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pathfix.py
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#! /usr/bin/python3.9 # Change the #! line (shebang) 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. # Sometimes you may find shebangs with flags such as `#! /usr/bin/env python -si`. # Normally, pathfix overwrites the entire line, including the flags. # To change interpreter and keep flags from the original shebang line, use -k. # If you want to keep flags and add to them one single literal flag, use option -a. # 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 keep_flags = False add_flags = b'' def main(): global new_interpreter global preserve_timestamps global create_backup global keep_flags global add_flags usage = ('usage: %s -i /interpreter -p -n -k -a file-or-directory ...\n' % sys.argv[0]) try: opts, args = getopt.getopt(sys.argv[1:], 'i:a:kpn') 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 o == '-k': keep_flags = True if o == '-a': add_flags = a.encode() if b' ' in add_flags: err("-a option doesn't support whitespaces") sys.exit(2) 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 with f: line = f.readline() fixed = fixline(line) if line == fixed: rep(filename+': no change\n') return head, tail = os.path.split(filename) tempname = os.path.join(head, '@' + tail) try: g = open(tempname, 'wb') except IOError as msg: err('%s: cannot create: %r\n' % (tempname, msg)) return 1 with g: rep(filename + ': updating\n') g.write(fixed) BUFSIZE = 8*1024 while 1: buf = f.read(BUFSIZE) if not buf: break g.write(buf) # 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 parse_shebang(shebangline): shebangline = shebangline.rstrip(b'\n') start = shebangline.find(b' -') if start == -1: return b'' return shebangline[start:] def populate_flags(shebangline): old_flags = b'' if keep_flags: old_flags = parse_shebang(shebangline) if old_flags: old_flags = old_flags[2:] if not (old_flags or add_flags): return b'' # On Linux, the entire string following the interpreter name # is passed as a single argument to the interpreter. # e.g. "#! /usr/bin/python3 -W Error -s" runs "/usr/bin/python3 "-W Error -s" # so shebang should have single '-' where flags are given and # flag might need argument for that reasons adding new flags is # between '-' and original flags # e.g. #! /usr/bin/python3 -sW Error return b' -' + add_flags + old_flags def fixline(line): if not line.startswith(b'#!'): return line if b"python" not in line: return line flags = populate_flags(line) return b'#! ' + new_interpreter + flags + b'\n' if __name__ == '__main__': main()