Change working directory in shell with a python script

Question

I want to implement a userland command that will take one of its arguments (path) and change the directory to that dir. After the program completion I would like the shell to be in that directory. So I want to implement cd command, but with external program.

Can it be done in a python script or I have to write bash wrapper?

Example:

tdi@bayes:/home/$>python cd.py tdi
tdi@bayes:/home/tdi$>

Answer 1

Others have pointed out that you can't change the working directory of a parent from a child.

But there is a way you can achieve your goal -- if you cd from a shell function, it can change the working dir. Add this to your ~/.bashrc:

go() {
    cd "$(python /path/to/cd.py "$1")"
}

Your script should print the path to the directory that you want to change to. For example, this could be your cd.py:

#!/usr/bin/python
import sys, os.path
if sys.argv[1] == 'tdi': print(os.path.expanduser('~/long/tedious/path/to/tdi'))
elif sys.argv[1] == 'xyz':  print(os.path.expanduser('~/long/tedious/path/to/xyz'))

Then you can do:

tdi@bayes:/home/$> go tdi
tdi@bayes:/home/tdi$> go tdi

Answer 2

That is not going to be possible.

Your script runs in a sub-shell spawned by the parent shell where the command was issued.

Any cd ing done in the sub-shell does not affect the parent shell.

Answer 3

As codaddict writes, what happens in your sub-shell does not affect the parent shell. However, if your goal is present the user with a shell in a different directory, you could always have Python use os.chdir to change the sub-shell's working directory and then launch a new shell from Python. This will not change the working directory of the original shell, but will leave the user with one in a different directory.

Answer 4

cd专门（？）实现为 shell 内部命令，因为任何外部程序都不能更改父 shell 的 CWD。

Answer 5

I shall try to show how to set a Bash terminal's working directory to whatever path a Python program wants in a fairly easy way.

Only Bash can set its working directory, so routines are needed for Python and Bash. The Python program has a routine defined as:

fob=open(somefile,"w")
fob.write(dd)
fob.close()

"Somefile" could for convenience be a RAM disk file. Bash "mount" would show tmpfs mounted somewhere like "/run/user/1000", so somefile might be "/run/user/1000/pythonwkdir". "dd" is the full directory path name desired.

The Bash file would look like:

#!/bin/bash
#pysync ---Command ". pysync" will set bash dir to what Python recorded
cd `cat /run/user/1000/pythonwkdr`