#! /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 sysimport reimport osfrom stat import *import getopt err = sys.stderr.writedbg = errrep = 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()