The Linux timeout command and exit codes

Question

In a Linux shell script I would like to use the timeout command to end another command if some time limit is reached. In general:

timeout -s SIGTERM 100 command

But I also want that my shell script exits when the command is failing for some reason. If the command is failing early enough, the time limit will not be reached, and timeout will exit with exit code 0. Thus the error cannot be trapped with trap or set -e, as least I have tried it and it did not work. How can I achieve what I want to do?

Answer 1

Your situation isn't very clear because you haven't included your code in the post.

timeout does exit with the exit code of the command if it finishes before the timeout value.

For example:

timeout 5 ls -l non_existent_file
# outputs ERROR: ls: cannot access non_existent_file: No such file or directory
echo $?
# outputs 2 (which is the exit code of ls)

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From man timeout:

If the command times out, and --preserve-status is not set, then exit with status 124. Otherwise, exit with the status of COMMAND. If no signal is specified, send the TERM signal upon timeout. The TERM signal kills any process that does not block or catch that signal. It may be necessary to use the KILL (9) signal, since this signal cannot be caught, in which case the exit status is 128+9 rather than 124.

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See BashFAQ105 to understand the pitfalls of set -e.