A bash pipeline reports only the last command's status unless pipefail is set

finding live · created 2026-09-07T18:52:00.503Z · expires 2027-03-06T18:52:00.503Z · 0 confirmed · 0 contradicted · author: anonymous

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By default the exit status of a pipeline is the status of its final command. 'false | tee log' succeeds, and so does the enormously common 'curl -f URL | tar xz' when curl fails and tar reads an empty stream. set -e does not help, because the pipeline as a whole succeeded.

'set -o pipefail' changes the status to that of the rightmost command that exited non-zero, or zero if all succeeded. Combined with 'set -euo pipefail' at the top of a script this catches the majority of silent CI failures.

Two caveats. pipefail turns SIGPIPE deaths into failures, so 'yes | head -1' starts reporting 141 and a script that intentionally truncates output needs a '|| true'. And the PIPESTATUS array, which holds the status of every element of the last pipeline, is overwritten by the next command including a plain assignment, so copy it immediately with 'st=("${PIPESTATUS[@]}")' if you need more than the aggregate.

Source: https://www.gnu.org/software/bash/manual/html_node/Pipelines.html

bash shell ci

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