Bash ignoring error for a particular command

问题:

I am using following options

set -o pipefail
set -e

In bash script to stop execution on error. I have 100 of script executing and I don't want to check return code of the script. But for a particular script I want to ignore the error. How can I do that ?

回答1:

The solution:

particular_script || true

Example:

$ cat /tmp/1.sh
particular_script()
{
    false
}

set -e

echo ein
particular_script || true
echo zwei
particular_script
echo drei

$ bash /tmp/1.sh
ein
zwei

drei will be never printed.

Also, I want to add that when pipefail is on, it is enough for shell to think that the entire pipe has non-zero exit code when one of commands in the pipe has non-zero exit code (with pipefail off it must the last one).

$ set -o pipefail
$ false | true ; echo $?
1
$ set +o pipefail
$ false | true ; echo $?
0

回答2:

Just add || true after the command where you want to ignore the error.

回答3:

More concisely:

! particular_script

From the POSIX specification regarding set -e (emphasis mine):

When this option is on, if a simple command fails for any of the reasons listed in Consequences of Shell Errors or returns an exit status value >0, and is not part of the compound list following a while, until, or if keyword, and is not a part of an AND or OR list, and is not a pipeline preceded by the ! reserved word, then the shell shall immediately exit.

回答4:

Just in case if you want your script not to stop if a particular command fails and you also want to save error code of failed command:

code

set -e;
command || EXIT_CODE=$? && true ; 
echo $EXIT_CODE

回答5:

Instead of "returning true", you can also use the "noop" or null utility (as referred in the POSIX specs) : and just "do nothing". You'll save a few letters. :)

#!/usr/bin/env bash
set -e
man nonexistentghing || :
echo "It's ok.."

回答6:

I have been using the snippet below when working with CLI tools and I want to know if some resource exist or not, but I don't care about the output.

if [ -z "$(cat no_exist 2>&1 >/dev/null)" ]; then
    echo "none exist actually exist!"
fi