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"""A lexical analyzer class for simple shell-like syntaxes."""
# Module and documentation by Eric S. Raymond, 21 Dec 1998
# Input stacking and error message cleanup added by ESR, March 2000
import os.path
import sys
class shlex:
"A lexical analyzer class for simple shell-like syntaxes."
def __init__(self, instream=None, infile=None):
if instream:
self.instream = instream
self.infile = infile
else:
self.instream = sys.stdin
self.infile = None
self.commenters = '#'
self.wordchars = 'abcdfeghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
self.whitespace = ' \t\r\n'
self.quotes = '\'"'
self.state = ' '
self.pushback = [];
self.lineno = 1
self.debug = 0
self.token = ''
self.filestack = []
self.source = None
if self.debug:
print 'shlex: reading from %s, line %d' \
% (self.instream, self.lineno)
def push_token(self, tok):
"Push a token onto the stack popped by the get_token method"
if self.debug >= 1:
print "shlex: pushing token " + `tok`
self.pushback = [tok] + self.pushback;
def get_token(self):
"Get a token from the input stream (or from stack if it's nonempty)"
if self.pushback:
tok = self.pushback[0]
self.pushback = self.pushback[1:]
if self.debug >= 1:
print "shlex: popping token " + `tok`
return tok
# No pushback. Get a token.
raw = self.read_token()
# Handle inclusions
while raw == self.source:
(newfile, newstream) = self.sourcehook(self.read_token())
self.filestack.insert(0, (self.infile, self.instream, self.lineno))
self.infile = newfile
self.instream = newstream
self.lineno = 1
if self.debug:
print 'shlex: pushing to file %s' % (self.infile,)
raw = self.get_token()
# Maybe we got EOF instead?
while raw == "":
if len(self.filestack) == 0:
return ""
else:
self.instream.close()
(self.infile, self.instream, self.lineno) = self.filestack[0]
self.filestack = self.filestack[1:]
if self.debug:
print 'shlex: popping to %s, line %d' \
% (self.instream, self.lineno)
self.state = ' '
raw = self.get_token()
# Neither inclusion nor EOF
if self.debug >= 1:
if raw:
print "shlex: token=" + `raw`
else:
print "shlex: token=EOF"
return raw
def read_token(self):
"Read a token from the input stream (no pushback or inclusions)"
tok = ''
while 1:
nextchar = self.instream.read(1);
if nextchar == '\n':
self.lineno = self.lineno + 1
if self.debug >= 3:
print "shlex: in state", repr(self.state), \
"I see character:", repr(nextchar)
if self.state == None:
self.token = ''; # past end of file
break
elif self.state == ' ':
if not nextchar:
self.state = None; # end of file
break
elif nextchar in self.whitespace:
if self.debug >= 2:
print "shlex: I see whitespace in whitespace state"
if self.token:
break # emit current token
else:
continue
elif nextchar in self.commenters:
self.instream.readline()
self.lineno = self.lineno + 1
elif nextchar in self.wordchars:
self.token = nextchar
self.state = 'a'
elif nextchar in self.quotes:
self.token = nextchar
self.state = nextchar
else:
self.token = nextchar
if self.token:
break # emit current token
else:
continue
elif self.state in self.quotes:
self.token = self.token + nextchar
if nextchar == self.state:
self.state = ' '
break
elif self.state == 'a':
if not nextchar:
self.state = None; # end of file
break
elif nextchar in self.whitespace:
if self.debug >= 2:
print "shlex: I see whitespace in word state"
self.state = ' '
if self.token:
break # emit current token
else:
continue
elif nextchar in self.commenters:
self.instream.readline()
self.lineno = self.lineno + 1
elif nextchar in self.wordchars or nextchar in self.quotes:
self.token = self.token + nextchar
else:
self.pushback = [nextchar] + self.pushback
if self.debug >= 2:
print "shlex: I see punctuation in word state"
self.state = ' '
if self.token:
break # emit current token
else:
continue
result = self.token
self.token = ''
if self.debug > 1:
if result:
print "shlex: raw token=" + `result`
else:
print "shlex: raw token=EOF"
return result
def sourcehook(self, newfile):
"Hook called on a filename to be sourced."
if newfile[0] == '"':
newfile = newfile[1:-1]
# This implements cpp-like semantics for relative-path inclusion.
if type(self.infile) == type("") and not os.path.isabs(newfile):
newfile = os.path.join(os.path.dirname(self.infile), newfile)
return (newfile, open(newfile, "r"))
def error_leader(self, infile=None, lineno=None):
"Emit a C-compiler-like, Emacs-friendly error-message leader."
if not infile:
infile = self.infile
if not lineno:
lineno = self.lineno
return "\"%s\", line %d: " % (infile, lineno)
if __name__ == '__main__':
if len(sys.argv) == 1:
lexer = shlex()
else:
file = sys.argv[1]
lexer = shlex(open(file), file)
while 1:
tt = lexer.get_token()
if tt:
print "Token: " + repr(tt)
else:
break
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