List of Linux exit status codes

Published:

2024-11-21

Updated:

2024-11-21

Author:

Jonas Jared Jacek

License:

CC BY-SA 4.0

Summary

List of standard and custom Linux exit status codes, numeric values ​​returned by commands or scripts that indicate success, failure, or specific error conditions. Using the correct code provides clarity, consistency, and aids in debugging and automation.

Introduction #

Linux exit status codes are numeric values returned by commands or scripts to indicate the outcome of their execution. A code of 0 signifies success, while non-zero codes represent errors or specific conditions.

Standard codes like 127 (command not found) and custom codes aid in debugging and automation, providing clarity about why a process failed or succeeded.

See the reference lists below to help you chose the correct exit status code for your scripts. Happy hacking.

List of Standard Exit Codes #

List of Custom Exit Codes #

The concept of custom exit codes is not universally defined — developers assign these in their scripts or programs based on the application’s needs.

However, there are some common conventions derived from software like sysexits.h (used in BSD systems) or informal practices across Unix and GNU/Linux. Below I have created an exhaustive list of widely-used custom exit codes along with their typical meanings:

Why Use Exit Codes? #

• Clarity:
  Exit codes make it easier to diagnose issues when a script fails.
• Consistency:
  Following conventions like sysexits.h helps align your scripts with broader industry practices.
• Error Handling:
  They enable precise handling of different error scenarios in automation tools or other scripts.

Usage Tips #

Check Exit Codes #

After running a command, check its exit stautus code with:

echo $?

Handle Custom Codes in Scripts #

Use case statements to act on specific, custom exit codes:

my_command
case $? in
    0) echo "Success!";;
    1) echo "General error occurred.";;
    127) echo "Command not found.";;
    *) echo "Unhandled exit code.";;
esac

Define Exit Codes for Scripts #

In custom scripts, define meaningful exit codes to signal specific issues:

EX_USAGE=64
EX_FILE_NOT_FOUND=66
EX_SUCCESS=0

if [ ! -f "$1" ]; then
  echo "File not found!"
  exit $EX_FILE_NOT_FOUND
fi

Simplify Checks with && and || #

Use && to run a command only if the previous command succeeds and || to handle failures:

command && echo "Success" || echo "Failure"

Use exit to Stop Script Execution #

Exit immediately with a meaningful status if an error is detected:

if [ -z "$variable" ]; then
  echo "Error: Variable is unset!"
  exit 1
fi

Use trap for Cleanup on Error #

Ensure resources (e.g., temp files) are cleaned up, even if a script exits prematurely:

trap 'rm -f /tmp/myfile; exit' INT TERM EXIT
command || exit 1

Check Exit Status in Loops #

Handle failures within loops:

for file in *.txt; do
  process "$file"
  if [ $? -ne 0 ]; then
    echo "Error processing $file"
    exit 1
  fi
done

Avoid Confusion with Signal Numbers #

Exit codes >128 usually represent signals (128 + signal number), e.g., 130 means the script was terminated by SIGINT.

Combine set Options for Robust Scripts #

Enable stricter error handling with set options:

• set -e: Exit on any error.
• set -u: Treat undefined variables as errors.
• set -o pipefail: Detect errors in pipelines.

Further readings #

Sources and recommended, further resources on the topic:

• FreeBSD sysexits Manual Page
• GNU manual - Exit Status

Author

Jonas Jared Jacek (J15k)

Jonas works as project manager, web designer, and web developer since 2001. On top of that, he is a Linux system administrator with a broad interest in things related to programming, architecture, and design. See: https://www.j15k.com/

<p xmlns:cc="http://creativecommons.org/ns#" xmlns:dct="http://purl.org/dc/terms/"><a property="dct:title" rel="cc:attributionURL" href="https://www.ditig.com/publications/linux-exit-status-codes">List of Linux exit status codes</a> by <a rel="cc:attributionURL dct:creator" property="cc:attributionName" href="https://www.j15k.com/">Jonas Jared Jacek</a> is licensed under <a href="https://creativecommons.org/licenses/by-sa/4.0/" target="_blank" rel="license noopener noreferrer">CC BY-SA 4.0</a>.</p>