clone of moreutils errno(1)

errno.py

import errno
import os
import sys

def main():
    exitcode = 0
    errorcode_inverse = {v: k for k, v in errno.errorcode.items()}

    for arg in sys.argv[1:]:
        try:
            num = int(arg)
        except ValueError:
            code = arg
            num = errorcode_inverse.get(code)
            if num is None:
                print("ERROR: Not understood:", arg)
                exitcode = 1
                continue
        else:
            code = errno.errorcode.get(num)
            if code is None:
                exitcode = 1
                continue

        try:
            message = os.strerror(num)
        except ValueError:
            exitcode = 1
            continue

        print(code, num, message)

    exit(exitcode)

if __name__ == "__main__":
    main()