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Class: ARGF

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, ::Enumerable
Inherits: Object
Defined in: io.c,
io.c

Overview

ARGF is a stream designed for use in scripts that process files given as command-line arguments or passed in via STDIN.

The arguments passed to your script are stored in the ARGV ::Array, one argument per element. ARGF assumes that any arguments that aren't filenames have been removed from ARGV. For example:

$ ruby argf.rb --verbose file1 file2

ARGV  #=> ["--verbose", "file1", "file2"]
option = ARGV.shift #=> "--verbose"
ARGV  #=> ["file1", "file2"]

You can now use ARGF to work with a concatenation of each of these named files. For instance, #read will return the contents of file1 followed by the contents of file2.

After a file in ARGV has been read ARGF removes it from the ::Array. Thus, after all files have been read ARGV will be empty.

You can manipulate ARGV yourself to control what ARGF operates on. If you remove a file from ARGV, it is ignored by ARGF; if you add files to ARGV, they are treated as if they were named on the command line. For example:

ARGV.replace ["file1"]
ARGF.readlines # Returns the contents of file1 as an Array
ARGV           #=> []
ARGV.replace ["file2", "file3"]
ARGF.read      # Returns the contents of file2 and file3

If ARGV is empty, ARGF acts as if it contained STDIN, i.e. the data piped to your script. For example:

$ echo "glark" | ruby -e 'p ARGF.read'
"glark\n"

Instance Attribute Summary

::Enumerable - Included

#all?

Passes each element of the collection to the given block.
#any?

Passes each element of the collection to the given block.
#none?

Passes each element of the collection to the given block.
#one?

Passes each element of the collection to the given block.

Instance Method Summary

::Enumerable - Included

#chunk

Enumerates over the items, chunking them together based on the return value of the block.
#collect

Alias for Enumerable#map.
#collect_concat

Alias for Enumerable#flat_map.
#count

Returns the number of items in enum through enumeration.
#cycle

Calls block for each element of enum repeatedly n times or forever if none or nil is given.
#detect

Alias for Enumerable#find.
#drop

Drops first n elements from enum, and returns rest elements in an array.
#drop_while

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.
#each_cons

Iterates the given block for each array of consecutive <n> elements.
#each_entry

Calls block once for each element in self, passing that element as a parameter, converting multiple values from yield to an array.
#each_slice

Iterates the given block for each slice of <n> elements.
#each_with_index

Calls block with two arguments, the item and its index, for each item in enum.
#each_with_object

Iterates the given block for each element with an arbitrary object given, and returns the initially given object.
#entries

Alias for Enumerable#to_a.
#find

Passes each entry in enum to block.
#find_all

Alias for Enumerable#select.
#find_index

Compares each entry in enum with value or passes to block.
#first

Returns the first element, or the first n elements, of the enumerable.
#flat_map

Returns a new array with the concatenated results of running block once for every element in enum.
#grep

Returns an array of every element in enum for which Pattern === element.
#group_by

Groups the collection by result of the block.
#include?

Alias for Enumerable#member?.
#inject

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.
#lazy

Returns a lazy enumerator, whose methods map/collect, flat_map/collect_concat, select/find_all, reject, grep, zip, take, take_while, drop, and drop_while enumerate values only on an as-needed basis.
#map

Returns a new array with the results of running block once for every element in enum.
#max

Returns the object in enum with the maximum value.
#max_by

Returns the object in enum that gives the maximum value from the given block.
#member?

Returns true if any member of enum equals obj.
#min

Returns the object in enum with the minimum value.
#min_by

Returns the object in enum that gives the minimum value from the given block.
#minmax

Returns two elements array which contains the minimum and the maximum value in the enumerable.
#minmax_by

Returns a two element array containing the objects in enum that correspond to the minimum and maximum values respectively from the given block.
#partition

Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.
#reduce

Alias for Enumerable#inject.
#reject

Returns an array for all elements of enum for which the given block returns false.
#reverse_each

Builds a temporary array and traverses that array in reverse order.
#select

Returns an array containing all elements of enum for which the given block returns a true value.
#slice_after

Creates an enumerator for each chunked elements.
#slice_before

Creates an enumerator for each chunked elements.
#slice_when

Creates an enumerator for each chunked elements.
#sort

Returns an array containing the items in enum sorted, either according to their own <=> method, or by using the results of the supplied block.
#sort_by

Sorts enum using a set of keys generated by mapping the values in enum through the given block.
#take

Returns first n elements from enum.
#take_while

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.
#to_a

Returns an array containing the items in enum.
#to_h

Returns the result of interpreting enum as a list of [key, value] pairs.
#zip

Takes one element from enum and merges corresponding elements from each args.

Instance Attribute Details

#binmode ⇒ ARGF (readonly)

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.

