Metadata

ID: bash-code-quality/deprecated-bracket-arithmetic

Language: Bash

Severity: Warning

Category: Code Style

Description

The $[expression] form is an old Bash arithmetic expansion. It was never documented in POSIX, and Bash 5.2 removed support for it without a clear parse error in all cases, so scripts can fail silently on newer systems.

Use the standard $((expression)) form instead, which is widely supported and portable.

Non-Compliant Code Examples

#!/bin/bash
echo "$[1 + 1]"
y=$[2 * 3]

Compliant Code Examples

#!/bin/bash
echo "$((1 + 1))"
x=$((a * 2))
y=$(( (3 + 4) ))

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