Question

6

Is it preferred to avoid use of "exit" in bash scripts as much as possible?

rated 0 times [ 6] [ 0] / answers: 1 / hits: 9916 / 2 Years ago, sun, july 31, 2022, 6:38:38

I've been told in php it's preferred to avoid the use of the exit command as much as possible.

Is the same true for bash?

For example is the following

#!/bin/bash

if [ -z $1 ]; then

        echo You need to enter the directory you want to backup

else

        sourceFile=$1

        targetFile=/home/me/Desktop/myBackups/files_$(date +%Y_%m_%d_%s)

        tar cvf $targetFile $sourceFile

fi

Preferred to this?

#!/bin/bash

if [ -z $1 ]; then

        echo You need to enter the directory you want to backup

        exit

fi

        sourceFile=$1

        targetFile=/home/me/Desktop/myBackups/files_$(date +%Y_%m_%d_%s)

        tar cvf $targetFile $sourceFile

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4 Years ago

answered 2 Years ago tusmuumu · Accepted Answer

Quoting 'Code Complete'

Use [exit] when it enhances readability In certain routines, once
you know the answer, you want to [exit] to the calling routine
immediately. If the routine is defined in such a way that it doesn’t
require any further cleanup once it detects an error, not [exiting]
immediately means that you have to write more code.

So normally one exit is preferred (people looking at your code don't have to find the correct exit statement), however with error checking (especially at the start of a program/routine having multiple exit statements is clearer.

Your example is borderline, however I would say that the second is preferred so that maintenance to your program/script can leave it tidy.

Your program currently is (in psudocode)

if error condition 1

    // Show error message 1

else

    // Do stuff

fi

or

if error condition 1

    // Show error message 1

    // exit

fi



// Do stuff

Once your program has grown, you realise some more ways that the program can fail. Your program now becomes

if error condition 1

    // Show error message 1

else 

    if error condition 2

         // Show error message 2

    else

         if error condition 3

             // Show error message 3

         else

             // Do stuff

         fi

    fi

fi

or maybe

if error condition 1

    // Show error message 1

else if error condition 2

    // Show error message 2

else if error condition 3

    // Show error message 3

else

    // Do stuff

fi

versus

if error condition 1

    // Show error message 1

    // exit

else if error condition 2

    // Show error message 2

    // exit

else if error condition 3

    // Show error message 3

    // exit

fi



// Do stuff

In my mind, the last one is the clearest in being able to spot which is the error cases and which is the main flow of the program. Now add returning different values (eg. 0 on success, 1 on error 1, 2 on error 2, etc.) and the difference will become more pronounced.