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- #!/usr/bin/env python3
- # Change the #! line occurring in Python scripts. The new interpreter
- # pathname must be given with a -i option.
- #
- # Command line arguments are files or directories to be processed.
- # Directories are searched recursively for files whose name looks
- # like a python module.
- # Symbolic links are always ignored (except as explicit directory
- # arguments).
- # The original file is kept as a back-up (with a "~" attached to its name),
- # -n flag can be used to disable this.
- #
- # Undoubtedly you can do this using find and sed or perl, but this is
- # a nice example of Python code that recurses down a directory tree
- # and uses regular expressions. Also note several subtleties like
- # preserving the file's mode and avoiding to even write a temp file
- # when no changes are needed for a file.
- #
- # NB: by changing only the function fixfile() you can turn this
- # into a program for a different change to Python programs...
- import sys
- import re
- import os
- from stat import *
- import getopt
- err = sys.stderr.write
- dbg = err
- rep = sys.stdout.write
- new_interpreter = None
- preserve_timestamps = False
- create_backup = True
- def main():
- global new_interpreter
- global preserve_timestamps
- global create_backup
- usage = ('usage: %s -i /interpreter -p -n file-or-directory ...\n' %
- sys.argv[0])
- try:
- opts, args = getopt.getopt(sys.argv[1:], 'i:pn')
- except getopt.error as msg:
- err(str(msg) + '\n')
- err(usage)
- sys.exit(2)
- for o, a in opts:
- if o == '-i':
- new_interpreter = a.encode()
- if o == '-p':
- preserve_timestamps = True
- if o == '-n':
- create_backup = False
- if not new_interpreter or not new_interpreter.startswith(b'/') or \
- not args:
- err('-i option or file-or-directory missing\n')
- err(usage)
- sys.exit(2)
- bad = 0
- for arg in args:
- if os.path.isdir(arg):
- if recursedown(arg): bad = 1
- elif os.path.islink(arg):
- err(arg + ': will not process symbolic links\n')
- bad = 1
- else:
- if fix(arg): bad = 1
- sys.exit(bad)
- def ispython(name):
- return name.endswith('.py')
- def recursedown(dirname):
- dbg('recursedown(%r)\n' % (dirname,))
- bad = 0
- try:
- names = os.listdir(dirname)
- except OSError as msg:
- err('%s: cannot list directory: %r\n' % (dirname, msg))
- return 1
- names.sort()
- subdirs = []
- for name in names:
- if name in (os.curdir, os.pardir): continue
- fullname = os.path.join(dirname, name)
- if os.path.islink(fullname): pass
- elif os.path.isdir(fullname):
- subdirs.append(fullname)
- elif ispython(name):
- if fix(fullname): bad = 1
- for fullname in subdirs:
- if recursedown(fullname): bad = 1
- return bad
- def fix(filename):
- ## dbg('fix(%r)\n' % (filename,))
- try:
- f = open(filename, 'rb')
- except IOError as msg:
- err('%s: cannot open: %r\n' % (filename, msg))
- return 1
- line = f.readline()
- fixed = fixline(line)
- if line == fixed:
- rep(filename+': no change\n')
- f.close()
- return
- head, tail = os.path.split(filename)
- tempname = os.path.join(head, '@' + tail)
- try:
- g = open(tempname, 'wb')
- except IOError as msg:
- f.close()
- err('%s: cannot create: %r\n' % (tempname, msg))
- return 1
- rep(filename + ': updating\n')
- g.write(fixed)
- BUFSIZE = 8*1024
- while 1:
- buf = f.read(BUFSIZE)
- if not buf: break
- g.write(buf)
- g.close()
- f.close()
- # Finishing touch -- move files
- mtime = None
- atime = None
- # First copy the file's mode to the temp file
- try:
- statbuf = os.stat(filename)
- mtime = statbuf.st_mtime
- atime = statbuf.st_atime
- os.chmod(tempname, statbuf[ST_MODE] & 0o7777)
- except OSError as msg:
- err('%s: warning: chmod failed (%r)\n' % (tempname, msg))
- # Then make a backup of the original file as filename~
- if create_backup:
- try:
- os.rename(filename, filename + '~')
- except OSError as msg:
- err('%s: warning: backup failed (%r)\n' % (filename, msg))
- else:
- try:
- os.remove(filename)
- except OSError as msg:
- err('%s: warning: removing failed (%r)\n' % (filename, msg))
- # Now move the temp file to the original file
- try:
- os.rename(tempname, filename)
- except OSError as msg:
- err('%s: rename failed (%r)\n' % (filename, msg))
- return 1
- if preserve_timestamps:
- if atime and mtime:
- try:
- os.utime(filename, (atime, mtime))
- except OSError as msg:
- err('%s: reset of timestamp failed (%r)\n' % (filename, msg))
- return 1
- # Return success
- return 0
- def fixline(line):
- if not line.startswith(b'#!'):
- return line
- if b"python" not in line:
- return line
- return b'#! ' + new_interpreter + b'\n'
- if __name__ == '__main__':
- main()
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