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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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# push_source() and pop_source() made explicit by ESR, January 2001.
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import os.path
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import sys
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__all__ = ["shlex"]
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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, 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 = ('abcdfeghijklmnopqrstuvwxyz'
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'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_')
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self.whitespace = ' \t\r\n'
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self.quotes = '\'"'
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self.state = ' '
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self.pushback = []
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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' \
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% (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 "shlex: pushing token " + `tok`
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self.pushback = [tok] + self.pushback
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def push_source(self, newstream, newfile=None):
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"Push an input source onto the lexer's input source stack."
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self.filestack.insert(0, (self.infile, self.instream, self.lineno))
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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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if newfile:
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print 'shlex: pushing to file %s' % (self.infile,)
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else:
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print 'shlex: pushing to stream %s' % (self.instream,)
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def pop_source(self):
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"Pop the input source stack."
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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' \
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% (self.instream, self.lineno)
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self.state = ' '
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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 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 "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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spec = self.sourcehook(self.read_token())
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if spec:
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(newfile, newstream) = spec
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self.push_source(newstream, newfile)
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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.pop_source()
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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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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 "shlex: in state", repr(self.state), \
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"I see character:", repr(nextchar)
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if self.state is None:
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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 "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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continue
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elif nextchar in self.commenters:
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self.instream.readline()
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self.lineno = self.lineno + 1
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elif nextchar in self.wordchars:
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self.token = nextchar
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self.state = 'a'
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elif nextchar in self.quotes:
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self.token = nextchar
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self.state = nextchar
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else:
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self.token = nextchar
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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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elif self.state in self.quotes:
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self.token = self.token + nextchar
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if nextchar == self.state:
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self.state = ' '
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break
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elif not nextchar: # end of file
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if self.debug >= 2:
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print "shlex: I see EOF in quotes state"
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# XXX what error should be raised here?
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raise ValueError, "No closing quotation"
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elif self.state == 'a':
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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 "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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else:
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continue
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elif nextchar in self.commenters:
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self.instream.readline()
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self.lineno = self.lineno + 1
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elif nextchar in self.wordchars or nextchar in self.quotes:
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self.token = self.token + nextchar
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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 "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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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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# This implements cpp-like semantics for relative-path inclusion.
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if type(self.infile) == type("") and not os.path.isabs(newfile):
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newfile = os.path.join(os.path.dirname(self.infile), newfile)
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return (newfile, open(newfile, "r"))
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def error_leader(self, infile=None, lineno=None):
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"Emit a C-compiler-like, Emacs-friendly error-message leader."
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if not infile:
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infile = self.infile
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if not lineno:
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lineno = self.lineno
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return "\"%s\", line %d: " % (infile, lineno)
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if __name__ == '__main__':
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if len(sys.argv) == 1:
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lexer = shlex()
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else:
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file = sys.argv[1]
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lexer = shlex(open(file), file)
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while 1:
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tt = lexer.get_token()
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if tt:
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print "Token: " + repr(tt)
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else:
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break
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