qsort()

Sorts an array.

  #include <stdlib.h>
  
  void qsort(void *base,size_t nmemb, size_t size,
  
  int (*compare) (const void *, const void *))    

base

A pointer to the array to be sorted.

nmemb

The number of elements.

size

The size of a single element, expressed as a number of characters.

compare

A pointer to a comparison function.

The qsort() function sorts an array using the Quicksort algorithm. It sorts the array without displacing it; the array occupies the same memory it had before the call to qsort().

• The base argument is a pointer to the base of the array to be sorted.
• The nmemb argument specifies the number of array elements to sort.
• The size argument specifies the size of an array element.

The compare argument is a pointer to a programmer-supplied compare function. The function takes two pointers to different array elements and compares them based on the key. If the two elements are equal, compare must return a zero.

The compare function must return a negative number if the first element is less than the second. Likewise, the function must return a positive number if the first argument is greater than the second.