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1 | .\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl> |
| 2 | .\" | |
| 3 | .\" Permission is granted to make and distribute verbatim copies of this | |
| 4 | .\" manual provided the copyright notice and this permission notice are | |
| 5 | .\" preserved on all copies. | |
| 6 | .\" | |
| 7 | .\" Permission is granted to copy and distribute modified versions of this | |
| 8 | .\" manual under the conditions for verbatim copying, provided that the | |
| 9 | .\" entire resulting derived work is distributed under the terms of a | |
| 10 | .\" permission notice identical to this one. | |
| 11 | .\" | |
| 12 | .\" Since the Linux kernel and libraries are constantly changing, this | |
| 13 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
| 14 | .\" responsibility for errors or omissions, or for damages resulting from | |
| 15 | .\" the use of the information contained herein. The author(s) may not | |
| 16 | .\" have taken the same level of care in the production of this manual, | |
| 17 | .\" which is licensed free of charge, as they might when working | |
| 18 | .\" professionally. | |
| 19 | .\" | |
| 20 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
| 21 | .\" the source, must acknowledge the copyright and authors of this work. | |
| 22 | .\" | |
| 23 | .TH STRVERSCMP 3 2001-12-19 "GNU" "Linux Programmer's Manual" | |
| 24 | .SH NAME | |
| 25 | strverscmp \- compare two version strings | |
| 26 | .SH SYNOPSIS | |
| 27 | .nf | |
| 28 | .B #define _GNU_SOURCE | |
| 29 | .br | |
| 30 | .B #include <string.h> | |
| 31 | .sp | |
| 32 | .BI "int strverscmp(const char *" s1 ", const char *" s2 ); | |
| 33 | .fi | |
| 34 | .SH DESCRIPTION | |
| 35 | Often one has files | |
| 36 | .IR jan1 ", " jan2 ", ..., " jan9 ", " jan10 ", ..." | |
| 37 | and it feels wrong when | |
| 38 | .B ls | |
| 39 | orders them | |
| 40 | .IR jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 ". | |
| 41 | .\" classical solution: "rename jan jan0 jan?" | |
| 42 | In order to rectify this, GNU introduced the | |
| 43 | .B \-v | |
| 44 | option to | |
| 45 | .BR ls (1), | |
| 46 | which is implemented using | |
| 47 | .BR versionsort (3), | |
| 48 | which again uses | |
| 49 | .BR strverscmp . | |
| 50 | ||
| 51 | Thus, the task of | |
| 52 | .B strverscmp | |
| 53 | is to compare two strings and find the "right" order, while | |
| 54 | .B strcmp | |
| 55 | only finds the lexicographic order. This function does not use | |
| 56 | the locale category LC_COLLATE, so is meant mostly for situations | |
| 57 | where the strings are expected to be in ASCII. | |
| 58 | ||
| 59 | What this function does is the following. | |
| 60 | If both strings are equal, return 0. Otherwise find the position | |
| 61 | between two bytes with the property that before it both strings are equal, | |
| 62 | while directly after it there is a difference. | |
| 63 | Find the largest consecutive digit strings containing (or starting at, | |
| 64 | or ending at) this position. If one or both of these is empty, | |
| 65 | then return what | |
| 66 | .B strcmp | |
| 67 | would have returned (numerical ordering of byte values). | |
| 68 | Otherwise, compare both digit strings numerically, where digit strings with | |
| 69 | one or more leading zeroes are interpreted as if they have a decimal point | |
| 70 | in front (so that in particular digit strings with more leading zeroes | |
| 71 | come before digit strings with fewer leading zeroes). | |
| 72 | Thus, the ordering is | |
| 73 | .IR 000 ", " 00 ", " 01 ", " 010 ", " 09 ", " 0 ", " 1 ", " 9 ", " 10 . | |
| 74 | .SH "RETURN VALUE" | |
| 75 | The \fBstrverscmp()\fP function returns an integer | |
| 76 | less than, equal to, or greater than zero if \fIs1\fP | |
| 77 | is found, respectively, to be earlier than, equal to, | |
| 78 | or later than \fIs2\fP. | |
| 79 | .SH "CONFORMING TO" | |
| 80 | This function is a GNU extension. | |
| 81 | .SH "SEE ALSO" | |
| 82 | .BR rename (1), | |
| 83 | .BR strcasecmp (3), | |
| 84 | .BR strcmp (3), | |
| 85 | .BR strcoll (3) |