Bourne Shell Exit Status Examples For Linux and Unix

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The Bourne shell is the default shell for many Linux and Unix systems, and it provides a way to check the exit status of a command or a script. The exit status is a numerical value that represents the success or failure of the command or script. A value of 0 represents success, while any other value represents failure. Here are some examples of Bourne shell exit status codes:

  1. Successful command: If a command runs successfully, it returns an exit status of 0. For example, the following command returns a success exit status:
    ls /home
  2. Unsuccessful command: If a command fails, it returns a non-zero exit status. The specific value depends on the type of error. For example, the following command returns a non-zero exit status:
    ls /this/directory/does/not/exist
  3. Testing exit status: You can use the echo command and the special variable $? to display the exit status of the last command. For example:
    ls /home
    echo $?

    This will output 0 to indicate that the ls command was successful. Alternatively, if you run:

    ls /this/directory/does/not/exist
    echo $?

    This will output a non-zero value (usually 1) to indicate that the ls command failed.

  4. Checking exit status in a script: You can use exit statuses to control the behavior of a script. For example, you can check whether a command ran successfully and take different actions based on the result. Here’s an example:
    #!/bin/sh

    rm /tmp/file.txt
    if [ $? -eq 0 ]; then
    echo "File deleted successfully"
    else
    echo "Failed to delete file"
    fi

    In this example, the rm command is executed to delete a file. If the command runs successfully, the script will print “File deleted successfully”. If it fails, the script will print “Failed to delete file”. The $? variable is used to check the exit status of the previous command (in this case, rm).

These are just a few examples of how you can use exit statuses in the Bourne shell. By checking the exit status of commands, you can automate scripts and make them more robust.

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