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32 .\" @(#)qsort.3 8.1 (Berkeley) 6/4/93
55 .Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *\*[rp]"
62 .Fa "int \*[lp]^compar\*[rp]\*[lp]const void *, const void *\*[rp]"
69 .Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *, void *\*[rp]"
77 .Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *\*[rp]"
84 .Fa "int \*[lp]^compar\*[rp]\*[lp]const void *, const void *\*[rp]"
91 .Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *\*[rp]"
98 .Fa "int \*[lp]^compar\*[rp]\*[lp]const void *, const void *\*[rp]"
100 .Fd #define __STDC_WANT_LIB_EXT1__ 1
106 .Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *, void *\*[rp]"
112 function is a modified partition-exchange sort, or quicksort.
115 function is a modified selection sort.
118 function is a modified merge sort with exponential search
119 intended for sorting data with pre-existing order.
125 functions sort an array of
127 objects, the initial member of which is pointed to by
129 The size of each object is specified by
134 behaves similarly, but
139 .Dq "sizeof(void *) / 2" .
141 The contents of the array
143 are sorted in ascending order according to
144 a comparison function pointed to by
146 which requires two arguments pointing to the objects being
149 The comparison function must return an integer less than, equal to, or
150 greater than zero if the first argument is considered to be respectively
151 less than, equal to, or greater than the second.
155 function behaves identically to
157 except that it takes an additional argument,
159 which is passed unchanged as the last argument to function pointed to
161 This allows the comparison function to access additional
162 data without using global variables, and thus
164 is suitable for use in functions which must be reentrant.
167 function behaves identically to
169 except that it takes a block, rather than a function pointer.
171 The algorithms implemented by
178 stable, that is, if two members compare as equal, their order in
179 the sorted array is undefined.
182 function behaves identically to
184 except that it takes a block, rather than a function pointer.
190 function behaves identically to
192 except that it takes a block, rather than a function pointer.
198 functions are an implementation of C.A.R.
202 a variant of partition-exchange sorting; in particular, see
206 takes O N lg N average time.
207 This implementation uses median selection to avoid its
208 O N**2 worst-case behavior.
212 function is an implementation of
213 .An "J.W.J. William" Ns 's
216 a variant of selection sorting; in particular, see
217 .An "D.E. Knuth" Ns 's
220 takes O N lg N worst-case time.
225 is that it uses almost no additional memory; while
227 does not allocate memory, it is implemented using recursion.
231 requires additional memory of size
234 bytes; it should be used only when space is not at a premium.
238 is optimized for data with pre-existing order; its worst case
239 time is O N lg N; its best case is O N.
247 Memory availability and pre-existing order in the data can make this
252 function behaves the same as
253 .Fn qsort_r , except that:
256 The order of arguments is different
258 The order of arguments to
276 is zero, then the runtime-constraint handler is called, and
279 Note that the handler is called before
281 returns the error, and the handler function might not return.
292 function returns zero on success, non-zero on error.
294 .Rv -std heapsort mergesort
296 A sample program that sorts an array of
298 values in place using
300 and then prints the sorted array to standard output is:
306 * Custom comparison function that compares 'int' values through pointers
307 * passed by qsort(3).
310 int_compare(const void *p1, const void *p2)
312 int left = *(const int *)p1;
313 int right = *(const int *)p2;
315 return ((left > right) - (left < right));
319 * Sort an array of 'int' values and print it to standard output.
324 int int_array[] = { 4, 5, 9, 3, 0, 1, 7, 2, 8, 6 };
325 size_t array_size = sizeof(int_array) / sizeof(int_array[0]);
328 qsort(&int_array, array_size, sizeof(int_array[0]), int_compare);
329 for (k = 0; k < array_size; k++)
330 printf(" %d", int_array[k]);
332 return (EXIT_SUCCESS);
336 The order of arguments for the comparison function used with
338 is different from the one used by
340 and the GNU libc implementation of
342 When porting software written for GNU libc, it is usually possible
347 to work around this problem.
354 and may not be portable to other standards-conforming platforms.
358 did not permit the comparison routine itself to call
360 This is no longer true.
366 functions succeed unless:
371 argument is zero, or,
377 .Dq "sizeof(void *) / 2" .
384 were unable to allocate memory.
393 .%J "The Computer Journal"
401 .%J "Communications of the ACM"
408 .%B "The Art of Computer Programming"
410 .%T "Sorting and Searching"
411 .%P pp. 114-123, 145-149
415 .%T "Optimistic Sorting and Information Theoretic Complexity"
416 .%J "Fourth Annual ACM-SIAM Symposium on Discrete Algorithms"
422 .%T "Engineering a Sort Function"
423 .%J "Software--Practice and Experience"
439 The variants of these functions that take blocks as arguments first appeared in
441 This implementation was created by David Chisnall.
447 was updated to match POSIX.