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      1 #! /usr/bin/env python
      2 
      3 # Change the #! line occurring in Python scripts.  The new interpreter
      4 # pathname must be given with a -i option.
      5 #
      6 # Command line arguments are files or directories to be processed.
      7 # Directories are searched recursively for files whose name looks
      8 # like a python module.
      9 # Symbolic links are always ignored (except as explicit directory
     10 # arguments).  Of course, the original file is kept as a back-up
     11 # (with a "~" attached to its name).
     12 #
     13 # Undoubtedly you can do this using find and sed or perl, but this is
     14 # a nice example of Python code that recurses down a directory tree
     15 # and uses regular expressions.  Also note several subtleties like
     16 # preserving the file's mode and avoiding to even write a temp file
     17 # when no changes are needed for a file.
     18 #
     19 # NB: by changing only the function fixfile() you can turn this
     20 # into a program for a different change to Python programs...
     21 
     22 import sys
     23 import re
     24 import os
     25 from stat import *
     26 import getopt
     27 
     28 err = sys.stderr.write
     29 dbg = err
     30 rep = sys.stdout.write
     31 
     32 new_interpreter = None
     33 
     34 def main():
     35     global new_interpreter
     36     usage = ('usage: %s -i /interpreter file-or-directory ...\n' %
     37              sys.argv[0])
     38     try:
     39         opts, args = getopt.getopt(sys.argv[1:], 'i:')
     40     except getopt.error, msg:
     41         err(msg + '\n')
     42         err(usage)
     43         sys.exit(2)
     44     for o, a in opts:
     45         if o == '-i':
     46             new_interpreter = a
     47     if not new_interpreter or new_interpreter[0] != '/' or not args:
     48         err('-i option or file-or-directory missing\n')
     49         err(usage)
     50         sys.exit(2)
     51     bad = 0
     52     for arg in args:
     53         if os.path.isdir(arg):
     54             if recursedown(arg): bad = 1
     55         elif os.path.islink(arg):
     56             err(arg + ': will not process symbolic links\n')
     57             bad = 1
     58         else:
     59             if fix(arg): bad = 1
     60     sys.exit(bad)
     61 
     62 ispythonprog = re.compile('^[a-zA-Z0-9_]+\.py$')
     63 def ispython(name):
     64     return ispythonprog.match(name) >= 0
     65 
     66 def recursedown(dirname):
     67     dbg('recursedown(%r)\n' % (dirname,))
     68     bad = 0
     69     try:
     70         names = os.listdir(dirname)
     71     except os.error, msg:
     72         err('%s: cannot list directory: %r\n' % (dirname, msg))
     73         return 1
     74     names.sort()
     75     subdirs = []
     76     for name in names:
     77         if name in (os.curdir, os.pardir): continue
     78         fullname = os.path.join(dirname, name)
     79         if os.path.islink(fullname): pass
     80         elif os.path.isdir(fullname):
     81             subdirs.append(fullname)
     82         elif ispython(name):
     83             if fix(fullname): bad = 1
     84     for fullname in subdirs:
     85         if recursedown(fullname): bad = 1
     86     return bad
     87 
     88 def fix(filename):
     89 ##  dbg('fix(%r)\n' % (filename,))
     90     try:
     91         f = open(filename, 'r')
     92     except IOError, msg:
     93         err('%s: cannot open: %r\n' % (filename, msg))
     94         return 1
     95     line = f.readline()
     96     fixed = fixline(line)
     97     if line == fixed:
     98         rep(filename+': no change\n')
     99         f.close()
    100         return
    101     head, tail = os.path.split(filename)
    102     tempname = os.path.join(head, '@' + tail)
    103     try:
    104         g = open(tempname, 'w')
    105     except IOError, msg:
    106         f.close()
    107         err('%s: cannot create: %r\n' % (tempname, msg))
    108         return 1
    109     rep(filename + ': updating\n')
    110     g.write(fixed)
    111     BUFSIZE = 8*1024
    112     while 1:
    113         buf = f.read(BUFSIZE)
    114         if not buf: break
    115         g.write(buf)
    116     g.close()
    117     f.close()
    118 
    119     # Finishing touch -- move files
    120 
    121     # First copy the file's mode to the temp file
    122     try:
    123         statbuf = os.stat(filename)
    124         os.chmod(tempname, statbuf[ST_MODE] & 07777)
    125     except os.error, msg:
    126         err('%s: warning: chmod failed (%r)\n' % (tempname, msg))
    127     # Then make a backup of the original file as filename~
    128     try:
    129         os.rename(filename, filename + '~')
    130     except os.error, msg:
    131         err('%s: warning: backup failed (%r)\n' % (filename, msg))
    132     # Now move the temp file to the original file
    133     try:
    134         os.rename(tempname, filename)
    135     except os.error, msg:
    136         err('%s: rename failed (%r)\n' % (filename, msg))
    137         return 1
    138     # Return success
    139     return 0
    140 
    141 def fixline(line):
    142     if not line.startswith('#!'):
    143         return line
    144     if "python" not in line:
    145         return line
    146     return '#! %s\n' % new_interpreter
    147 
    148 if __name__ == '__main__':
    149     main()
    150