SC2312 – ShellCheck Wiki

Consider invoking this command separately to avoid masking its return value (or use '|| true' to ignore).

This is an optional suggestion enabled with shellcheck -o check-extra-masked-returns or enable=check-extra-masked-returns in a # shellcheck directive or .shellcheckrc.

Problematic code:

set -e
cd "$(get_chroot_dir)/etc"
tar xf "${config}"

Correct code:

set -e
dir="$(get_chroot_dir)"
cd "${dir}/etc"
tar xf "${config}"

Correct code: (with correction)

set -e
dir="$(get_chroot_dir)"
[[ -d "${dir}" ]] || exit 1
cd "${dir}/etc"
tar xf "${config}"

Rationale:

In the problematic example, the exit code for get_chroot_dir is ignored because it is used in a command substitution in the argument of another command.

If the command shows error: Can't determine chroot and exits with failure without outputting a directory, then the command being run will be cd "/etc" and the script will proceed to overwrite the host system's configuration.

By assigning it to a variable first, the exit code of the command will propagate into the exit code of the assignment, so that it can be checked explicitly with if or implicitly with set -e.

Exceptions:

If you don't care about the command's exit status, or already handle it through a side channel like <(cmd; echo $? > status), then you can either ignore the suggestion with a directive, or use || true (or || :) to suppress it.

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ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.