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#! /usr/bin/env python

# 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). Of course, the original file is kept as a back-up

# (with a "~" attached to its name).

#

# 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

def main():

global new_interpreter

usage = ('usage: %s -i /interpreter file-or-directory ...\n' %

sys.argv[0])

try:

opts, args = getopt.getopt(sys.argv[1:], 'i:')

except getopt.error, msg:

err(msg + '\n')

err(usage)

sys.exit(2)

for o, a in opts:

if o == '-i':

new_interpreter = a

if not new_interpreter or new_interpreter[0] != '/' 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)

ispythonprog = re.compile('^[a-zA-Z0-9_]+\.py$')

def ispython(name):

return ispythonprog.match(name) >= 0

def recursedown(dirname):

dbg('recursedown(%r)\n' % (dirname,))

bad = 0

try:

names = os.listdir(dirname)

except os.error, 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, 'r')

except IOError, 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, 'w')

except IOError, 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

# First copy the file's mode to the temp file

try:

statbuf = os.stat(filename)

os.chmod(tempname, statbuf[ST_MODE] & 07777)

except os.error, msg:

err('%s: warning: chmod failed (%r)\n' % (tempname, msg))

# Then make a backup of the original file as filename~

try:

os.rename(filename, filename + '~')

except os.error, msg:

err('%s: warning: backup failed (%r)\n' % (filename, msg))

# Now move the temp file to the original file

try:

os.rename(tempname, filename)

except os.error, msg:

err('%s: rename failed (%r)\n' % (filename, msg))

return 1

# Return succes

return 0

def fixline(line):

if not line.startswith('#!'):

return line

if "python" not in line:

return line

return '#! %s\n' % new_interpreter

if __name__ == '__main__':

main()