# module 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 the Shell & Utilities volume of the IEEE Std 1003.1-2008, 2016 Edition [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"]

They treat quotes as special characters, so an unmatched quote will cause an `ArgumentError`.

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

`Shellwords` also provides methods that do the opposite. `Shellwords.escape`, or its alias, `String#shellescape`, escapes shell metacharacters in a string for use in a command line.

    filename = "special's.txt"

    system("cat -- #{filename.shellescape}")
    # runs "cat -- special\\'s.txt"

Note the ‘–’. Without it, cat(1) will treat the following argument as a command line option if it starts with ‘-’. It is guaranteed that `Shellwords.escape` converts a string to a form that a Bourne shell will parse back to the original string, but it is the programmer’s responsibility to make sure that passing an arbitrary argument to a command does no harm.

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

    dir = "Funny GIFs"
    argv = %W[ls -lta -- #{dir}]
    system(argv.shelljoin + " | less")
    # runs "ls -lta -- Funny\\ GIFs | less"

You can use this method to build a complete command line out of an array of arguments.

### Authors¶ ↑

- Wakou Aoyama

- Akinori MUSHA <knu@iDaemons.org>

### Contact¶ ↑

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

### Resources¶ ↑

1: IEEE Std 1003.1-2008, 2016 Edition, the Shell & Utilities volume

### Public Class Methods

escape(str)
Alias for: shellescape
join(array)
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 -e #{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 as bytes.

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

    # File lib/shellwords.rb, line 148
    def shellescape(str)
      str = str.to_s

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

      str = str.dup

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

      # A LF cannot be escaped with a backslash because a backslash + LF
      # combo is regarded as a 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 the 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 lib/shellwords.rb, line 194
    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"]

Note, however, that this is not a command line parser. Shell metacharacters except for the single and double quotes and backslash are not treated as such.

    argv = Shellwords.split('ruby my_prog.rb | less')
    argv #=> ["ruby", "my_prog.rb", "|", "less"]

`String#shellsplit` is a shortcut for this function.

    argv = 'here are "two words"'.shellsplit
    argv #=> ["here", "are", "two words"]

    # File lib/shellwords.rb, line 88
    def shellsplit(line)
      words = []
      field = String.new
      line.scan(/\G\s*(?>([^\s\\\'\"]+)|'([^\']*)'|"((?:[^\"\\]|\\.)*)"|(\\.?)|(\S))(\s|\z)?/m) do
        |word, sq, dq, esc, garbage, sep|
        raise ArgumentError, "Unmatched quote: #{line.inspect}" if garbage
        # 2.2.3 Double-Quotes:
        #
        #   The <backslash> shall retain its special meaning as an
        #   escape character only when followed by one of the following
        #   characters when considered special:
        #
        #   $ ` " \ <newline>
        field << (word || sq || (dq && dq.gsub(/\\([$`"\\\n])/, '\\1')) || esc.gsub(/\\(.)/, '\\1'))
        if sep
          words << field
          field = String.new
        end
      end
      words
    end

Also aliased as: shellwords, split
shellwords(line)
Alias for: shellsplit
split(line)
Alias for: shellsplit

### Private Instance Methods

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 -e #{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 as bytes.

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

    # File lib/shellwords.rb, line 148
    def shellescape(str)
      str = str.to_s

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

      str = str.dup

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

      # A LF cannot be escaped with a backslash because a backslash + LF
      # combo is regarded as a 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 the 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 lib/shellwords.rb, line 194
    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"]

Note, however, that this is not a command line parser. Shell metacharacters except for the single and double quotes and backslash are not treated as such.

    argv = Shellwords.split('ruby my_prog.rb | less')
    argv #=> ["ruby", "my_prog.rb", "|", "less"]

`String#shellsplit` is a shortcut for this function.

    argv = 'here are "two words"'.shellsplit
    argv #=> ["here", "are", "two words"]

    # File lib/shellwords.rb, line 88
    def shellsplit(line)
      words = []
      field = String.new
      line.scan(/\G\s*(?>([^\s\\\'\"]+)|'([^\']*)'|"((?:[^\"\\]|\\.)*)"|(\\.?)|(\S))(\s|\z)?/m) do
        |word, sq, dq, esc, garbage, sep|
        raise ArgumentError, "Unmatched quote: #{line.inspect}" if garbage
        # 2.2.3 Double-Quotes:
        #
        #   The <backslash> shall retain its special meaning as an
        #   escape character only when followed by one of the following
        #   characters when considered special:
        #
        #   $ ` " \ <newline>
        field << (word || sq || (dq && dq.gsub(/\\([$`"\\\n])/, '\\1')) || esc.gsub(/\\(.)/, '\\1'))
        if sep
          words << field
          field = String.new
        end
      end
      words
    end

Also aliased as: shellwords, split
shellwords(line)
Alias for: shellsplit