SYNOPSIS
#include <stdlib.h>
void qsort(
void *base,
size_t nel,
size_t size,
int (*compar)(const void *, const void *)
);
DESCRIPTION
qsort()
is an implementation of the quicksort algorithm.
It sorts a table of data in place.
- base
Pointer to the element at the base of the table.
- nel
Number of elements in the table.
- size
Size of each element in the table.
- compar
Name of the comparison function,
which is called with two arguments that point
to the elements being compared.
The function passed as
compar
must return an integer less than, equal to,
or greater than zero, according to
whether its first argument is to be considered
less than, equal to, or greater than the second.
strcmp()
uses this same return convention (see
string(3C)).
NOTES
The pointer to the base of the table should be
of type pointer-to-element, and cast to type pointer-to-void.
The comparison function need not compare every byte;
thus, arbitrary data can be contained in the elements
in addition to the values being compared.
The order in the output of two items which compare as equal is unpredictable.
WARNINGS
If
size
is zero, a divide-by-zero error might be generated.
STANDARDS CONFORMANCE
qsort(): AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1, ANSI C
Printable version
