STRVERSCMP

NAME

strverscmp - compare two version strings

SYNOPSIS

#define _GNU_SOURCE


#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 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 only finds 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 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 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.

CONFORMING TO

This function is a GNU extension.