2 SC2292

Grische edited this page 2021-11-11 14:42:32 +01:00

Table of Contents

• Prefer [[ ]] over [ ] for tests in Bash/Ksh.
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:
• Related resources:

Prefer [[ ]] over [ ] for tests in Bash/Ksh.

This is an optional suggestion. It must be explicitly enabled with a directive enable=require-double-brackets in a # shellcheck comment or .shellcheckrc

Problematic code:

[ -e /etc/issue ] 

Correct code:

[[ -e /etc/issue ]]

Rationale:

ShellCheck has been explicitly asked to warn about uses of [ .. ] in favor of the extended Bash/Ksh test [[ .. ]].

[[ .. ]] suppresses word splitting and globbing, supports a wider variety of tests, and is generally safer and better defined than [ .. ]. For an in-depth list of differences, see the Related Resources.

Exceptions:

This check is not enabled by default, and may have been turned on for your current project by someone who wants it enforced. You can still ignore it with a directive.

This suggestion does not trigger for Sh or Dash scripts, even when explicitly enabled, as these shells don't support [[ .. ]].

Related resources:

• BashFAQ 031: What is the difference between test, [ and [[ ?

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