1 #

     2 # Variable substitution. Variables are $delimited$

     3 #

     4 import re

     5 

     6 error = 'varsubst.error'

     7 

     8 class Varsubst:

     9     def __init__(self, dict):

    10         self.dict = dict

    11         self.prog = re.compile('\$([a-zA-Z0-9_]*)\$')

    12         self.do_useindent = 0

    13 

    14     def useindent(self, onoff):

    15         self.do_useindent = onoff

    16 

    17     def subst(self, s):

    18         rv = ''

    19         while 1:

    20             m = self.prog.search(s)

    21             if not m:

    22                 return rv + s

    23             rv = rv + s[:m.start()]

    24             s = s[m.end():]

    25             if m.end() - m.start() == 2:

    26                 # Escaped dollar

    27                 rv = rv + '$'

    28                 s = s[2:]

    29                 continue

    30             name = m.group(1)

    31             if not self.dict.has_key(name):

    32                 raise error, 'No such variable: '+name

    33             value = self.dict[name]

    34             if self.do_useindent and '\n' in value:

    35                 value = self._modindent(value, rv)

    36             rv = rv + value

    37 

    38     def _modindent(self, value, old):

    39         lastnl = old.rfind('\n', 0) + 1

    40         lastnl = len(old) - lastnl

    41         sub = '\n' + (' '*lastnl)

    42         return re.sub('\n', sub, value)

    43 

    44 def _test():

    45     import sys

    46     import os

    47 

    48     sys.stderr.write('-- Copying stdin to stdout with environment map --\n')

    49     c = Varsubst(os.environ)

    50     c.useindent(1)

    51     d = sys.stdin.read()

    52     sys.stdout.write(c.subst(d))

    53     sys.exit(1)

    54 

    55 if __name__ == '__main__':

    56     _test()