#binmode? ⇒ Boolean (readonly)

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

For example:

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

#closed? ⇒ Boolean (readonly)

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

#eof? ⇒ Boolean (readonly) #eof ⇒ Boolean
Also known as: #eof?

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

#eof? ⇒ Boolean (readonly) #eof ⇒ Boolean

Alias for #eof.

#inplace_mode ⇒ String (rw)

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

#inplace_mode=(ext) ⇒ ARGF (rw)

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.

#lineno ⇒ Integer (rw)

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

For example:

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

#lineno=(integer) ⇒ Integer (rw)

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 #lineno.

For example:

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

#tell ⇒ Integer (rw) #pos ⇒ Integer
Also known as: #tell

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

#pos=(position) ⇒ Integer (rw)

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

For example:

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

#tell ⇒ Integer (readonly) #pos ⇒ Integer

Alias for #pos.

Instance Method Details

#argv ⇒ 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"]

#bytes

This is a deprecated alias for #each_byte.

#chars

This is a deprecated alias for #each_char.

#close ⇒ ARGF

Closes the current file and skips to the next in the stream. Trying to close a file that has already been closed causes an ::IOError to be raised.

For example:

$ ruby argf.rb foo bar

ARGF.filename  #=> "foo"
ARGF.close
ARGF.filename  #=> "bar"
ARGF.close
ARGF.close     #=> closed stream (IOError)

#codepoints

This is a deprecated alias for #each_codepoint.

#each(sep = $/) {|line| ... } ⇒ ARGF #each(sep = $/, limit) {|line| ... } ⇒ ARGF #each(...) ⇒ Enumerator
Also known as: #each_line

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

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

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 a ::Fixnum 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 #filename and #lineno methods can be used to determine the filename and line number, respectively, of the current line.

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.lineno == 1
  puts "#{ARGF.lineno}: #{line}"
end

#bytes {|byte| ... } ⇒ ARGF #bytes ⇒ Enumerator

ARGF.each_byte {|byte| block } -> ARGF

ARGF.each_byte                  -> an_enumerator

Iterates over each byte of each file in ARGV. A byte is returned as a ::Fixnum 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 #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]

#each_char {|char| ... } ⇒ ARGF #each_char ⇒ Enumerator

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 #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.

#each_codepoint {|codepoint| ... } ⇒ ARGF #each_codepoint ⇒ Enumerator

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 #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.

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

Alias for #each.

#external_encoding ⇒ 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 #internal_encoding, which is the encoding used to represent this text within Ruby.

To set the external encoding use #set_encoding.

For example:

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

#file ⇒ IO, File object

Returns the current file as an ::IO or ::File object. #<IO:<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>

#filename ⇒ String #path ⇒ String

Alias for #path.

#fileno ⇒ Fixnum #to_i ⇒ Fixnum

Alias for #to_i.

#getbyte ⇒ Fixnum?

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

#getc ⇒ String?

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

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

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.

#to_s ⇒ String #inspect ⇒ String

Alias for #to_s.

#internal_encoding ⇒ Encoding

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

If #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.

#lines(*args)

This is a deprecated alias for #each_line.

#filename ⇒ String #path ⇒ String
Also known as: #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"

#printf(format_string [, obj, ...]) ⇒ nil

Alias for IO#printf.

#putc(obj) ⇒ Object

Alias for IO#putc.

#puts(obj, ...) ⇒ nil

Alias for IO#puts.

#read([length [, outbuf]]) ⇒ String, ...

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 #readpartial or #read_nonblock.

#read_nonblock(maxlen) ⇒ String #read_nonblock(maxlen, outbuf) ⇒ outbuf

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

#readbyte ⇒ Fixnum

Reads the next 8-bit byte from ARGF and returns it as a ::Fixnum. 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)

#readchar ⇒ String?

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)

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

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.

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

Alias for #to_a.

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

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. #readpartial returns empty strings for EOFs except the last one and raises ::EOFError for the last one.

#rewind ⇒ 0

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

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

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

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

#set_encoding(ext_enc) ⇒ ARGF #set_encoding("ext_enc:int_enc") ⇒ ARGF #set_encoding(ext_enc, int_enc) ⇒ ARGF #set_encoding("ext_enc:int_enc", opt) ⇒ ARGF #set_encoding(ext_enc, int_enc, opt) ⇒ 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.

#skip ⇒ 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"

#readlines(sep = $/) ⇒ Array #readlines(limit) ⇒ Array #readlines(sep, limit) ⇒ Array
Also known as: #readlines

ARGF.to_a(sep=$/) -> array

ARGF.to_a(limit)      -> array
ARGF.to_a(sep, limit) -> array

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"

#fileno ⇒ Fixnum #to_i ⇒ Fixnum
Also known as: #fileno

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

#to_io ⇒ IO

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>>

#to_s ⇒ String Also known as: #inspect

Returns “ARGF”.

#to_write_io ⇒ IO

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

#write(string) ⇒ Integer

Writes string if inplace mode.