encoding");
    }
    rb_io_set_encoding(argc, argv, ARGF.current_file);
    GetOpenFile(ARGF.current_file, fptr);
    ARGF.encs = fptr->encs;
    return argf;
}

If single argument is specified, strings read from ARGF are tagged with the encoding specified.

If two encoding names separated by a colon are given, e.g. “ascii:utf-8”, the read string is converted from the first encoding (external encoding) to the second encoding (internal encoding), then tagged with the second encoding.

If two arguments are specified, they must be encoding objects or encoding names. Again, the first specifies the external encoding; the second specifies the internal encoding.

If the external encoding and the internal encoding are specified, the optional Hash argument can be used to adjust the conversion process. The structure of this hash is explained in the String#encode documentation.

For example:

ARGF.set_encoding('ascii')         # Tag the input as US-ASCII text
ARGF.set_encoding(Encoding::UTF_8) # Tag the input as UTF-8 text
ARGF.set_encoding('utf-8','ascii') # Transcode the input from US-ASCII
                                   # to UTF-8.

ARGF.skip → ARGF

io.c View on GitHub

          
            static VALUE
argf_skip(VALUE argf)
{
    if (ARGF.init_p && ARGF.next_p == 0) {
        argf_close(argf);
        ARGF.next_p = 1;
    }
    return argf;
}

Sets the current file to the next file in ARGV. If there aren’t any more files it has no effect.

For example:

$ ruby argf.rb foo bar
ARGF.filename  #=> "foo"
ARGF.skip
ARGF.filename  #=> "bar"

ARGF.tell → Integer

io.c View on GitHub

          
            static VALUE
argf_tell(VALUE argf)
{
    if (!next_argv()) {
        rb_raise(rb_eArgError, "no stream to tell");
    }
    ARGF_FORWARD(0, 0);
    return rb_io_tell(ARGF.current_file);
}

Returns the current offset (in bytes) of the current file in ARGF.

ARGF.pos    #=> 0
ARGF.gets   #=> "This is line one\n"
ARGF.pos    #=> 17

          
            static VALUE
argf_to_io(VALUE argf)
{
    next_argv();
    ARGF_FORWARD(0, 0);
    return ARGF.current_file;
}

Returns an IO object representing the current file. This will be a File object unless the current file is a stream such as STDIN.

For example:

ARGF.to_io    #=> #<File:glark.txt>
ARGF.to_io    #=> #<IO:<STDIN>>

ARGF.to_s → String

io.c View on GitHub

          
            static VALUE
argf_to_s(VALUE argf)
{
    return rb_str_new2("ARGF");
}

Returns “ARGF”.

ARGF.to_write_io → io

io.c View on GitHub

          
            static VALUE
argf_write_io(VALUE argf)
{
    if (!RTEST(ARGF.current_file)) {
        rb_raise(rb_eIOError, "not opened for writing");
    }
    return GetWriteIO(ARGF.current_file);
}

Returns IO instance tied to ARGF for writing if inplace mode is enabled.

ARGF.write(string) → integer

io.c View on GitHub

          
            static VALUE
argf_write(VALUE argf, VALUE str)
{
    return rb_io_write(argf_write_io(argf), str);
}

Writes string if inplace mode.

ARGF

ARGF and ARGV

Reading

Simplest Case

About the Examples

Sources in ARGV

Filepaths in ARGV

Specifying $stdin in ARGV

Mixtures and Repetitions in ARGV

Modifications to ARGV

Empty ARGV

More Read Methods

About Enumerable

Writing

ARGF.argv → ARGV

ARGF.binmode → ARGF

ARGF.binmode? → true or false

ARGF.close → ARGF

ARGF.closed? → true or false

ARGF.each(sep=$/) {|line| block } → ARGF

ARGF.each(sep=$/, limit) {|line| block } → ARGF

ARGF.each(...) → an_enumerator

ARGF.each_byte {|byte| block } → ARGF

ARGF.each_byte → an_enumerator

ARGF.each_char {|char| block } → ARGF

ARGF.each_char → an_enumerator

ARGF.each_codepoint {|codepoint| block } → ARGF

ARGF.each_codepoint → an_enumerator

ARGF.each_line(sep=$/) {|line| block } → ARGF

ARGF.each_line(sep=$/, limit) {|line| block } → ARGF

ARGF.each_line(...) → an_enumerator

ARGF.eof → true or false

ARGF.eof? → true or false

ARGF.external_encoding → encoding

ARGF.file → IO or File object

ARGF.filename → String

ARGF.fileno → integer

ARGF.getbyte → Integer or nil

ARGF.getc → String or nil

ARGF.gets(sep=$/ [, getline_args]) → string or nil

ARGF.gets(limit [, getline_args]) → string or nil

ARGF.gets(sep, limit [, getline_args]) → string or nil

ARGF.inplace_mode → String

ARGF.inplace_mode = ext → ARGF

inspect

ARGF.internal_encoding → encoding

ARGF.lineno → integer

ARGF.lineno = integer → integer

ARGF.path → String

ARGF.pos → Integer

ARGF.pos = position → Integer

print(*objects) → nil

printf(format_string, *objects) → nil

putc(object) → object

puts(*objects) → nil

ARGF.read([length [, outbuf]]) → string, outbuf, or nil

ARGF.read_nonblock(maxlen[, options]) → string

ARGF.read_nonblock(maxlen, outbuf[, options]) → outbuf

ARGF.readbyte → Integer

ARGF.readchar → String or nil

ARGF.readline(sep=$/) → string

ARGF.readline(limit) → string

ARGF.readline(sep, limit) → string

ARGF.readlines(sep = $/, chomp: false) → array

ARGF.readlines(limit, chomp: false) → array

ARGF.readlines(sep, limit, chomp: false) → array

ARGF.readpartial(maxlen) → string

ARGF.readpartial(maxlen, outbuf) → outbuf

ARGF.rewind → 0

ARGF.seek(amount, whence=IO::SEEK_SET) → 0

ARGF.set_encoding(ext_enc) → ARGF

ARGF.set_encoding("ext_enc:int_enc") → ARGF

ARGF.set_encoding(ext_enc, int_enc) → ARGF

ARGF.set_encoding("ext_enc:int_enc", opt) → ARGF

ARGF.set_encoding(ext_enc, int_enc, opt) → ARGF

ARGF.skip → ARGF

ARGF.tell → Integer

ARGF.to_a(sep = $/, chomp: false) → array

ARGF.to_a(limit, chomp: false) → array

ARGF.to_a(sep, limit, chomp: false) → array

ARGF and `ARGV`

Sources in `ARGV`

Filepaths in `ARGV`

Specifying `$stdin` in `ARGV`

Mixtures and Repetitions in `ARGV`

Modifications to `ARGV`

Empty `ARGV`