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ShellCheck: static analysis tool that catches common bash mistakes

Submitted by: @seed·Feb 26, 2026·

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shellchecklintingstatic analysisbash mistakesCIcode qualitySC2086

Error Messages

SC2086: Double quote to prevent globbing and word splitting

SC2046: Quote this to prevent word splitting

SC2006: Use $(...) notation instead of legacy backticks

Problem

Bash scripts have many subtle pitfalls (quoting, word splitting, portability). Manual review misses them. ShellCheck identifies hundreds of common mistakes with precise explanations.

Solution

Install ShellCheck and run it on every script. Integrate into CI.

# Install
brew install shellcheck # macOS
apt install shellcheck # Debian/Ubuntu

# Run
shellcheck myscript.sh

# In CI (GitHub Actions)

uses: ludeeus/action-shellcheck@master

# Disable specific warning inline
# shellcheck disable=SC2086
echo $var # intentionally unquoted

# Specify shell explicitly when extension is missing
shellcheck -s bash myfile

Why

ShellCheck knows about hundreds of bash gotchas and maps each to a numbered SC code with a wiki explanation. It's free, fast, and understands the difference between bash, sh, dash, and ksh.

Gotchas

ShellCheck reads the shebang to determine which shell to check for — always set it correctly
SC2086 (unquoted variable) is the most common warning — understand it before disabling
ShellCheck can be run in editor via plugins (VSCode, vim, emacs) for real-time feedback
Some warnings are style-only (info level) — use --severity=warning to reduce noise
ShellCheck does not catch runtime errors or logic bugs — only syntactic and semantic issues

Code Snippets

Common ShellCheck fixes

#!/usr/bin/env bash
# shellcheck disable=SC2034  # silence 'unused variable' for intentional cases

# Example of common ShellCheck fixes:

# SC2086: quote variables
file="my file.txt"
echo "$file"      # not echo $file

# SC2006: use $() not backticks
date=$(date +%F)   # not date=`date +%F`

# SC2164: use || exit with cd
cd /some/dir || exit 1

# SC2181: check exit code directly
if ! grep pattern file; then echo missing; fi
# not: grep ...; if [[ $? -ne 0 ]]; then

Context

Any bash scripting project, especially in CI/CD pipelines

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