1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)qsort.3 6.7 (Berkeley) 6/29/91 37.\" 38.Dd June 29, 1991 39.Dt QSORT 3 40.Os 41.Sh NAME 42.Nm qsort, heapsort 43.Nd sort functions 44.Sh SYNOPSIS 45.Fd #include <stdlib.h> 46.Ft void 47.Fn qsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)" 48.Ft int 49.Fn heapsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)" 50.Sh DESCRIPTION 51The 52.Fn qsort 53function is a modified partition-exchange sort, or quicksort. 54The 55.Fn heapsort 56function is a modified selection sort. 57.Pp 58The 59.Fn qsort 60and 61.Fn heapsort 62functions sort an array of 63.Fa nmemb 64objects, the initial member of which is pointed to by 65.Fa base . 66The size of each object is specified by 67.Fa size . 68.Pp 69The contents of the array are sorted in ascending order according to 70a comparison function pointed to by 71.Fa compar , 72which is called with two arguments that point to the objects being 73compared. 74.Pp 75The comparison function must return an integer less than, equal to, or 76greater than zero if the first argument is considered to be respectively 77less than, equal to, or greater than the second. 78.Pp 79The functions 80.Fn qsort 81and 82.Fn heapsort 83are 84.Em not 85stable, that is, if two members compare as equal, their order in 86the sorted array is undefined. 87.Pp 88The 89.Fn qsort 90function is an implementation of C.A.R. Hoare's ``quicksort'' algorithm, 91a variant of partition-exchange sorting; in particular, see D.E. Knuth's 92Algorithm Q. 93.Fn Qsort 94takes O N lg N average time. 95This implementation uses median selection to avoid the traditional 96O N**2 worst-case behavior. 97.Pp 98The 99.Fn heapsort 100function is an implementation of J.W.J. William's ``heapsort'' algorithm, 101a variant of selection sorting; in particular, see D.E. Knuth's Algorithm H. 102.Fn Heapsort 103takes O N lg N worst-case time. 104Its 105.Em only 106advantage over 107.Fn qsort 108is that it uses no additional memory. 109.Sh RETURN VALUES 110The 111.Fn qsort 112function 113returns no value. 114.Pp 115Upon successful completion, 116.Fn heapsort 117returns 0. 118Otherwise, it returns \-1 and the global variable 119.Va errno 120is set to indicate the error. 121.Sh ERRORS 122The 123.Fn heapsort 124function succeeds unless: 125.Bl -tag -width Er 126.It Bq Er EINVAL 127The 128.Fa size 129argument is zero. 130.Sh COMPATIBILITY 131Previous versions of 132.Fn qsort 133did not permit the comparison routine to itself call 134.Fn qsort 3 . 135This is no longer true. 136.Sh SEE ALSO 137.Xr sort 1 , 138.Xr radixsort 3 139.Rs 140.%A Hoare, C.A.R. 141.%D 1962 142.%T "Quicksort" 143.%J "The Computer Journal" 144.%V 5:1 145.%P pp. 10-15 146.Re 147.Rs 148.%A Williams, J.W.J 149.%D 1964 150.%T "Heapsort" 151.%J "Communications of the ACM" 152.%V 7:1 153.%P pp. 347-348 154.Re 155.Rs 156.%A Knuth, D.E. 157.%D 1968 158.%B "The Art of Computer Programming" 159.%V Vol. 3 160.%T "Sorting and Searching" 161.%P pp. 114-123, 145-149 162.Re 163.Sh STANDARDS 164The 165.Fn qsort 166function 167conforms to 168.St -ansiC . 169