QSORT(3) Linux Programmer's Manual QSORT(3)NAMEqsort - sorts an array
SYNOPSIS
#include <stdlib.h>
void qsort(void *base, size_t nmemb, size_t size,
int(*compar)(const void *, const void *));
DESCRIPTION
The qsort() function sorts an array with nmemb elements of size size.
The base argument points to the start of the array.
The contents of the array are sorted in ascending order according to a
comparison function pointed to by compar, which is called with two
arguments that point to the objects being compared.
The comparison function must return an integer less than, equal to, or
greater than zero if the first argument is considered to be respec‐
tively less than, equal to, or greater than the second. If two members
compare as equal, their order in the sorted array is undefined.
RETURN VALUE
The qsort() function returns no value.
CONFORMING TO
SVr4, 4.3BSD, C99.
NOTE
Library routines suitable for use as the compar argument include str‐
cmp() (see below), alphasort(), and versionsort().
EXAMPLE
For one example of use, see the example under bsearch(3).
Another example is the following example program, which sorts the
strings given in its command-line arguments:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
static int
cmpstringp(const void *p1, const void *p2)
{
/* The actual arguments to this function are "pointers to
pointers to char", but strcmp() arguments are "pointers
to char", hence the following cast plus dereference */
return strcmp(* (char * const *) p1, * (char * const *) p2);
}
int
main(int argc, char *argv[])
{
int j;
assert(argc > 1);
qsort(&argv[1], argc - 1, sizeof(char *), cmpstringp);
for (j = 1; j < argc; j++)
puts(argv[j]);
exit(EXIT_SUCCESS);
}
SEE ALSOsort(1), alphasort(3), strcmp(3), versionsort(3)
2003-11-15 QSORT(3)