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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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QSORT(3P) POSIX Programmer's Manual QSORT(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
qsort — sort a table of data
#include <stdlib.h>
void qsort(void *base, size_t nel, size_t width,
int (*compar)(const void *, const void *));
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
The qsort() function shall sort an array of nel objects, the
initial element of which is pointed to by base. The size of each
object, in bytes, is specified by the width argument. If the nel
argument has the value zero, the comparison function pointed to
by compar shall not be called and no rearrangement shall take
place.
The application shall ensure that the comparison function pointed
to by compar does not alter the contents of the array. The
implementation may reorder elements of the array between calls to
the comparison function, but shall not alter the contents of any
individual element.
When the same objects (consisting of width bytes, irrespective of
their current positions in the array) are passed more than once
to the comparison function, the results shall be consistent with
one another. That is, they shall define a total ordering on the
array.
The contents of the array shall be sorted in ascending order
according to a comparison function. The compar argument is a
pointer to the comparison function, which is called with two
arguments that point to the elements being compared. The
application shall ensure that the function returns an integer
less than, equal to, or greater than 0, if the first argument is
considered respectively less than, equal to, or greater than the
second. If two members compare as equal, their order in the
sorted array is unspecified.
The qsort() function shall not return a value.
No errors are defined.
The following sections are informative.
None.
The comparison function need not compare every byte, so arbitrary
data may be contained in the elements in addition to the values
being compared.
The requirement that each argument (hereafter referred to as p)
to the comparison function is a pointer to elements of the array
implies that for every call, for each argument separately, all of
the following expressions are non-zero:
((char *)p - (char *)base) % width == 0
(char *)p >= (char *)base
(char *)p < (char *)base + nel * width
None.
alphasort(3p)
The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any
discrepancy between this version and the original IEEE and The
Open Group Standard, the original IEEE and The Open Group
Standard is the referee document. The original Standard can be
obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 QSORT(3P)
Pages that refer to this page: stdlib.h(0p), alphasort(3p), bsearch(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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