ren

#!/usr/bin/python3

import os
import readline
import sys

def input_with_prefill(prompt, text):
        def hook():
            readline.insert_text(text)
            readline.redisplay()
        readline.set_pre_input_hook(hook)

        if sys.version_info >= (3,):
            result = input(prompt)
        else:
            result = raw_input(prompt)

        readline.set_pre_input_hook()
        return result

if len(sys.argv) == 1:
    raise ValueError("usage ren <FILENAME>")

source = sys.argv[1]
if source == "":
    raise ValueError("empty filename")
if not os.path.exists(source):
    raise ValueError(source, " file does not exists")

out = input_with_prefill('new name: ', source)

if out == source:
    print("same name, do mothing.")
    sys.exit(0)

if out == "":
    raise ValueError("out filename cannot be empty")

print(f"rename from:[{source}]")
print(f"rename to:[{out}]")
ok = input("rename ? y/n[Y]: ") or "Y"

if ok == "Y":
    os.rename(source, out)
else:
    print("canceled")