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qsort(3p) — Linux manual page

QSORT(3P)               POSIX Programmer's ManualQSORT(3P)

PROLOG        top

       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.

NAME        top

       qsort — sort a table of data

SYNOPSIS        top

       #include <stdlib.h>       void qsort(void *base, size_tnel, size_twidth,           int (*compar)(const void *, const void *));

DESCRIPTION        top

       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.       Theqsort() function shall sort an array ofnel objects, the       initial element of which is pointed to bybase.  The size of each       object, in bytes, is specified by thewidth argument. If thenel       argument has the value zero, the comparison function pointed to bycompar shall not be called and no rearrangement shall take place.       The application shall ensure that the comparison function pointed       to bycompar 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. Thecompar 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.

RETURN VALUE        top

       Theqsort() function shall not return a value.

ERRORS        top

       No errors are defined.The following sections are informative.

EXAMPLES        top

       None.

APPLICATION USAGE        top

       The comparison function need not compare every byte, so arbitrary       data may be contained in the elements in addition to the values       being compared.

RATIONALE        top

       The requirement that each argument (hereafter referred to asp) 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

FUTURE DIRECTIONS        top

       None.

SEE ALSO        top

alphasort(3p)       The Base Definitions volume of POSIX.1‐2017,stdlib.h(0p)

COPYRIGHT        top

       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 athttp://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, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017QSORT(3P)

Pages that refer to this page:stdlib.h(0p), alphasort(3p), bsearch(3p)

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