1 SC2324

Vidar Holen edited this page 2023-07-30 16:06:16 -07:00

Table of Contents

• var+=1 will append, not increment. Use (( var += 1 )), declare -i var, or quote number to silence.
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:
• Related resources:

var+=1 will append, not increment. Use (( var += 1 )), declare -i var, or quote number to silence.

Problematic code:

var=2 n=3
var+=$n

Correct code:

In bash/ksh, use an (( arithmetic context ))

(( var += n ))

or declare the variable as an integer type:

declare -i var=2
n=4
var+=$n

For POSIX sh, use an $((arithmetic expansion)):

var=$((var+n))

Rationale:

The problematic code attempts to add 2 and 3 to get 5.

Instead, += on a string variable will concatenate, so the result is 23.

Exceptions:

If you do want to concatenate a number, for example to append trailing zeroes, you can silence the warning by quoting the number:

var+="000"

Related resources:

• Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!

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.