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56 lines
1.4 KiB
Python
56 lines
1.4 KiB
Python
#
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# Variable substitution. Variables are $delimited$
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#
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import re
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error = 'varsubst.error'
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class Varsubst:
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def __init__(self, dict):
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self.dict = dict
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self.prog = re.compile('\$([a-zA-Z0-9_]*)\$')
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self.do_useindent = 0
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def useindent(self, onoff):
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self.do_useindent = onoff
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def subst(self, s):
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rv = ''
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while 1:
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m = self.prog.search(s)
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if not m:
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return rv + s
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rv = rv + s[:m.start()]
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s = s[m.end():]
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if m.end() - m.start() == 2:
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# Escaped dollar
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rv = rv + '$'
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s = s[2:]
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continue
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name = m.group(1)
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if not self.dict.has_key(name):
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raise error('No such variable: '+name)
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value = self.dict[name]
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if self.do_useindent and '\n' in value:
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value = self._modindent(value, rv)
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rv = rv + value
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def _modindent(self, value, old):
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lastnl = old.rfind('\n', 0) + 1
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lastnl = len(old) - lastnl
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sub = '\n' + (' '*lastnl)
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return re.sub('\n', sub, value)
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def _test():
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import sys
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import os
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sys.stderr.write('-- Copying stdin to stdout with environment map --\n')
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c = Varsubst(os.environ)
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c.useindent(1)
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d = sys.stdin.read()
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sys.stdout.write(c.subst(d))
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sys.exit(1)
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if __name__ == '__main__':
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_test()
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