10 SC2251

Rushen Wang edited this page 2024-09-09 21:44:00 +08:00

Table of Contents

• This ! is not on a condition and skips errexit. Use && exit 1 instead, or make sure $? is checked.
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:
• Related resources:

This ! is not on a condition and skips errexit. Use && exit 1 instead, or make sure $? is checked.

Problematic code:

set -e
! false
rest

Correct code:

set -e
false && exit 1

Rationale:

ShellCheck has found a command inverted with ! that may have no effect. In particular, it does not appear as a condition in an if statement or while loop, or as the final command in a script or function.

The most common reason for this is thinking that it'll trigger set -e aka errexit if a command succeeds, as in the example. This is not the case: ! will inhibit errexit both on success and failure of the inverted command.

Using && exit will instead exit when failure when the command succeeds.

Exceptions:

ShellCheck will not detect cases where $? is implicitly or explicitly used to check the value afterwards:

set -e;
check_success() { [ $? -eq 0 ] || exit 1; }
! false; check_success
! true; check_success

In this case, you can ignore the warning.

Related resources:

• StackOverflow: Why do I need parenthesis In bash set -e and negated return code

ShellCheck

• Installation

  • CentOS6
  • More Installation Guides

• Usage

  • Directive
  • Ignore

• Integrating and extending

  • Misc. contributions
  • Azure Pipelines
  • Buildkite
  • CircleCI
  • DevGuide
  • Integration
  • JUnit
  • Phabricator
  • TravisCI
  • GitLab CI
  • Drone
  • GitHub Actions

• Severity

• Template

Each individual ShellCheck warning has its own wiki page like SC1000. Use GitHub Wiki's "Pages" feature above to find a specific one, or see Checks.