Bash & (ampersand) operator

Question

I'm trying to run 3 commands in parallel in bash shell:

$ (first command) & (second command) & (third command) & wait

The problem with this is that if first command fails, for example, the exit code is 0 (I guess because wait succeeds).

The desired behavior is that if one of the commands fails, the exit code will be non-zero (and ideally, the other running commands will be stopped).

How could I achieve this?

Please note that I want to run the commands in parallel!

Answer 1

You should use && instead of &. eg:

first command && second command && third command && wait

However this will NOT run your command in parallel as every subsequent command's execution will depend on exit code 0 of the previous command.

Answer 2

the best I can think of is:

first & p1=$!
second & p2=$!
...

wait $p1 && wait $p2 && ..

or

wait $p1 || ( kill $p2 $p3 && exit 1 )
...

however this still enforces an order for the check of processes, so if the third fails immediately you won't notice it until the first and second finishes.

Answer 3

This might work for you:

parallel -j3 --halt 2 <list_of_commands.txt

This will run 3 commands in parallel.

If any running job fails it will kill the remaining running jobs and then stop, returning the exit code of the failing job.