strverscmp — compare two version strings
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <string.h>
int
strverscmp( |
const char *s1, |
const char *s2); |
Often one has files jan1,
jan2, ..., jan9, jan10,
... and it feels wrong when ls(1) orders them
jan1, jan10, ..., jan2, ..., jan9. In order to rectify this, GNU
introduced the −v option to
ls(1), which is implemented
using versionsort(3), which again
uses strverscmp().
Thus, the task of strverscmp() is to compare two strings and
find the "right" order, while strcmp(3) finds only the
lexicographic order. This function does not use the locale
category LC_COLLATE, so is
meant mostly for situations where the strings are expected to
be in ASCII.
What this function does is the following. If both strings
are equal, return 0. Otherwise, find the position between two
bytes with the property that before it both strings are
equal, while directly after it there is a difference. Find
the largest consecutive digit strings containing (or starting
at, or ending at) this position. If one or both of these is
empty, then return what strcmp(3) would have
returned (numerical ordering of byte values). Otherwise,
compare both digit strings numerically, where digit strings
with one or more leading zeros are interpreted as if they
have a decimal point in front (so that in particular digit
strings with more leading zeros come before digit strings
with fewer leading zeros). Thus, the ordering is 000, 00,
01, 010, 09,
0, 1, 9,
10.
The strverscmp() function
returns an integer less than, equal to, or greater than zero
if s1 is found,
respectively, to be earlier than, equal to, or later than
s2.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
strverscmp() .\" FIXME: the
following marking is different from which in glibc
manual. .\" strverscmp: MT-Safe locale .\" glibc
manual says strverscmp should have marking locale
because it calls .\" isdigit() multiple times and
isdigit() uses locale variable. .\" But isdigit() has
two implementations. With different compiling
conditions, .\" we may call isdigit() in macro, then
strverscmp() should not have locale .\" problem. |
Thread safety | MT-Safe |
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (C) 2001 Andries Brouwer <aebcwi.nl> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END |