9

How can I create a bash and a zsh prompt that shows only the current directory and its parent directory?

For example, if I'm at the dir ~/pictures/photos/2021, it should show:

[photos/2021]$ echo hi

That's all. Would like it for bash and for zsh.

Improve this question
1

2 Answers 2

Reset to default
13

In zsh:

PS1='[%2d] $ '

See info zsh 'prompt expansion' for details.

In bash (or zsh -o promptsubst, though you wouldn't want to do that there as if $PWD contains % characters, that would cause further prompt expansions):

PS1='[${PWD#"${PWD%/*/*}/"}] $ '
Improve this answer
10
  • how PWD expand within single quotes? or maybe it does differently for the PS1 or prompts? really I cannot understand how it is expanded!
    – αғsнιη
    May 24, 2021 at 13:30
  • @αғsнιη, it's not expanded at the time of assignment, but it's expanded each time the prompt is expanded as part of the prompt expansion.
    – Stéphane Chazelas
    May 24, 2021 at 13:36
  • seems it removes outer quotes then perform variable expansions, etc, is it safe? looks for me it's unsafe if one don't know what they do with it. I didn't know this until today! like for a directory named ; reboot;
    – αғsнιη
    May 24, 2021 at 13:37
  • 3
    @αғsнιη, it's as safe as your $PS1 is. If you set PS1='$(reboot)', then it will reboot of course. That's why you don't want to set $PS1 to arbitrary values without sanitizing them as part of your PROMPT_COMMAND in bash. In zsh, if you enable the promptsubst option, it's a bit worse in that %x expansions are done after those expansions. It's safer to use the $psvar array and precmd() there than enabling prompsubst.
    – Stéphane Chazelas
    May 24, 2021 at 13:43
  • 2
    @αғsнιη, PS1='$PWD' is safe in that case in that expansion is not going to be done recursively. $PWD will be expanded to its value, but if that value has some $s or backticks, that will not be further expanded. The prompt would be if you your $PROMPT_COMMAND does something like PS1="$PWD ... " (note the double quotes)
    – Stéphane Chazelas
    May 24, 2021 at 13:52
2

Another option that may be more readable:

PS1='[$(basename $(dirname "$PWD"))/$(basename "$PWD")]'

This also shows how you do similar directory operations more generally.

Improve this answer
1
  • 3
    Note that that solution is for bash or other shells that perform other expansions upon prompt expansions. There's a minor glitch in that it gives /// when you're in / or //etc when in /etc for instance. It does strip trailing newline characters in those path components. It means starting at least 3 processes and executing three external processes in them at each prompt. So in the end, I wouldn't go for that approach.
    – Stéphane Chazelas
    May 25, 2021 at 5:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.