qsort - sort table of data

Syntax

#include <stdlib.h> void qsort (void * base, size_t nel, size_t width, int ( *compar) (const void *, const void *));

Description  The qsort() function is an implementation of the quicksort algorithm. It sorts a table of data

	in place. The contents of the table are sorted in ascending order according to the usersupplied comparison function. base points to the element at the base of the table. nel is the number of elements in the table. width specifies the size of each element in bytes. compar is the name of the user-defined comparison function, which is called by qsort() with two arguments that point to the elements being compared. This function must return an integer less than, equal to, or greater than zero to indicate if the first argument is to be considered less than, equal to, or greater than the second. The comparison function may be defined as follows: /* Program fragment 1 compares two char values */ int comp(const void *a, const void *b) { if(*((const char *)a) < *((const char *) b) ) return(-1); else if(*((const char *)a) > *((const char *) b ) ) return(1); return(0); } /* Program fragment 2 compares two integer values */ int compare(const void *a, const void *b) { return ( *((const int *) a) - *((const int *) b) ); }
Notes	The comparison function need not compare every byte, so arbitrary data may be contained in the elements in addition to the values being compared. Extension In contrast to XPG4, the order of array members that are considered equal by the comparison function is not changed. (End)
See also	stdlib.h.