strverscmp

strverscmp - compare two version strings

#define _GNU_SOURCE

#include <string.h>
 I int strverscmp(const char * s1 , const char * s2 );

Often one has files R jan1 , jan2 , ..., jan9 , jan10 , ... and it feels wrong when ls(1) orders them R 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 R strverscmp (). Thus, the task of R strverscmp () is to compare two strings and find the "right" order, while strcmp(3) only finds the lexicographic order. This function does not use the locale category R 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 zeroes are interpreted as if they have a decimal point in front (so that in particular digit strings with more leading zeroes come before digit strings with fewer leading zeroes). Thus, the ordering is R 000 , 00 , 01 , 010 , 09 , 0 , 1 , 9 , 10 .

The R 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.

This function is a GNU extension.

rename(1), strcasecmp(3), strcmp(3), strcoll(3), feature_test_macros(7)