\n
Here, if [ $? -ne 0 ]<\/code> checks the exit status of the recently executed ls<\/strong> command. If the exit status is not equal to zero, the script exits using exit 1<\/code> without checking the further command.<\/p>\n<\/div><\/div>\n![\"Exit](\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2024\/02\/Exit-script-using-exit-command-with-exit-code-if-command-fails.png\")
<\/p>\n
As you can see from the image the ls<\/strong> command failed and so the script exits immediately without even executing the next command.<\/p>\n<\/span>2. Using \u201cset -e\u201d Option<\/span><\/h3>\nThe set -e<\/code>\u00a0option instructs a Bash script to terminate as soon as a command fails, i.e., returns a non-zero exit status.<\/p>\nTo check how to exit if a command fails using set -e<\/strong> option, check out the following Bash script:<\/p>\n#!\/bin\/bash\n\nset -e\n\nmkdir \/home\/example.txt<\/code><\/pre>\n EXPLANATION<\/div>
\n
Here, set -e<\/code> ensures that the script exits immediately if the mkdir<\/strong> command fails to execute.<\/p>\n<\/div><\/div>\n![\"Exit](\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2024\/02\/Exit-script-using-set-e-option-if-command-fails.png\")
<\/p>\n
This images states that the mkdir<\/strong> command failed to create the directory ‘example.txt’ which leads the script to exit immediately.<\/p>\n<\/span>3. Using \u201cset -eo pipefail\u201d Option<\/span><\/h3>\nWhen a script contains multiple commands using piped statements, the set -eo pipefail<\/code> option helps the script to exit if any command in the pipeline fails, not just the most recent one.<\/p>\nFollowing is a Bash script that exits using set -eo pipefail<\/strong> option when a command fails:<\/p>\n#!\/bin\/bash\n\nset -eo pipefail\n\necho "The command runs"\n#'find' command: Generates a list of files in \/path\/to\/directory (including hidden ones)\n#'sort' command: Sorts the list of files in reverse order\n#'grep' command: Filters out lines that contain the word "Linux"\nfind \/home\/nadiba\/distro -type f | sort -r | grep -v "Linux"\necho "The command doesn't run"<\/code><\/pre>\n EXPLANATION<\/div>
\n
Here, The set -eo pipefail<\/code> ensures that the script exits as soon as any command either \u201cfind\u201d, \u201csort\u201d or \u201cgrep\u201d inside the pipeline fails.<\/p>\n<\/div><\/div>\n![\"Exit](\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2024\/02\/Exit-script-using-set-eo-pipefail-option-if-a-command-fails.png\")
<\/p>\n
In the above image, you can see that the find<\/strong> command failed to list the files in ‘\/home\/nadiba\/distro’ which causes the script to exit immediately without even executing the last echo<\/strong> command.<\/p>\n<\/span>4. Using \u2018set -u\u2019 Option<\/span><\/h3>\nThe set -u<\/code> option is generally used at the start of a script where the -u<\/code> option stands for nounset<\/strong>. When enabled, the “set -u” option terminates the script if there is any undefined or uninitialized variable.<\/p>\nHere\u2019s a Bash script showing how to exit using set -u<\/strong> when a command fails:<\/p>\n#!\/bin\/bash\n\n#nounset\nset -u\n\necho "The command runs"\necho $non_existing_variable\necho "The command doesn't run"<\/code><\/pre>\n EXPLANATION<\/div>
\n
Here, set -u<\/code> treats the unset or uninitialized variable $non_existing_variable<\/strong> as an error and causes the script to exit immediately.<\/p>\n<\/div><\/div>\n![\"Exit](\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2024\/02\/Exit-script-using-set-u-option-when-found-an-uninitialized-variable.png\")
<\/p>\n
From the image, you can see that the script referenced the unset variable as an unbound variable<\/strong> error which instructs the script to exit immediately.<\/p>\n<\/span>Conclusion<\/span><\/h2>\nSo far, this article described different methods to check if a command fails or succeeds in Bash as well as to exit if a command fails in Bash. To conclude, having a good knowledge of these methods ensures the reliability and robustness of Bash scripts. In fact, verifying the exit status of a command really helps in error handling and automating tasks based on different command executions.<\/span><\/p>\n<\/span>People Also Ask<\/span><\/h2>\n<\/span>How to check if a command fails in Bash?<\/span><\/h3>\nTo check if a command fails in Bash, use the special variable $?<\/code> inside conditional statements. To do this, use the if [ $? -ne 0 ]<\/code> syntax to check if the exit status of the command is not equal to zero. Usually, a command that fails to execute will return a non-zero output. If the condition is true, it means that the command failed to execute.<\/p>\n<\/span>How to check if a Bash command succeeds?<\/span><\/h3>\nTo check if a Bash command succeeds, use the syntax if [ $? -eq 0 ]<\/code> that determines if the exit status of the command is equal to zero. A successful execution always returns a zero exit status. So, if the condition evaluates to true, it indicates the command executed successfully.<\/span><\/p>\n<\/span>Can I immediately exit a script if any command fails in bash?<\/span><\/h3>\nYes<\/b>, you can immediately exit a script if any command fails in Bash by enabling the set -e<\/code> option at the start of the script. The ‘set -e’ option enables the <\/span>errexit <\/b>mode, which instructs the Bash script to terminate immediately when a command exits with a non-zero exit status i.e. fails or an error occurs.<\/span><\/p>\n<\/span>Does a Bash script fail if a command fails?<\/span><\/h3>\nNo<\/strong>, by default a Bash script does not fail if a command fails. It continues executing subsequent commands without caring about earlier commands unless you set or enable certain options.<\/p>\n<\/span>How to exit 1 if command fails in Bash?<\/span><\/h3>\nTo exit 1 if command fails in Bash, first explicitly check the exit status of the command using $?<\/code> variable and then use the exit<\/code> command with the exit code 1<\/strong> if the command fails. For example:<\/p>\n#!\/bin\/bash\n\n#Command1\nls -l \/path\/to\/directory\nif [ $? -ne 0 ]; then\n\u00a0\u00a0\u00a0 echo "ls command failed. Exit the script"\n\u00a0\u00a0\u00a0 exit 1\nfi\n\n#Command2\nmkdir \/path\/to\/directory\nif [ $? -ne 0 ]; then\n\u00a0\u00a0\u00a0 echo "mkdir command failed. Exit the script"\n\u00a0\u00a0\u00a0 exit 1\nfi<\/code><\/pre>\n<\/span>Can I check the exit status of a command in a function?<\/span><\/h3>\n