C exit() function

Last update on December 29 2022 12:52:23 (UTC/GMT +8 hours)

C exit() function - Terminate a process

The exit() function is used to return control to the host environment from the program.

Syntax exit() function

void exit(int status)

Parameters exit() function

Name	Description	Required /Optional
status	Exit status code.	Required

Return value from exit()

This function does not return any value.

Example - 1: exit() function

The following example shows the usage of exit() function.

#include <stdio.h>
#include <stdlib.h>
 
FILE *stream;
 
int main(void)
{
  printf("Exit when i = 7");
  for(int i =0; i<=10; i++)
  {
  	printf("\ni = %d",i);
       if (i ==7)
	   exit(1);
   }
}

Output:

Exit when i = 7
i = 0
i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7

Example - 2: exit() function

In this example, the program ends after deleting buffers and closing any open files if it is unable to open the file 'test.txt'.

#include <stdio.h>
#include <stdlib.h>
 
FILE *stream;
 
int main(void)
{
   if ((stream = fopen("user/test.txt", "r")) == NULL)
   {
      perror("Could not open data file! ");
      exit(EXIT_FAILURE);
   }
}

Output:

Could not open data file! : No such file or directory

C Programming Code Editor:

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C Programming: Tips of the Day

Returning an array using C

You can't return arrays from functions in C. You also can't (shouldn't) do this:

char *returnArray(char array []){
 char returned [10];
 //methods to pull values from array, interpret them, and then create new array
 return &(returned[0]); //is this correct?
}

returned is created with automatic storage duration and references to it will become invalid once it leaves its declaring scope, i.e., when the function returns.

You will need to dynamically allocate the memory inside of the function or fill a preallocated buffer provided by the caller.

Dynamically allocate the memory inside of the function (caller responsible for deallocating ret)

char *foo(int count) {
    char *ret = malloc(count);
    if(!ret)
        return NULL;

    for(int i = 0; i < count; ++i) 
        ret[i] = i;

    return ret;
}

Call it like so:

int main() {
    char *p = foo(10);
    if(p) {
        // do stuff with p
        free(p);
    }

    return 0;
}

Ref : https://bit.ly/3yFIeao

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