# qsort(3f) [bsd man page]

```QSORT(3F)																 QSORT(3F)

NAME
qsort - quick sort

SYNOPSIS
subroutine qsort (array, len, isize, compar)
external compar
integer*2 compar

DESCRIPTION
One  dimensional  array	contains the elements to be sorted.  len is the number of elements in the array.  isize is the size of an element,
typically -

4 for integer and real
8 for double precision or complex
16 for double complex
(length of character object) for character arrays

Compar is the name of a user supplied integer*2 function that will determine the sorting order.	This function will be called with 2  argu-
ments that will be elements of array.  The function must return -

negative if arg 1 is considered to precede arg 2
zero if arg 1 is equivalent to arg 2
positive if arg 1 is considered to follow arg 2

On return, the elements of array will be sorted.

FILES
/usr/lib/libU77.a

qsort(3)

4.2 Berkeley Distribution					   May 15, 1985 							 QSORT(3F)```

## Check Out this Related Man Page

```QSORT(3)						     Linux Programmer's Manual							  QSORT(3)

NAME
qsort, qsort_r - sort an array

SYNOPSIS
#include <stdlib.h>

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

void qsort_r(void *base, size_t nmemb, size_t size,
int (*compar)(const void *, const void *, void *),
void *arg);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

qsort_r(): _GNU_SOURCE

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.

The  qsort_r()  function is identical to qsort() except that the comparison function compar takes a third argument.  A pointer is passed to
the comparison function via arg.  In this way, the comparison function does not need to use global  variables  to  pass	through  arbitrary
arguments, and is therefore reentrant and safe to use in threads.

RETURN VALUE
The qsort() and qsort_r() functions return no value.

VERSIONS
qsort_r() was added to glibc in version 2.8.

ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).

+-------------------+---------------+---------+
|Interface	   | Attribute	   | Value   |
+-------------------+---------------+---------+
|qsort(), qsort_r() | Thread safety | MT-Safe |
+-------------------+---------------+---------+

CONFORMING TO
qsort(): POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

NOTES
To compare C strings, the comparison function can call strcmp(3), as shown in the example below.

EXAMPLE
For one example of use, see the example under bsearch(3).

Another example is the following program, which sorts the strings given in its command-line arguments:

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

static int
cmpstringp(const void *p1, const void *p2)
{
/* The actual arguments to this function are "pointers to
pointers to char", but strcmp(3) 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;

if (argc < 2) {
fprintf(stderr, "Usage: %s <string>...
", argv);
exit(EXIT_FAILURE);
}

qsort(&argv, argc - 1, sizeof(char *), cmpstringp);

for (j = 1; j < argc; j++)
puts(argv[j]);
exit(EXIT_SUCCESS);
}