Doc/lib/libgetopt.tex

   1 \section{\module{getopt} ---
   2          Parser for command line options}
   3
   4 \declaremodule{standard}{getopt}
   5 \modulesynopsis{Portable parser for command line options; support both
   6                 short and long option names.}
   7
   8
   9 This module helps scripts to parse the command line arguments in
  10 \code{sys.argv}.
  11 It supports the same conventions as the \UNIX{} \cfunction{getopt()}
  12 function (including the special meanings of arguments of the form
  13 `\code{-}' and `\code{-}\code{-}').
  14 % That's to fool latex2html into leaving the two hyphens alone!
  15 Long options similar to those supported by
  16 GNU software may be used as well via an optional third argument.
  17 This module provides a single function and an exception:
  18
  19 \begin{funcdesc}{getopt}{args, options\optional{, long_options}}
  20 Parses command line options and parameter list.  \var{args} is the
  21 argument list to be parsed, without the leading reference to the
  22 running program. Typically, this means \samp{sys.argv[1:]}.
  23 \var{options} is the string of option letters that the script wants to
  24 recognize, with options that require an argument followed by a colon
  25 (\character{:}; i.e., the same format that \UNIX{}
  26 \cfunction{getopt()} uses).
  27
  28 \note{Unlike GNU \cfunction{getopt()}, after a non-option
  29 argument, all further arguments are considered also non-options.
  30 This is similar to the way non-GNU \UNIX{} systems work.}
  31
  32 \var{long_options}, if specified, must be a list of strings with the
  33 names of the long options which should be supported.  The leading
  34 \code{'-}\code{-'} characters should not be included in the option
  35 name.  Long options which require an argument should be followed by an
  36 equal sign (\character{=}).  To accept only long options,
  37 \var{options} should be an empty string.  Long options on the command
  38 line can be recognized so long as they provide a prefix of the option
  39 name that matches exactly one of the accepted options.  For example,
  40 if \var{long_options} is \code{['foo', 'frob']}, the option
  41 \longprogramopt{fo} will match as \longprogramopt{foo}, but
  42 \longprogramopt{f} will not match uniquely, so \exception{GetoptError}
  43 will be raised.
  44
  45 The return value consists of two elements: the first is a list of
  46 \code{(\var{option}, \var{value})} pairs; the second is the list of
  47 program arguments left after the option list was stripped (this is a
  48 trailing slice of \var{args}).  Each option-and-value pair returned
  49 has the option as its first element, prefixed with a hyphen for short
  50 options (e.g., \code{'-x'}) or two hyphens for long options (e.g.,
  51 \code{'-}\code{-long-option'}), and the option argument as its second
  52 element, or an empty string if the option has no argument.  The
  53 options occur in the list in the same order in which they were found,
  54 thus allowing multiple occurrences.  Long and short options may be
  55 mixed.
  56 \end{funcdesc}
  57
  58 \begin{funcdesc}{gnu_getopt}{args, options\optional{, long_options}}
  59 This function works like \function{getopt()}, except that GNU style
  60 scanning mode is used by default. This means that option and
  61 non-option arguments may be intermixed. The \function{getopt()}
  62 function stops processing options as soon as a non-option argument is
  63 encountered.
  64
  65 If the first character of the option string is `+', or if the
  66 environment variable POSIXLY_CORRECT is set, then option processing
  67 stops as soon as a non-option argument is encountered.
  68 \end{funcdesc}
  69
  70 \begin{excdesc}{GetoptError}
  71 This is raised when an unrecognized option is found in the argument
  72 list or when an option requiring an argument is given none.
  73 The argument to the exception is a string indicating the cause of the
  74 error.  For long options, an argument given to an option which does
  75 not require one will also cause this exception to be raised.  The
  76 attributes \member{msg} and \member{opt} give the error message and
  77 related option; if there is no specific option to which the exception
  78 relates, \member{opt} is an empty string.
  79
  80 \versionchanged[Introduced \exception{GetoptError} as a synonym for
  81                 \exception{error}]{1.6}
  82 \end{excdesc}
  83
  84 \begin{excdesc}{error}
  85 Alias for \exception{GetoptError}; for backward compatibility.
  86 \end{excdesc}
  87
  88
  89 An example using only \UNIX{} style options:
  90
  91 \begin{verbatim}
  92 >>> import getopt
  93 >>> args = '-a -b -cfoo -d bar a1 a2'.split()
  94 >>> args
  95 ['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2']
  96 >>> optlist, args = getopt.getopt(args, 'abc:d:')
  97 >>> optlist
  98 [('-a', ''), ('-b', ''), ('-c', 'foo'), ('-d', 'bar')]
  99 >>> args
 100 ['a1', 'a2']
 101 \end{verbatim}
 102
 103 Using long option names is equally easy:
 104
 105 \begin{verbatim}
 106 >>> s = '--condition=foo --testing --output-file abc.def -x a1 a2'
 107 >>> args = s.split()
 108 >>> args
 109 ['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2']
 110 >>> optlist, args = getopt.getopt(args, 'x', [
 111 ...     'condition=', 'output-file=', 'testing'])
 112 >>> optlist
 113 [('--condition', 'foo'), ('--testing', ''), ('--output-file', 'abc.def'), ('-x',
 114  '')]
 115 >>> args
 116 ['a1', 'a2']
 117 \end{verbatim}
 118
 119 In a script, typical usage is something like this:
 120
 121 \begin{verbatim}
 122 import getopt, sys
 123
 124 def main():
 125     try:
 126         opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
 127     except getopt.GetoptError:
 128         # print help information and exit:
 129         usage()
 130         sys.exit(2)
 131     output = None
 132     verbose = False
 133     for o, a in opts:
 134         if o == "-v":
 135             verbose = True
 136         if o in ("-h", "--help"):
 137             usage()
 138             sys.exit()
 139         if o in ("-o", "--output"):
 140             output = a
 141     # ...
 142
 143 if __name__ == "__main__":
 144     main()
 145 \end{verbatim}
 146
 147 \begin{seealso}
 148   \seemodule{optparse}{More object-oriented command line option parsing.}
 149 \end{seealso}