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   qsort.3p    ( 3 )

отсортировать таблицу данных (sort a table of data)

Пролог (Prolog)

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.

Имя (Name)

qsort — sort a table of data

Синопсис (Synopsis)

#include <stdlib.h>

void qsort(void *base, size_t nel, size_t width, int (*compar)(const void *, const void *));


Описание (Description)

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.


Возвращаемое значение (Return value)

The qsort() function shall not return a value.

Ошибки (Error)

No errors are defined.

The following sections are informative.


Примеры (Examples)

None.

Использование в приложениях (Application usage)

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

Обоснование (Rationale)

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


Будущие направления (Future directions)

None.

Смотри также (See also)

alphasort(3p)

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