Thread: How to give an "emergency exit" to my program?

Use the return statement to leave a function, this is the graceful way.

Use the exit() call to exit your program, but this isn't graceful.

Code:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    FILE *fp;
    
    if ((fp = fopen("file.txt", "r")) == NULL)
    {
        perror("file.txt");
        return (EXIT_FAILURE);
    }
    printf ("File opened successfully\n");
    
    fclose(fp);
    
    return (EXIT_SUCCESS);
}

If you're going to return from a function, make sure you return something that denotes the failure. Likes this:

Code:

#include <stdio.h>
#include <stdlib.h>

int DoIt(FILE *fp);

int main(void)
{
    FILE *fp;
    
    if ((fp = fopen("file.txt", "r")) == NULL)
    {
        perror("file.txt");
        return (EXIT_FAILURE);
    }
    printf ("File opened successfully\n");
    
    if (DoIt(fp) < 0)
        printf ("Error in function do it\n");
        
    fclose(fp);
    
    return (EXIT_SUCCESS);
}

int DoIt(FILE *fp)
{
    char buf[BUFSIZ];
    if (fgets(buf, sizeof buf, fp) == NULL)
        return -1;

    printf ("buf is %s", buf);
    
    return 0;
}

Another way to have your program terminate immediately is to use uninitialized pointers. Something like:

Code:

void terminate( void )
{
    char **quit;
    int x;
    for( x = 0; x < 10000; x++ )
        strcpy( quit[x], "quit now please" );
}

...will usually do the trick for you.

Quzah.

Here's a controlled way to run out of memory. I haven't run it in full, but it should work.

Code:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    char *p = NULL, *tmp;
    long int l = 0;
    
    while ((tmp = realloc(p, 4096)) != NULL)
    {
        p = tmp;
        l++;
    }
    
    printf ("We ran out of memory after %ld loops\n", l);
    
    free(p);
    
    return (EXIT_SUCCESS);
}

Here's a controlled way to run out of memory. I haven't run it in full, but it should work.

I wasn't trying to run out of memory, only showing how to make your program perform an "emergency exit".

Actually, depending on what OS you're running, I don't think your program will actually run out of memory--or at least, it won't untill your hard drive is full!

I remember running something similar before in ... WinME? Win98? Something. ... and it just kept filling my hard drive. Kinda nifty.

Quzah.

>>>I wasn't trying to run out of memory
Yeah, I could see what you were doing I was (kind of) answering the question in the previous post.

>>>Kinda nifty.
That made me laugh!