Re: pipes that write to a file

[Philip Rowlands]

On Sun, 27 Jun 2021, at 01:13, Bruno Haible wrote:

> So, people come to recommend the 'sponge' program from moreutils [2]:
> 
>    prog1 < FILE | prog2 | prog3 | sponge FILE
> 
> But this program has the drawback that, requiring another step in the
> pipeline, the exit code of the previous command gets lost.

To this specific point, there are bash options (not sure about other shells)

Option 1:

bash provides PIPESTATUS as an array of exit codes.

$ seq 50 | grep apple | wc -l
0

$ echo ${PIPESTATUS[*]}
0 1 0

Option 2:

bash provides the "pipefail" to expose a non-zero exit status from mid-pipeline.

$ set -o pipefail

$ seq 50 | grep apple | wc -l
0

$ echo $?
1



Cheers,
Phil