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
22import sys
23import re
24import os
25from stat import *
26import getopt
27
28err = sys.stderr.write
29dbg = err
30rep = sys.stdout.write
31
32new_interpreter = None
33
34def 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
62ispythonprog = re.compile('^[a-zA-Z0-9_]+\.py$')
63def ispython(name):
64    return ispythonprog.match(name) >= 0
65
66def 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
88def 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
141def 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
148if __name__ == '__main__':
149    main()
150