C library function - qsort()

Description

The C library function void qsort(void *base, size_t nitems, size_t size, int (*compar)(const void *, const void*)) sorts an array.

Declaration

Following is the declaration for qsort() function.

void qsort(void *base, size_t nitems, size_t size, int (*compar)(const void *, const void*))

Parameters

• base -- This is the pointer to the first element of the array to be sorted.

• nitems -- This is the number of elements in the array pointed by base.

• size -- This is the size in bytes of each element in the array.

• compar -- This is the function that compares two elements.

Return Value

This function does not return any value.

Example

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

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

int values[] = { 88, 56, 100, 2, 25 };

int cmpfunc (const void * a, const void * b)
{
   return ( *(int*)a - *(int*)b );
}

int main()
{
   int n;

   printf("Before sorting the list is: \n");
   for( n = 0 ; n < 5; n++ ) {
      printf("%d ", values[n]);
   }

   qsort(values, 5, sizeof(int), cmpfunc);

   printf("\nAfter sorting the list is: \n");
   for( n = 0 ; n < 5; n++ ) {
      printf("%d ", values[n]);
   }
  
  return(0);
}

Let us compile and run the above program, this will produce the following result:

Before sorting the list is: 
88 56 100 2 25 
After sorting the list is: 
2 25 56 88 100