mirror of https://github.com/mkerrisk/man-pages
95 lines
3.3 KiB
Plaintext
95 lines
3.3 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "QSORT" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" qsort
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.SH NAME
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qsort \- sort a table of data
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.SH SYNOPSIS
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.LP
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\fB#include <stdlib.h>
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.br
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.sp
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void qsort(void *\fP\fIbase\fP\fB, size_t\fP \fInel\fP\fB, size_t\fP
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\fIwidth\fP\fB,
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.br
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\ \ \ \ \ \ int (*\fP\fIcompar\fP\fB)(const void *, const void *));
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIqsort\fP() function shall sort an array of \fInel\fP objects,
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the initial element of which is pointed to by
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\fIbase\fP. The size of each object, in bytes, is specified by the
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\fIwidth\fP argument. If the \fInel\fP argument has the value
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zero, the comparison function pointed to by \fIcompar\fP shall not
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be called and no rearrangement shall take place.
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.LP
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The application shall ensure that the comparison function pointed
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to by \fIcompar\fP does not alter the contents of the array.
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The implementation may reorder elements of the array between calls
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to the comparison function, but shall not alter the contents of
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any individual element.
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.LP
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When the same objects (consisting of width bytes, irrespective of
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their current positions in the array) are passed more than
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once to the comparison function, the results shall be consistent with
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one another. That is, they shall define a total ordering on
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the array.
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.LP
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The contents of the array shall be sorted in ascending order according
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to a comparison function. The \fIcompar\fP argument is a
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pointer to the comparison function, which is called with two arguments
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that point to the elements being compared. The application
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shall ensure that the function returns an integer less than, equal
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to, or greater than 0, if the first argument is considered
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respectively less than, equal to, or greater than the second. If two
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members compare as equal, their order in the sorted array is
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unspecified.
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.SH RETURN VALUE
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.LP
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The \fIqsort\fP() function shall not return a value.
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.SH ERRORS
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.LP
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No errors are defined.
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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The comparison function need not compare every byte, so arbitrary
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data may be contained in the elements in addition to the
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values being compared.
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.SH RATIONALE
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.LP
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The requirement that each argument (hereafter referred to as \fIp)\fP
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to the comparison function is a pointer to elements of
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the array implies that for every call, for each argument separately,
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all of the following expressions are nonzero:
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.sp
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.RS
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.nf
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\fB((char *)p - (char *)base) % width == 0
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(char *)p >= (char *)base
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(char *)p < (char *)base + nel * width
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\fP
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.fi
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.RE
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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The Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<stdlib.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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