Which exit status should a deployment‑check script treat as success when grep finds no matches?

Goal

Diagnose a failed deployment by inspecting application logs with a Bash script that uses grep and head pipelines.

Constraints

The script runs with set -e and set -o pipefail to abort on errors, but grep returns 1 when no lines match, 2 on file errors, and 141 when terminated by SIGPIPE from head. These statuses are not automatically distinguishable by default.

Unresolved Decision

When the log contains no error lines, should the script consider grep’s exit 1 as a successful “no errors found” state, or as a distinct “log inconclusive” condition that warrants further investigation?

Specific Questions

• Should the script treat grep exit 1 as a success or as an inconclusive state when set -e and pipefail are enabled?
• How can a Bash script reliably differentiate between grep exit 1 (no match), exit 2 (file error), and the 141 SIGPIPE status produced by head in a pipeline?
• What best‑practice pattern should be used to combine grep and head in a diagnostic pipeline while preserving the correct exit status for each failure mode?