Question

I understand that exit(1) indicated an error , for example :

if (something went wrong) 

     exit(EXIT_FAILURE);

But what’s the purpose of using exit(EXIT_SUCCESS); ?

When handling with processes maybe ? e.g. for fork() ?

thanks

Answer 1

This gives the part of the system that invokes the program (usually the command shell) a way to check if the program terminated normally or not.

Edit – start –

By the way, it is possible to query the exit code of an interactive command as well through the use of the $? shell variable. For instance this failed ls command yields an exit code of value 2.

$ ls -3
ls: invalid option -- '3'
Try `ls --help' for more information.
$ echo $?
2

Edit – end –

Imagine a batch file (or shell script) that invokes a series of programs and depending on the outcome of each run may choose some action or the other. This action may consist of a simple message to the user, or the invocation of some other program or set of programs.

This is a way for a program to return a status of its run.

Also, note that zero denotes no problem, any non-zero value indicates a problem.

Programs will often use different non-zero values to pass more information back (other than just non-normal termination). So the non-zero exit value then serves as a more specific error code that can identify a particular problem. This of course depends on the meanings of the code being available (usually/hopefully in the documentation)

For instance, the ls man page has this bit of information at the bottom:

Exit status is 0 if OK, 1 if minor problems, 2 if serious trouble.

For Unix/Linux man pages, look for the section titled EXIT STATUS to get this information.