From 6f48846cc453b15face8c095727a7f25496619d6 Mon Sep 17 00:00:00 2001
From: Xiang ZHU <xiang.zhu@outlook.com>
Date: Wed, 8 Nov 2023 23:55:50 +0100
Subject: [PATCH] new post 2023-11-08-github-actions-bash-shell-pipefail.md

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+---
+last_modified_at:
+title: "Github Actions - Bash shell -e -o pipefail"
+excerpt: ""
+tags:
+  - cicd
+  - githubaction
+  - shell
+published: true
+# header:
+#   teaserlogo:
+#   teaser: ''
+#   image: ''
+#   caption:
+gallery:
+  - image_path: ''
+    url: ''
+    title: ''
+---
+
+Bash shell in Github actions by default is run with `-e -o pipefail` option. The full command used by Github actions is :
+
+```bash
+shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
+```
+
+`-o pipefail` means that if any command in a pipeline fails, that return code will be used as the return code of the whole pipeline. And due to `-e` option, this makes the shell exit immediately if a command within the script exits with a non-zero status (i.e., fails). This is a good thing, but it can be a problem if you want to ignore the return code of a command in a pipeline. And especially in Github Actions output, you cannot see the error message of the command that failed. Github Actions just shows a generic error message: "**Error: Process completed with exit code 1.**", which makes it hard to debug.
+
+For example, following command:
+
+- will **success** even `grep` does not find anything in a standard bash shell (your local VM for example)
+- but will **fail** in Github actions bash shell with the error message "**Error: Process completed with exit code 1.**".
+
+```bash
+echo "hello world" | grep "foo" | wc -l
+```
+
+If you do not care about the grep result, to bypass this, you can use `|| true` at the end of the `grep` command. This will make sure that the return code of the grep command is always 0.
+
+```bash
+echo "hello world" | { grep "foo" || true ; } | wc -l
+```
+
+To verify current bash shell options, you can use `set -o` command:
+
+```bash
+set -o
+# or
+
+$ set -o | grep -E "errexit|pipefail"
+errexit         off
+pipefail        off
+```