main exit/return

[Rahul]

Hi Everyone,

I have seen code in different styles like

main(argc,argv)
int argc;
char **argv;
{
if(argc != 2) exit(1);
else exit(0);
}

int
main(argc,argv)
int argc;
char **argv;
{
if(argc != 2) return(-1);
else return(0);
}

I'm not sure as to which version is advised by the standard and the
reason to avoid the other approach. What does the standard recommend
in case of main() function?

Thanks in advance ! ! !

[Chris Dollin]

Chris Torek wrote:

>>On Jun 3, 10:46 am, Chris Dollin <chris.dol...@h p.comwrote:
The same values apply to the argument of `exit`, but why use
`exit` when you're in `main`?

>>christian.b au wrote:

>>There is a subtle difference if you used atexit () to register
functions that will be called when the program exits: If you call exit
() from main, local variables of the main function will still exist
when these functions execute; if you use a return statement then local
variables of main are gone.

In article <g2*********@ne ws-pa1.hpl.hp.com>
Chris Dollin <ch**********@h p.comwrote:

>>That's a nice [1] gotcha; I hadn't thought of that. I'm trying to
think of a natural example where it would matter ...

[1] As in "oh noes, my brain just melted".

The classic example problem is:

#include <stdio.h>

int main(void) {
char buf[BUFSIZ];

setbuf(stdout, buf);
... do some work ...
return 0;
}

Thanks, Chris; I don't use setbuf often enough to have thought of that ...

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[Chris Dollin]

Richard Heathfield wrote:

Keith Thompson said:

>santosh <sa*********@gm ail.comwrites:

<snip>

>>Maybe one should use return when main has been called recursively and
exit() for a normal termination of main?

Maybe one shouldn't call main recursively. You can always write a
recursive function and call it from main.

Recursive main is one of those techniques that every C programmer should
use occasionally. It's like int delete, or struct T *new, or x =
a//*divide a by b */b, and so on. I'm not saying you should do it too
much, mind you - just... um... now and again.

And you can stop whenever you want?

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registered office: Cain Road, Bracknell, Berks RG12 1HN 690597 England