QSORT(3P)

✨ PROLOG ✨

okay bestie, quick heads up before we dive in 💖 this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so like, go check the corresponding Linux manual page for the deets on Linux behavior), or honestly? the interface may not even be implemented on Linux at all. 🙈

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🎀 NAME 🎀

qsort — sort a table of data. yes that's it. that's the whole vibe. sorting. iconic behavior fr fr ✨

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🌸 SYNOPSIS 🌸

#include <stdlib.h>

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

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💅 DESCRIPTION 💅

okay so first thing: everything described on this reference page is aligned with the ISO C standard. If there's any conflict between what's written here and the ISO C standard? That's unintentional, not a plot twist. This volume of POSIX.1‐2017 defers to the ISO C standard. periodt. 👑

The qsort() function shall sort an array of nel objects, and the initial element of that array is pointed to by base. The size of each object, in bytes, is specified by the width argument. And here's a cute little edge case: if the nel argument has the value zero, then the comparison function pointed to by compar shall not be called and no rearrangement shall take place. like, nothing happens. the array gets to stay exactly as it is. main character energy, no notes. 🦋

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. so like, the order can shuffle around, but the actual contents of each element? untouched. 💖

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. no chaotic flip-flopping, bestie, we need consistency. 🫶

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. And if two members compare as equal, their order in the sorted array is unspecified. ngl that last bit is giving "we don't promise anything" 😭

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⭐ RETURN VALUE ⭐

The qsort() function shall not return a value. it's giving silent but powerful. 💅

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💀 ERRORS 💀

No errors are defined.

The following sections are informative.

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🌈 EXAMPLES 🌈

None. (yes really, that's the whole section, we love a minimalist queen ✨)

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🍓 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. like, your struct can have extra lil friends in there that the comparator simply doesn't care about. so valid. 🎀

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🧚 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

like yes, all three, every time, for each argument, separately. no shortcuts. 🔥

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🔮 FUTURE DIRECTIONS 🔮

None.

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👑 SEE ALSO 👑

• alphasort()
• The Base Definitions volume of POSIX.1‐2017, <stdlib.h>

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💜 COPYRIGHT 💜

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 .

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and that's the whole page bestie!! 💖 this lil masterpiece came from IEEE/The Open Group, dated 2017, and it lives in the manual as QSORT(3P). slay, ate, no crumbs. 🎀✨🦋