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Text File  |  2000-12-21  |  4KB  |  121 lines
  1. """A lexical analyzer class for simple shell-like syntaxes."""
  2.  
  3. # Module and documentation by Eric S. Raymond, 21 Dec 1998 
  4.  
  5. import sys
  6.  
  7. class shlex:
  8.     "A lexical analyzer class for simple shell-like syntaxes." 
  9.     def __init__(self, instream=None):
  10.         if instream:
  11.             self.instream = instream
  12.         else:
  13.             self.instream = sys.stdin
  14.         self.commenters = '#'
  15.         self.wordchars = 'abcdfeghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
  16.         self.whitespace = ' \t\r\n'
  17.         self.quotes = '\'"'
  18.         self.state = ' '
  19.         self.pushback = [];
  20.         self.lineno = 1
  21.         self.debug = 0
  22.         self.token = ''
  23.  
  24.     def push_token(self, tok):
  25.         "Push a token onto the stack popped by the get_token method"
  26.         if (self.debug >= 1):
  27.             print "Pushing " + tok
  28.         self.pushback = [tok] + self.pushback;
  29.  
  30.     def get_token(self):
  31.         "Get a token from the input stream (or from stack if it's monempty)"
  32.         if self.pushback:
  33.             tok = self.pushback[0]
  34.             self.pushback = self.pushback[1:]
  35.             if (self.debug >= 1):
  36.                 print "Popping " + tok
  37.             return tok
  38.         tok = ''
  39.         while 1:
  40.             nextchar = self.instream.read(1);
  41.             if nextchar == '\n':
  42.                 self.lineno = self.lineno + 1
  43.             if self.debug >= 3:
  44.                 print "In state " + repr(self.state) + " I see character: " + repr(nextchar) 
  45.             if self.state == None:
  46.                 return ''
  47.             elif self.state == ' ':
  48.                 if not nextchar:
  49.                     self.state = None;    # end of file
  50.                     break
  51.                 elif nextchar in self.whitespace:
  52.                     if self.debug >= 2:
  53.                         print "I see whitespace in whitespace state"
  54.                     if self.token:
  55.                         break    # emit current token
  56.                     else:
  57.                         continue
  58.                 elif nextchar in self.commenters:
  59.                     self.instream.readline()
  60.                     self.lineno = self.lineno + 1
  61.                 elif nextchar in self.wordchars:
  62.                     self.token = nextchar
  63.                     self.state = 'a'
  64.                 elif nextchar in self.quotes:
  65.                     self.token = nextchar
  66.                     self.state = nextchar
  67.                 else:
  68.                     self.token = nextchar
  69.                     if self.token:
  70.                         break    # emit current token
  71.                     else:
  72.                         continue
  73.             elif self.state in self.quotes:
  74.                 self.token = self.token + nextchar
  75.                 if nextchar == self.state:
  76.                     self.state = ' '
  77.                     break
  78.             elif self.state == 'a':
  79.                 if not nextchar:
  80.                     self.state = None;    # end of file
  81.                     break
  82.                 elif nextchar in self.whitespace:
  83.                     if self.debug >= 2:
  84.                         print "I see whitespace in word state"
  85.                     self.state = ' '
  86.                     if self.token:
  87.                         break    # emit current token
  88.                     else:
  89.                         continue
  90.                 elif nextchar in self.commenters:
  91.                     self.instream.readline()
  92.                     self.lineno = self.lineno + 1
  93.                 elif nextchar in self.wordchars or nextchar in self.quotes:
  94.                     self.token = self.token + nextchar
  95.                 else:
  96.                     self.pushback = [nextchar] + self.pushback
  97.                     if self.debug >= 2:
  98.                         print "I see punctuation in word state"
  99.                     self.state = ' '
  100.                     if self.token:
  101.                         break    # emit current token
  102.                     else:
  103.                         continue
  104.                 
  105.         result = self.token
  106.         self.token = ''
  107.         if self.debug >= 1:
  108.             print "Token: " + result
  109.         return result
  110.  
  111. if __name__ == '__main__': 
  112.  
  113.     lexer = shlex()
  114.     while 1:
  115.         tt = lexer.get_token()
  116.         if tt != None:
  117.             print "Token: " + repr(tt)
  118.         else:
  119.             break
  120.  
  121.