return codes in c

exvor · 01-21-2005, 03:35 PM

Ok im just begining c programming and i got a question.

Whats with return codes in main?

i understand that when you return something to the calling program like in a custom function you can return values

but what is the use for return 1 if something in main failes.

nothing ever reads main's return code. Is it a usefull thing to do or is it just used for clarity in C programming, or perhaps it was used at some time by a now extint os ?

Tinkster · 01-21-2005, 03:41 PM

That's so the OS can use it in a script, for instance.

Cheers,
Tink

aluser · 01-21-2005, 03:45 PM

To elaborate:

Code:

16:42 aluser@alf:~/C$ cat > test.c
int main() {
  return 42;
}
16:43 aluser@alf:~/C$ gcc -o test test.c
16:43 aluser@alf:~/C$ ./test
16:43 aluser@alf:~/C$ echo $?
42

If you want the really gory details, a process gets information about one of its children's exit status via wait() or waitpid(). Type man 2 wait for how to use those syscalls.

exvor · 01-21-2005, 03:49 PM

Yea I could see how that would be benifical in linux in a shell script. You could test the value of the program to see if it was sucessfull or not.

I guess in windows it would be useless unless you were in effect using it in the same manner in a batch file. But a standalone program would have no use for it.

In my programing im trying not to side with either camp (windows / linux) i really started out learning just for linux but if i ever want to use this skill in a company enviorment Im gonna have to learn how to program in C for windows.

:P in either effect it should be interesting. I sure get a chukkle every time i crash CMD in windows xp when linux just give me a nice simple error "segmentaion fault"

tamoneya · 01-21-2005, 08:45 PM

I am not that familiar with C but it is similar to java in many ways. If you really have aproblem with returning 1 then you can make main return void.