| .\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl> |
| .\" |
| .\" 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| .\" manual page may be incorrect or out-of-date.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. |
| .\" |
| .TH STRVERSCMP 3 2001-12-19 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| strverscmp \- compare two version strings |
| .SH SYNOPSIS |
| .nf |
| .B #define _GNU_SOURCE |
| .br |
| .B #include <string.h> |
| .sp |
| .BI "int strverscmp(const char *" s1 ", const char *" s2 ); |
| .fi |
| .SH DESCRIPTION |
| Often one has files |
| .IR jan1 ", " jan2 ", ..., " jan9 ", " jan10 ", ..." |
| and it feels wrong when |
| .B ls |
| orders them |
| .IR jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 ". |
| .\" classical solution: "rename jan jan0 jan?" |
| In order to rectify this, GNU introduced the |
| .B \-v |
| option to |
| .BR ls (1), |
| which is implemented using |
| .BR versionsort (3), |
| which again uses |
| .BR strverscmp (). |
| |
| Thus, the task of |
| .BR strverscmp () |
| is to compare two strings and find the "right" order, while |
| .BR 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 |
| .BR 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 |
| .IR 000 ", " 00 ", " 01 ", " 010 ", " 09 ", " 0 ", " 1 ", " 9 ", " 10 . |
| .SH "RETURN VALUE" |
| The \fBstrverscmp\fP() function returns an integer |
| less than, equal to, or greater than zero if \fIs1\fP |
| is found, respectively, to be earlier than, equal to, |
| or later than \fIs2\fP. |
| .SH "CONFORMING TO" |
| This function is a GNU extension. |
| .SH "SEE ALSO" |
| .BR rename (1), |
| .BR strcasecmp (3), |
| .BR strcmp (3), |
| .BR strcoll (3) |