class ARGF

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"]

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

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.

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;
}

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

static VALUE
argf_binmode_p(VALUE argf)
{
    return ARGF.binmode ? Qtrue : Qfalse;
}

This is a deprecated alias for each_byte.

static VALUE
argf_bytes(VALUE argf)
{
    rb_warn_deprecated("ARGF#bytes", "#each_byte");
    if (!rb_block_given_p())
        return rb_enumeratorize(argf, ID2SYM(rb_intern("each_byte")), 0, 0);
    return argf_each_byte(argf);
}

This is a deprecated alias for each_char.

static VALUE
argf_chars(VALUE argf)
{
    rb_warn_deprecated("ARGF#chars", "#each_char");
    if (!rb_block_given_p())
        return rb_enumeratorize(argf, ID2SYM(rb_intern("each_char")), 0, 0);
    return argf_each_char(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

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;
}

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

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

This is a deprecated alias for each_codepoint.

static VALUE
argf_codepoints(VALUE argf)
{
    rb_warn_deprecated("ARGF#codepoints", "#each_codepoint");
    if (!rb_block_given_p())
        return rb_enumeratorize(argf, ID2SYM(rb_intern("each_codepoint")), 0, 0);
    return argf_each_codepoint(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

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;
}

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]

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 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.

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 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.

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;
}

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

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 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>

static VALUE
argf_external_encoding(VALUE argf)
{
    if (!RTEST(ARGF.current_file)) {
        return rb_enc_from_encoding(rb_default_external_encoding());
    }
    return rb_io_external_encoding(rb_io_check_io(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>

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

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"

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

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

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);
}

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

static VALUE
argf_getbyte(VALUE argf)
{
    VALUE ch;

  retry:
    if (!next_argv()) return Qnil;
    if (!RB_TYPE_P(ARGF.current_file, T_FILE)) {
        ch = rb_funcall3(ARGF.current_file, 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;
}

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

static VALUE
argf_getc(VALUE argf)
{
    VALUE ch;

  retry:
    if (!next_argv()) return Qnil;
    if (ARGF_GENERIC_INPUT_P()) {
        ch = rb_funcall3(ARGF.current_file, 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;
}

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.

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 file extension appended to the names 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.

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);
}

Sets the filename extension for in-place editing mode to the given String. Each file being edited has this value appended to its filename. The modified file is saved under this new name.

For example:

$ ruby argf.rb file.txt

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

Each line of file.txt has the first occurrence of “foo” replaced with “bar”, then the new line is written out to file.txt.bak.

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;
}

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.

static VALUE
argf_internal_encoding(VALUE argf)
{
    if (!RTEST(ARGF.current_file)) {
        return rb_enc_from_encoding(rb_default_external_encoding());
    }
    return rb_io_internal_encoding(rb_io_check_io(ARGF.current_file));
}

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

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

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

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

This is a deprecated alias for each_line.

static VALUE
argf_lines(int argc, VALUE *argv, VALUE argf)
{
    rb_warn_deprecated("ARGF#lines", "#each_line");
    if (!rb_block_given_p())
        return rb_enumeratorize(argf, ID2SYM(rb_intern("each_line")), argc, argv);
    return argf_each_line(argc, argv, argf);
}

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

For example:

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

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);
}

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

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

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

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

produces:

This is 100 percent.

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

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

    return Qnil;
}

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

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

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

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

produces:

AA

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

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

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

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

produces:

this
is
a
test

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

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

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

    return Qnil;
}

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.

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) {
            len -= slen;
            argv[0] = INT2NUM(len);
            goto retry;
        }
    }
    return str;
}

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

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 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)

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 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)

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 = rb_funcall3(ARGF.current_file, 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;
}

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.

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;
}

Reads ARGF‘s current file in its entirety, returning an Array of its lines, one line per element. Lines are assumed to be separated by sep.

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

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 = rb_funcall3(ARGF.current_file, 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 at most maxlen bytes from the ARGF stream.

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 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.

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

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"

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;
}

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

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);
}

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.

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;
}

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"

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

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_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 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>>

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

Returns “ARGF”.

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

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

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);
}

Writes string if inplace mode.

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