mirror of https://github.com/mkerrisk/man-pages
164 lines
4.6 KiB
Groff
164 lines
4.6 KiB
Groff
.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>
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.\" and Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH STRVERSCMP 3 2021-03-22 "GNU" "Linux Programmer's Manual"
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.SH NAME
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strverscmp \- compare two version strings
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.SH SYNOPSIS
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.nf
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.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
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.B #include <string.h>
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.PP
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.BI "int strverscmp(const char *" s1 ", const char *" s2 );
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.fi
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.SH DESCRIPTION
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Often one has files
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.IR jan1 ", " jan2 ", ..., " jan9 ", " jan10 ", ..."
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and it feels wrong when
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.BR ls (1)
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orders them
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.IR jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 .
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.\" classical solution: "rename jan jan0 jan?"
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In order to rectify this, GNU introduced the
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.I \-v
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option to
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.BR ls (1),
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which is implemented using
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.BR versionsort (3),
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which again uses
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.BR strverscmp ().
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.PP
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Thus, the task of
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.BR strverscmp ()
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is to compare two strings and find the "right" order, while
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.BR strcmp (3)
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finds only the lexicographic order.
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This function does not use
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the locale category
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.BR LC_COLLATE ,
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so is meant mostly for situations
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where the strings are expected to be in ASCII.
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.PP
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What this function does is the following.
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If both strings are equal, return 0.
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Otherwise, find the position
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between two bytes with the property that before it both strings are equal,
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while directly after it there is a difference.
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Find the largest consecutive digit strings containing (or starting at,
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or ending at) this position.
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If one or both of these is empty,
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then return what
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.BR strcmp (3)
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would have returned (numerical ordering of byte values).
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Otherwise, compare both digit strings numerically, where digit strings with
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one or more leading zeros are interpreted as if they have a decimal point
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in front (so that in particular digit strings with more leading zeros
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come before digit strings with fewer leading zeros).
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Thus, the ordering is
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.IR 000 ", " 00 ", " 01 ", " 010 ", " 09 ", " 0 ", " 1 ", " 9 ", " 10 .
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.SH RETURN VALUE
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The
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.BR strverscmp ()
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function returns an integer
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less than, equal to, or greater than zero if
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.I s1
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is found, respectively, to be earlier than, equal to,
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or later than
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.IR s2 .
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.ad l
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.nh
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.TS
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allbox;
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lbx lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR strverscmp ()
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T} Thread safety MT-Safe
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.TE
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.hy
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.ad
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.sp 1
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.\" FIXME: The marking is different from that in the glibc manual,
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.\" which has:
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.\"
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.\" strverscmp: MT-Safe locale
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.\"
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.\" glibc manual says strverscmp should have marking locale because it calls
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.\" isdigit() multiple times and isdigit() uses locale variable.
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.\" But isdigit() has two implementations. With different compiling conditions,
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.\" we may call isdigit() in macro, then strverscmp() should not have locale
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.\" problem.
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.SH CONFORMING TO
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This function is a GNU extension.
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.SH EXAMPLES
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The program below can be used to demonstrate the behavior of
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.BR strverscmp ().
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It uses
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.BR strverscmp ()
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to compare the two strings given as its command-line arguments.
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An example of its use is the following:
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.PP
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.in +4n
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.EX
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$ \fB./a.out jan1 jan10\fP
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jan1 < jan10
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.EE
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.in
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.SS Program source
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\&
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.EX
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#define _GNU_SOURCE
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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int
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main(int argc, char *argv[])
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{
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int res;
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if (argc != 3) {
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fprintf(stderr, "Usage: %s <string1> <string2>\en", argv[0]);
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exit(EXIT_FAILURE);
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}
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res = strverscmp(argv[1], argv[2]);
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printf("%s %s %s\en", argv[1],
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(res < 0) ? "<" : (res == 0) ? "==" : ">", argv[2]);
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exit(EXIT_SUCCESS);
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}
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.EE
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.SH SEE ALSO
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.BR rename (1),
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.BR strcasecmp (3),
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.BR strcmp (3),
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.BR strcoll (3)
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