Eric Raymond:
Added and documented the capability for shlex to handle lexical-level inclusion and a stack of input sources. Also, the input stream member is now documented, and the constructor takes an optional source-filename. The class provides facilities to generate error messages that track file and line number. [GvR: I changed the __main__ code so that it actually stops at EOF, as Eric surely intended -- however it returned '' instead of the None he was testing for.]
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Guido van Rossum
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Lib/shlex.py
81
Lib/shlex.py
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@ -1,16 +1,19 @@
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"""A lexical analyzer class for simple shell-like syntaxes."""
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# Module and documentation by Eric S. Raymond, 21 Dec 1998
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# Input stacking and error message cleanup added by ESR, March 2000
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import sys
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class shlex:
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"A lexical analyzer class for simple shell-like syntaxes."
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def __init__(self, instream=None):
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def __init__(self, instream=None, infile=None):
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if instream:
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self.instream = instream
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self.infile = infile
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else:
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self.instream = sys.stdin
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self.infile = None
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self.commenters = '#'
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self.wordchars = 'abcdfeghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
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self.whitespace = ' \t\r\n'
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@ -20,37 +23,76 @@ class shlex:
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self.lineno = 1
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self.debug = 0
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self.token = ''
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self.filestack = []
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self.source = None
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if self.debug:
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print 'shlex: reading from %s, line %d' % (self.instream,self.lineno)
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def push_token(self, tok):
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"Push a token onto the stack popped by the get_token method"
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if (self.debug >= 1):
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print "Pushing " + tok
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if self.debug >= 1:
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print "shlex: pushing token " + `tok`
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self.pushback = [tok] + self.pushback;
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def get_token(self):
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"Get a token from the input stream (or from stack if it's monempty)"
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"Get a token from the input stream (or from stack if it's nonempty)"
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if self.pushback:
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tok = self.pushback[0]
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self.pushback = self.pushback[1:]
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if (self.debug >= 1):
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print "Popping " + tok
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if self.debug >= 1:
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print "shlex: popping token " + `tok`
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return tok
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# No pushback. Get a token.
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raw = self.read_token()
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# Handle inclusions
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while raw == self.source:
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(newfile, newstream) = self.sourcehook(self.read_token())
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self.filestack = [(self.infile,self.instream,self.lineno)] + self.filestack
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self.infile = newfile
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self.instream = newstream
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self.lineno = 1
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if self.debug:
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print 'shlex: pushing to file %s' % (self.infile,)
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raw = self.get_token()
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# Maybe we got EOF instead?
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while raw == "":
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if len(self.filestack) == 0:
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return ""
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else:
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self.instream.close()
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(self.infile, self.instream, self.lineno) = self.filestack[0]
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self.filestack = self.filestack[1:]
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if self.debug:
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print 'shlex: popping to %s, line %d' % (self.instream, self.lineno)
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self.state = ' '
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raw = self.get_token()
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# Neither inclusion nor EOF
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if self.debug >= 1:
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if raw:
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print "shlex: token=" + `raw`
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else:
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print "shlex: token=EOF"
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return raw
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def read_token(self):
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"Read a token from the input stream (no pushback or inclusions)"
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tok = ''
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while 1:
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nextchar = self.instream.read(1);
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if nextchar == '\n':
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self.lineno = self.lineno + 1
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if self.debug >= 3:
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print "In state " + repr(self.state) + " I see character: " + repr(nextchar)
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print "shlex: in state " + repr(self.state) + " I see character: " + repr(nextchar)
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if self.state == None:
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return ''
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self.token = ''; # past end of file
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break
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elif self.state == ' ':
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if not nextchar:
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self.state = None; # end of file
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break
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elif nextchar in self.whitespace:
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if self.debug >= 2:
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print "I see whitespace in whitespace state"
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print "shlex: I see whitespace in whitespace state"
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if self.token:
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break # emit current token
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else:
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@ -81,7 +123,7 @@ class shlex:
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break
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elif nextchar in self.whitespace:
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if self.debug >= 2:
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print "I see whitespace in word state"
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print "shlex: I see whitespace in word state"
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self.state = ' '
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if self.token:
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break # emit current token
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@ -95,26 +137,33 @@ class shlex:
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else:
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self.pushback = [nextchar] + self.pushback
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if self.debug >= 2:
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print "I see punctuation in word state"
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print "shlex: I see punctuation in word state"
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self.state = ' '
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if self.token:
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break # emit current token
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else:
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continue
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result = self.token
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self.token = ''
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if self.debug >= 1:
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print "Token: " + result
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if self.debug > 1:
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if result:
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print "shlex: raw token=" + `result`
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else:
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print "shlex: raw token=EOF"
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return result
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def sourcehook(self, newfile):
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"Hook called on a filename to be sourced."
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if newfile[0] == '"':
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newfile = newfile[1:-1]
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return (newfile, open(newfile, "r"))
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if __name__ == '__main__':
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lexer = shlex()
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while 1:
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tt = lexer.get_token()
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if tt != None:
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print "Token: " + repr(tt)
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else:
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if not tt:
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break
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