Boost Your Shell Scripts with ShellCheck: Install, Use, and Real‑World Examples

What is ShellCheck?

ShellCheck is a static analysis tool for shell scripts (bash, dash, zsh, etc.). It parses a script, reports syntax errors, potential runtime problems (e.g., unquoted variables, word‑splitting, globbing), and offers style and best‑practice recommendations.

Key Features

Error detection : syntax mistakes, undefined variables, misuse of test operators, I/O errors.

Style suggestions : consistent indentation, quoting, and command usage.

Best‑practice advice : safer constructs, avoidance of deprecated features.

Cross‑platform : runs on Linux, macOS, Windows.

Custom rules : users can add project‑specific checks.

Editor integration : supports Vim, Emacs, Sublime, Atom, VSCode and other IDEs.

Installation

RHEL / CentOS / Fedora

yum -y install epel-release   # enable EPEL repository
yum install ShellCheck -y    # install ShellCheck

Debian / Ubuntu

sudo apt install shellcheck   # install ShellCheck

Online usage

ShellCheck can be run in a browser at https://www.shellcheck.net by pasting the script into the web interface.

Basic Usage

Run ShellCheck from the command line, passing the script file name: shellcheck test.sh The tool prints warnings with line numbers and suggested fixes.

Practical Example

Original script example.sh:

#!/bin/bash

echo "Hello, $1"

if [ $1 = "World" ]; then
    echo "You said hello to World!"
fi

Running shellcheck example.sh yields:

In example.sh line 4:
    if [ $1 = "World" ]; then
       ^-- SC2086: Double quote to prevent globbing and word splitting.

The warning indicates that $1 is not quoted, which can cause word‑splitting or globbing. The corrected script is:

#!/bin/bash

echo "Hello, $1"

if [ "$1" = "World" ]; then
    echo "You said hello to World!"
fi

Quoting the variable makes the script robust against spaces or special characters in the argument.

Editor Integration (VSCode)

Open the Extensions view (Ctrl+Shift+X).

Search for shellcheck and install the “ShellCheck for Visual Studio Code” extension.

Reload or restart VSCode.

Open a shell script file; VSCode runs ShellCheck automatically and shows warnings inline.

Repository

GitHub:

https://github.com/koalaman/shellcheck