Bash prompt PS1 newline must be conditional

Question

How do we have PS1 newline \n being conditional on whether previous Bash variable's one, as this cannot succeed:

foo=

 NEWLINE=
 #...
 ((foo)) && {
  THELINE=foobar
  NEWLINE='\n'
 }

PS1='$(echo $THELINE)$NEWLINE\w-$ '

if foo not 0 then THELINE is "foobar" with a newline, otherwise whatever THELINE is it musn't be given \n

sincere useful help valuable

`$.............``

Please read [correct-bash-and-shell-script-variable-capitalization](https://stackoverflow.com/questions/673055/correct-bash-and-shell-script-variable-capitalization) and then fix your variable names. — Ed Morton, May 14 '23 at 15:32
Do you want `foo` to be tested once where `PS1` is declared or every time the value of `PS1` is printed? — Ed Morton, May 14 '23 at 15:58

score 4 · Answer 1 · answered May 14 '23 at 05:01

You can use PROMPT_COMMAND to make bash call a function before every prompt.

Unfortunately, I do not understand what you are trying to do so I can't show you exactly how to do what you want. This should get you started though:

prompt_cmd() {
    if [[ condition ]]; then
        PS1="true_prompt$ "
    else
        PS1="false_prompt$ "
    fi
}
export PROMPT_COMMAND=prompt_cmd

score 0 · Accepted Answer · answered May 14 '23 at 07:03

0

You can put the logic directly in PS1 as :

PS1='$(((foo)) && echo $"foobar\n\r" || echo "no") \$ '

example:

$ PS1='$(((foo)) && echo $"foobar\n\r" || echo "no") \$ '
no $ foo=1
foobar
 $

answered May 14 '23 at 07:03

Philippe

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Bash prompt PS1 newline must be conditional

2 Answers2