cpython/Lib/getopt.py

# module getopt -- Standard command line processing.

# Function getopt.getopt() has a different interface but provides the
# similar functionality to the Unix getopt() function, with the
# addition of long-option support.  (Long option support added by Lars
# Wirzenius <liw@iki.fi>.)

# It has two required arguments: the first should be argv[1:] (it
# doesn't want the script name), the second the string of option
# letters as passed to Unix getopt() (i.e., a string of allowable
# option letters, with options requiring an argument followed by a
# colon).

# The optional third argument, if present, getopt.getopt works similar
# to the GNU getopt_long function (but optional arguments are not
# supported).  The third argument should be a list of strings that
# name the long options.  If the name ends '=', the argument requires
# an argument.

# It raises the exception getopt.error with a string argument if it
# detects an error.

# It returns two values:
# (1)	a list of pairs (option, option_argument) giving the options in
#	the order in which they were specified.  (I'd use a dictionary
#	but applications may depend on option order or multiple
#	occurrences.)  Boolean options have '' as option_argument.
# (2)	the list of remaining arguments (may be empty).

import string

error = 'getopt.error'

def getopt(args, shortopts, longopts = []):
    list = []
    longopts = longopts[:]
    longopts.sort()
    while args and args[0][:1] == '-' and args[0] != '-':
	if args[0] == '--':
	    args = args[1:]
	    break
	if args[0][:2] == '--':
	    list, args = do_longs(list, args[0][2:], longopts, args[1:])
	else:
	    list, args = do_shorts(list, args[0][1:], shortopts, args[1:])

    return list, args

def do_longs(list, opt, longopts, args):
    try:
	i = string.index(opt, '=')
	opt, optarg = opt[:i], opt[i+1:]
    except ValueError:
	optarg = None

    has_arg, opt = long_has_args(opt, longopts)
    if has_arg:
	if optarg is None:
	    if not args:
		raise error, 'option --%s requires argument' % opt
	    optarg, args = args[0], args[1:]
    elif optarg:
	raise error, 'option --%s must not have an argument' % opt
    list.append(('--' + opt, optarg or ''))
    return list, args

# Return:
#   has_arg?
#   full option name
def long_has_args(opt, longopts):
    optlen = len(opt)
    for i in range(len(longopts)):
	x, y = longopts[i][:optlen], longopts[i][optlen:]
	if opt != x:
	    continue
	if y != '' and y != '=' and i+1 < len(longopts):
	    if opt == longopts[i+1][:optlen]:
		raise error, 'option --%s not a unique prefix' % opt
	if longopts[i][-1:] in ('=', ):
	    return 1, longopts[i][:-1]
	return 0, longopts[i]
    raise error, 'option --' + opt + ' not recognized'

def do_shorts(list, optstring, shortopts, args):
    while optstring != '':
	opt, optstring = optstring[0], optstring[1:]
	if short_has_arg(opt, shortopts):
	    if optstring == '':
		if not args:
		    raise error, 'option -%s requires argument' % opt
		optstring, args = args[0], args[1:]
	    optarg, optstring = optstring, ''
	else:
	    optarg = ''
	list.append(('-' + opt, optarg))
    return list, args

def short_has_arg(opt, shortopts):
    for i in range(len(shortopts)):
	if opt == shortopts[i] != ':':
	    return shortopts[i+1:i+2] == ':'
    raise error, 'option -%s not recognized' % opt

if __name__ == '__main__':
    import sys
    print getopt(sys.argv[1:], "a:b", ["alpha=", "beta"])