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Python Source  |  2000-05-02  |  6.4 KB  |  178 lines
  1. """A lexical analyzer class for simple shell-like syntaxes."""
  2.  
  3. # Module and documentation by Eric S. Raymond, 21 Dec 1998 
  4. # Input stacking and error message cleanup added by ESR, March 2000
  5.  
  6. import sys
  7.  
  8. class shlex:
  9.     "A lexical analyzer class for simple shell-like syntaxes." 
  10.     def __init__(self, instream=None, infile=None):
  11.         if instream:
  12.             self.instream = instream
  13.             self.infile = infile
  14.         else:
  15.             self.instream = sys.stdin
  16.             self.infile = None
  17.         self.commenters = '#'
  18.         self.wordchars = 'abcdfeghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
  19.         self.whitespace = ' \t\r\n'
  20.         self.quotes = '\'"'
  21.         self.state = ' '
  22.         self.pushback = [];
  23.         self.lineno = 1
  24.         self.debug = 0
  25.         self.token = ''
  26.     self.filestack = []
  27.         self.source = None
  28.         if self.debug:
  29.             print 'shlex: reading from %s, line %d' % (self.instream,self.lineno)
  30.  
  31.     def push_token(self, tok):
  32.         "Push a token onto the stack popped by the get_token method"
  33.         if self.debug >= 1:
  34.             print "shlex: pushing token " + `tok`
  35.         self.pushback = [tok] + self.pushback;
  36.  
  37.     def get_token(self):
  38.         "Get a token from the input stream (or from stack if it's nonempty)"
  39.         if self.pushback:
  40.             tok = self.pushback[0]
  41.             self.pushback = self.pushback[1:]
  42.             if self.debug >= 1:
  43.                 print "shlex: popping token " + `tok`
  44.             return tok
  45.     # No pushback.  Get a token.
  46.         raw = self.read_token()
  47.         # Handle inclusions
  48.         while raw == self.source:
  49.             (newfile, newstream) = self.sourcehook(self.read_token())
  50.             self.filestack = [(self.infile,self.instream,self.lineno)] + self.filestack
  51.             self.infile = newfile
  52.             self.instream = newstream
  53.             self.lineno = 1
  54.             if self.debug:
  55.                 print 'shlex: pushing to file %s' % (self.infile,)
  56.             raw = self.get_token()
  57.         # Maybe we got EOF instead?
  58.         while raw == "":
  59.             if len(self.filestack) == 0:
  60.                 return ""
  61.             else:
  62.                 self.instream.close()
  63.                 (self.infile, self.instream, self.lineno) = self.filestack[0]
  64.                 self.filestack = self.filestack[1:]
  65.                 if self.debug:
  66.                     print 'shlex: popping to %s, line %d' % (self.instream, self.lineno)
  67.                 self.state = ' '
  68.                 raw = self.get_token()
  69.          # Neither inclusion nor EOF
  70.         if self.debug >= 1:
  71.             if raw:
  72.                 print "shlex: token=" + `raw`
  73.             else:
  74.                 print "shlex: token=EOF"
  75.         return raw
  76.  
  77.     def read_token(self):
  78.         "Read a token from the input stream (no pushback or inclusions)"
  79.         tok = ''
  80.         while 1:
  81.             nextchar = self.instream.read(1);
  82.             if nextchar == '\n':
  83.                 self.lineno = self.lineno + 1
  84.             if self.debug >= 3:
  85.                 print "shlex: in state " + repr(self.state) + " I see character: " + repr(nextchar) 
  86.             if self.state == None:
  87.                 self.token = '';    # past end of file
  88.                 break
  89.             elif self.state == ' ':
  90.                 if not nextchar:
  91.                     self.state = None;    # end of file
  92.                     break
  93.                 elif nextchar in self.whitespace:
  94.                     if self.debug >= 2:
  95.                         print "shlex: I see whitespace in whitespace state"
  96.                     if self.token:
  97.                         break    # emit current token
  98.                     else:
  99.                         continue
  100.                 elif nextchar in self.commenters:
  101.                     self.instream.readline()
  102.                     self.lineno = self.lineno + 1
  103.                 elif nextchar in self.wordchars:
  104.                     self.token = nextchar
  105.                     self.state = 'a'
  106.                 elif nextchar in self.quotes:
  107.                     self.token = nextchar
  108.                     self.state = nextchar
  109.                 else:
  110.                     self.token = nextchar
  111.                     if self.token:
  112.                         break    # emit current token
  113.                     else:
  114.                         continue
  115.             elif self.state in self.quotes:
  116.                 self.token = self.token + nextchar
  117.                 if nextchar == self.state:
  118.                     self.state = ' '
  119.                     break
  120.             elif self.state == 'a':
  121.                 if not nextchar:
  122.                     self.state = None;    # end of file
  123.                     break
  124.                 elif nextchar in self.whitespace:
  125.                     if self.debug >= 2:
  126.                         print "shlex: I see whitespace in word state"
  127.                     self.state = ' '
  128.                     if self.token:
  129.                         break    # emit current token
  130.                     else:
  131.                         continue
  132.                 elif nextchar in self.commenters:
  133.                     self.instream.readline()
  134.                     self.lineno = self.lineno + 1
  135.                 elif nextchar in self.wordchars or nextchar in self.quotes:
  136.                     self.token = self.token + nextchar
  137.                 else:
  138.                     self.pushback = [nextchar] + self.pushback
  139.                     if self.debug >= 2:
  140.                         print "shlex: I see punctuation in word state"
  141.                     self.state = ' '
  142.                     if self.token:
  143.                         break    # emit current token
  144.                     else:
  145.                         continue
  146.         result = self.token
  147.         self.token = ''
  148.         if self.debug > 1:
  149.             if result:
  150.                 print "shlex: raw token=" + `result`
  151.             else:
  152.                 print "shlex: raw token=EOF"
  153.         return result
  154.  
  155.     def sourcehook(self, newfile):
  156.         "Hook called on a filename to be sourced."
  157.         if newfile[0] == '"':
  158.             newfile = newfile[1:-1]
  159.         return (newfile, open(newfile, "r"))
  160.  
  161.     def error_leader(self, infile=None, lineno=None):
  162.         "Emit a C-compiler-like, Emacs-friendly error-message leader."
  163.         if not infile:
  164.             infile = self.infile
  165.         if not lineno:
  166.             lineno = self.lineno
  167.         return "\"%s\", line %d: " % (infile, lineno)
  168.  
  169. if __name__ == '__main__': 
  170.  
  171.     lexer = shlex()
  172.     while 1:
  173.         tt = lexer.get_token()
  174.         print "Token: " + repr(tt)
  175.         if not tt:
  176.             break
  177.  
  178.