strverscmp (3)
Leading comments
Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl> and Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com> %%%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 ...
NAME
strverscmp - compare two version stringsSYNOPSIS
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <string.h> int strverscmp(const char *s1, const char *s2);
DESCRIPTION
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.
RETURN VALUE
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.ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| strverscmp() | Thread safety | MT-Safe |