Include non-0 exit codes in the subsequent bash prompt

Question

Occasionally, I will run a command that has a lot of output. Occasionally, the last 30-40 lines of that output (a.k.a. the only part of the output I ever really see) is fine, but much further up, there was an error. I'd like to make it easier to notice that the command failed. To do so, I want the return code to be part of my prompt. So I took my $PS1:

[\D{%Y-%m-%d} \t] \[\e]0;\u@\h: \w\a\]\$

...and extended it to this:

[\D{%Y-%m-%d} \t] ${?/^0$/} \[\e]0;\u@\h: \w\a\]\$

This results in a prompt like this:

[2011-05-10 09:38:07] 0 soren@lenny:~$

However, I'd like to find a way to have it only include the exit code if it was non-0. How can I do that? Sure, I could use

$(echo \$? | sed -e blah)

but as lightweight as sed is, it's still quite a bit more heavy weight than bash's builtin stuff.

Cross-side dupe: http://unix.stackexchange.com/q/23515/154731 — GingerPlusPlus, Mar 21 '16 at 18:16

score 12 · Accepted Answer · answered May 10 '11 at 07:55

12

A little bit of printf abuse:

printf '%.*s' $? $?

answered May 10 '11 at 07:55

Ignacio Vazquez-Abrams

776,304
153
1,341
1,358

2

This both works and made me chuckle. I like it. I extended it slightly to this: `printf '%.*s%.*s' $? $? $? ' '` This make it add a space only if it's non-zero. – Soren May 10 '11 at 09:26
For the sake of copmleteness: using $(foo) in the primpt only evaluates foo once (not at each command). See http://stackoverflow.com/questions/16715103/bash-prompt-with-last-exit-code to see how to work around that. – sitaktif Sep 24 '13 at 06:28
1

Explanation: [What does “%.*s” mean in printf?](http://stackoverflow.com/q/7899119) – GingerPlusPlus Mar 07 '16 at 17:33

score 8 · Answer 2 · edited Jun 20 '20 at 09:12

8

The following works for me:

PS1="[\D{%Y-%m-%d} \t] \u@\h:\w\a \${?##0} \$ "

example when $? is 0:

[2011-07-25 11:56:57] plars@plars-t500:~  $<br>
there is an extra space there ---------^^ not sure if that's a problem for you

example when $? is 130:

[2011-07-25 11:57:39] plars@plars-t500:~ 130 $

edited Jun 20 '20 at 09:12

Community

1
1

answered Jul 25 '11 at 17:00

pwlars

516
5
4

score 6 · Answer 3 · answered May 10 '11 at 08:01

6

You could use bash's built in pattern matching:

$ rc=0
$ echo ${rc##0}

$ rc=123
$ echo ${rc##0}
123

answered May 10 '11 at 08:01

überjesus

824
7
9

This was my first thought as well, but I rejected it thinking it would just strip off any 0's, but of course that's not the case. This seems to do the trick. The only downside is the superfluous space in case of a 0 exit code. – Soren May 10 '11 at 09:23
If you want to learn more about this, look under the Substring Removal section at http://www.tldp.org/LDP/abs/html/string-manipulation.html – wisbucky Mar 09 '17 at 19:07

score 4 · Answer 4 · answered May 10 '11 at 08:00

Here's what I use in my .bashrc to get a red number with the exit code. Verbose, but it gets the job done and should be portable.

highlight()
{
    if [ -x /usr/bin/tput ]
    then
        tput bold
        tput setaf $1
    fi
    shift
    printf -- "$@"
    if [ -x /usr/bin/tput ]
    then
        tput sgr0
    fi
}

highlight_error()
{
    highlight 1 "$@"
}

highlight_exit_code()
{
    exit_code=$?
    if [ $exit_code -ne 0 ]
    then
        highlight_error "$exit_code "
    fi
}

PS1='$(highlight_exit_code)...'

score 4 · Answer 5 · answered May 10 '11 at 08:10

4

You can place an if-statement inside your PS1, which echoes out the exit status only if it is non-zero:

PS1='[\D{%Y-%m-%d} \t] $(es=$?; if [ $es -ne 0 ]; then echo $es; fi) \[\e]0;\u@\h: \w\a\]\$'

answered May 10 '11 at 08:10

dogbane

266,786
75
396
414

1

This is the approach I use, as it allows an `else` clause. Note the importance of copying `$?` to a local variable, as `[` will over-write it before the `echo` is reached. – IMSoP Jun 20 '13 at 15:11

score 4 · Answer 6 · answered Jul 25 '11 at 17:16

4

A common way to do this is to use trap ... ERR to execute arbitrary code when a command fails:

 $ trap 'echo $?' ERR
 $ true
 $ false
1
 $

A classic UNIX practical joke is trap 'echo You have new mail.' ERR

answered Jul 25 '11 at 17:16

Ben Jackson

90,079
9
98
150

score 1 · Answer 7 · answered Oct 16 '13 at 14:24

1

For zsh users: insert this into your PROMPT: %(?,, -%?-)

answered Oct 16 '13 at 14:24

David Faure

1,836
15
19

score 1 · Answer 8 · answered Jul 24 '14 at 19:57

This is the prompt I use, insert into .bashrc and source it to use it. As you can see the PREV_RET_VAL is being appended to PS1 only in the case the value is not 0.

COLOR_RED_BOLD="\[\e[31;1m\]"
COLOR_GREEN_BOLD="\[\e[32;1m\]"
COLOR_NONE="\[\e[0m\]"

# prompt function
promptFunc()
{
PREV_RET_VAL=$?;

PS1=""

PS1="${PS1}\e[1;30m[\e[1;34m\u@\H\e[1;30m:\e[0;37m \e[0;32m\d \T\e[1;30m]\e[1;37m \w\e[0;37m\[\033]0; \w - \u@\H \007\]\n\[\] "

if test $PREV_RET_VAL -eq 0
then
    PS1="${PS1}${COLOR_GREEN_BOLD}\\$ ${COLOR_NONE}"
else
    PS1="${PS1}${COLOR_RED_BOLD}\\$ [${PREV_RET_VAL}] ${COLOR_NONE}"
fi
}

PROMPT_COMMAND=promptFunc

score 1 · Answer 9 · answered Mar 10 '17 at 20:33

Single quote example:

PS1='${?#0}> '

Double quote example (note the extra backslash to escape the $)

PS1="\${?#0}> "

Sample output:

> echo 'ok'
ok
> bogus
bogus: command not found
127>

Explanation: ${var#pattern} is a bash parameter expansion that means remove the shortest matching pattern from the front of $var. So in this case, we are removing 0 from the front of $?, which would effectively truncate an exit code of 0.

If using double quotes, $? would be substituted when PS1 is set, instead of being evaluated each time. Do echo $PS1 to confirm you don't have a hardcoded value in PS1.

Include non-0 exit codes in the subsequent bash prompt

9 Answers9

example when $? is 0:

example when $? is 130: