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Python Source  |  1999-04-16  |  4.1 KB  |  120 lines
  1. #!/usr/bin/python
  2. # Module and documentation by Eric S. Raymond, 21 Dec 1998 
  3.  
  4. import sys, os, string
  5.  
  6. class shlex:
  7.     "A lexical analyzer class for simple shell-like syntaxes." 
  8.     def __init__(self, instream=None):
  9.         if instream:
  10.             self.instream = instream
  11.         else:
  12.             self.instream = sys.stdin
  13.         self.commenters = '#'
  14.         self.wordchars = 'abcdfeghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
  15.         self.whitespace = ' \t\r\n'
  16.         self.quotes = '\'"'
  17.         self.state = ' '
  18.         self.pushback = [];
  19.         self.lineno = 1
  20.         self.debug = 0
  21.         self.token = ''
  22.  
  23.     def push_token(self, tok):
  24.         "Push a token onto the stack popped by the get_token method"
  25.         if (self.debug >= 1):
  26.             print "Pushing " + tok
  27.         self.pushback = [tok] + self.pushback;
  28.  
  29.     def get_token(self):
  30.         "Get a token from the input stream (or from stack if it's monempty)"
  31.         if self.pushback:
  32.             tok = self.pushback[0]
  33.             self.pushback = self.pushback[1:]
  34.             if (self.debug >= 1):
  35.                 print "Popping " + tok
  36.             return tok
  37.         tok = ''
  38.         while 1:
  39.             nextchar = self.instream.read(1);
  40.             if nextchar == '\n':
  41.                 self.lineno = self.lineno + 1
  42.             if self.debug >= 3:
  43.                 print "In state " + repr(self.state) + " I see character: " + repr(nextchar) 
  44.             if self.state == None:
  45.                 return ''
  46.             elif self.state == ' ':
  47.                 if not nextchar:
  48.                     self.state = None;    # end of file
  49.                     break
  50.                 elif nextchar in self.whitespace:
  51.                     if self.debug >= 2:
  52.                         print "I see whitespace in whitespace state"
  53.                     if self.token:
  54.                         break    # emit current token
  55.                     else:
  56.                         continue
  57.                 elif nextchar in self.commenters:
  58.                     self.instream.readline()
  59.                     self.lineno = self.lineno + 1
  60.                 elif nextchar in self.wordchars:
  61.                     self.token = nextchar
  62.                     self.state = 'a'
  63.                 elif nextchar in self.quotes:
  64.                     self.token = nextchar
  65.                     self.state = nextchar
  66.                 else:
  67.                     self.token = nextchar
  68.                     if self.token:
  69.                         break    # emit current token
  70.                     else:
  71.                         continue
  72.             elif self.state in self.quotes:
  73.                 self.token = self.token + nextchar
  74.                 if nextchar == self.state:
  75.                     self.state = ' '
  76.                     break
  77.             elif self.state == 'a':
  78.                 if not nextchar:
  79.                     self.state = None;    # end of file
  80.                     break
  81.                 elif nextchar in self.whitespace:
  82.                     if self.debug >= 2:
  83.                         print "I see whitespace in word state"
  84.                     self.state = ' '
  85.                     if self.token:
  86.                         break    # emit current token
  87.                     else:
  88.                         continue
  89.                 elif nextchar in self.commenters:
  90.                     self.instream.readline()
  91.                     self.lineno = self.lineno + 1
  92.                 elif nextchar in self.wordchars or nextchar in self.quotes:
  93.                     self.token = self.token + nextchar
  94.                 else:
  95.                     self.pushback = [nextchar] + self.pushback
  96.                     if self.debug >= 2:
  97.                         print "I see punctuation in word state"
  98.                     state = ' '
  99.                     if self.token:
  100.                         break    # emit current token
  101.                     else:
  102.                         continue
  103.                 
  104.         result = self.token
  105.         self.token = ''
  106.         if self.debug >= 1:
  107.             print "Token: " + result
  108.         return result
  109.  
  110. if __name__ == '__main__': 
  111.  
  112.     lexer = shlex()
  113.     while 1:
  114.         tt = lexer.get_token()
  115.         if tt != None:
  116.             print "Token: " + repr(tt)
  117.         else:
  118.             break
  119.  
  120.