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My goal is to have a bash prompt that displays a shortened username, a shortened path in blue, and a counter variable that gets reset every time I mistype a command (which I will check with $?, though this is not strictly the same).

Right now, my ~/.bashrc has:

counter=0
#should increment counter if no errors, else reset counter
PROMPT_COMMAND="if [ $? -eq 0 ]; then ((counter++)); else counter=0; fi"
PS1='(${USER:0:3}@\[\e[0;34m\]$(basename $(dirname $PWD))/$(basename $PWD)\[\e[m\])[$counter]\\$ '

This displays:

(use@//home)[17]$

My main problem is that counter is never reset to zero when I get a nonzero exit status. I can run the command in PROMPT_COMMAND after a failed command such as aasdjfasdf and echo $counter will show a 0 (actually, a 1, since PROMPT_COMMAND increments it immediately).

My other lesser problem is that in the root directory my prompt will display

(use@///)[11]$

which is less than ideal (the 3 /'s). I'm not sure how to fix that either, but at least it's not as big of a deal.

How do I get PROMPT_COMMAND to correctly increment and reset counter?

edit: Here is my PS1 that does everything I want, in case others are curious:

counter=0
PROMPT_COMMAND='if [ $? -eq 0 ]; then ((counter++)); else counter=0; fi;'
PS1='(\[\e[4m\]${USER:0:3}\[\e[0m\]@\[\e[34m\]${PWD:${#PWD}<15?0:(-15)}\[\e[m\])[$counter]\\$ '
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  • @Sinjai, you are wrong. Have you tried this? May 11, 2022 at 19:16
  • I am wrong – I tested it, but poorly. Classic single vs double quotes issue. If you define PS1 properly as you've shown above, $counter will remain in the string verbatim and be re-expanded each time $PS1 is used by the shell, as intended. I'm going to delete my comment to avoid wasting future visitors' time (and out of shame).
    – Sinjai
    May 11, 2022 at 22:37

1 Answer 1

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Change PROMPT_COMMAND to be:

PROMPT_COMMAND='if [ $? -eq 0 ]; then counter=$((counter+1)); else counter=0; fi'

Use single-quotes to prevent premature expansion of $?, and use direct assignment for the incremented value of counter.

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  • 1
    This would increment the counter even if you just press Enter.
    – Kusalananda
    Mar 30, 2018 at 8:57

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