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Shellwords

Manipulates strings like the UNIX Bourne shell

This module manipulates strings according to the word parsing rules of the UNIX Bourne shell.

The shellwords() function was originally a port of shellwords.pl, but modified to conform to POSIX / SUSv3 (IEEE Std 1003.1-2001 [1]).

Usage

You can use shellwords to parse a string into a Bourne shell friendly Array.

require 'shellwords'

argv = Shellwords.split('three blind "mice"')
argv #=> ["three", "blind", "mice"]

Once you’ve required Shellwords, you can use the split alias String#shellsplit.

argv = "see how they run".shellsplit
argv #=> ["see", "how", "they", "run"]

Be careful you don’t leave a quote unmatched.

argv = "they all ran after the farmer's wife".shellsplit
     #=> ArgumentError: Unmatched double quote: ...

In this case, you might want to use ::escape, or it’s alias String#shellescape.

This method will escape the String for you to safely use with a Bourne shell.

argv = Shellwords.escape("special's.txt")
argv #=> "special\\'s.txt"
system("cat " + argv)

Shellwords also comes with a core extension for Array, Array#shelljoin.

argv = %w{ls -lta lib}
system(argv.shelljoin)

You can use this method to create an escaped string out of an array of tokens separated by a space. In this example we’ll use the literal shortcut for Array.new.

Authors

  • Wakou Aoyama

  • Akinori MUSHA <knu@iDaemons.org>

Contact

  • Akinori MUSHA <knu@iDaemons.org> (current maintainer)

Resources

1: IEEE Std 1003.1-2004

Public Class Methods

escape(str) click to toggle source
Alias for: shellescape
join(array) click to toggle source
Alias for: shelljoin
shellescape(str) click to toggle source

Escapes a string so that it can be safely used in a Bourne shell command line. str can be a non-string object that responds to to_s.

Note that a resulted string should be used unquoted and is not intended for use in double quotes nor in single quotes.

argv = Shellwords.escape("It's better to give than to receive")
argv #=> "It\\'s\\ better\\ to\\ give\\ than\\ to\\ receive"

String#shellescape is a shorthand for this function.

argv = "It's better to give than to receive".shellescape
argv #=> "It\\'s\\ better\\ to\\ give\\ than\\ to\\ receive"

# Search files in lib for method definitions
pattern = "^[ \t]*def "
open("| grep -Ern #{pattern.shellescape} lib") { |grep|
  grep.each_line { |line|
    file, lineno, matched_line = line.split(':', 3)
    # ...
  }
}

It is the caller’s responsibility to encode the string in the right encoding for the shell environment where this string is used.

Multibyte characters are treated as multibyte characters, not bytes.

Returns an empty quoted String if str has a length of zero.

 
               # File shellwords.rb, line 123
def shellescape(str)
  str = str.to_s

  # An empty argument will be skipped, so return empty quotes.
  return "''" if str.empty?

  str = str.dup

  # Treat multibyte characters as is.  It is caller's responsibility
  # to encode the string in the right encoding for the shell
  # environment.
  str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/, "\\\\\\1")

  # A LF cannot be escaped with a backslash because a backslash + LF
  # combo is regarded as line continuation and simply ignored.
  str.gsub!(/\n/, "'\n'")

  return str
end
            
Also aliased as: escape
shelljoin(array) click to toggle source

Builds a command line string from an argument list, array.

All elements are joined into a single string with fields separated by a space, where each element is escaped for Bourne shell and stringified using to_s.

ary = ["There's", "a", "time", "and", "place", "for", "everything"]
argv = Shellwords.join(ary)
argv #=> "There\\'s a time and place for everything"

Array#shelljoin is a shortcut for this function.

ary = ["Don't", "rock", "the", "boat"]
argv = ary.shelljoin
argv #=> "Don\\'t rock the boat"

You can also mix non-string objects in the elements as allowed in Array#join.

output = `#{['ps', '-p', $$].shelljoin}`
 
               # File shellwords.rb, line 169
def shelljoin(array)
  array.map { |arg| shellescape(arg) }.join(' ')
end
            
Also aliased as: join
shellsplit(line) click to toggle source

Splits a string into an array of tokens in the same way the UNIX Bourne shell does.

argv = Shellwords.split('here are "two words"')
argv #=> ["here", "are", "two words"]

String#shellsplit is a shortcut for this function.

argv = 'here are "two words"'.shellsplit
argv #=> ["here", "are", "two words"]
 
               # File shellwords.rb, line 70
def shellsplit(line)
  words = []
  field = ''
  line.scan(/\G\s*(?>([^\s\\\"]+)|'([^\]*)'|"((?:[^\"\]|\.)*)"|(\.?)|(\S))(\s|\z)?/m) do
    |word, sq, dq, esc, garbage, sep|
    raise ArgumentError, "Unmatched double quote: #{line.inspect}" if garbage
    field << (word || sq || (dq || esc).gsub(/\(.)/, '\1'))
    if sep
      words << field
      field = ''
    end
  end
  words
end
            
Also aliased as: shellwords, split
shellwords(line) click to toggle source
Alias for: shellsplit
split(line) click to toggle source
Alias for: shellsplit

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