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| .TH STRVERSCMP 3 2020-06-09 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| strverscmp \- compare two version strings |
| .SH SYNOPSIS |
| .nf |
| .BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */" |
| .B #include <string.h> |
| .PP |
| .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 |
| .BR ls (1) |
| orders them |
| .IR jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 . |
| .\" classical solution: "rename jan jan0 jan?" |
| In order to rectify this, GNU introduced the |
| .I \-v |
| option to |
| .BR ls (1), |
| which is implemented using |
| .BR versionsort (3), |
| which again uses |
| .BR strverscmp (). |
| .PP |
| Thus, the task of |
| .BR strverscmp () |
| is to compare two strings and find the "right" order, while |
| .BR strcmp (3) |
| finds only the lexicographic order. |
| This function does not use |
| the locale category |
| .BR LC_COLLATE , |
| so is meant mostly for situations |
| where the strings are expected to be in ASCII. |
| .PP |
| 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 (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 |
| .IR 000 ", " 00 ", " 01 ", " 010 ", " 09 ", " 0 ", " 1 ", " 9 ", " 10 . |
| .SH RETURN VALUE |
| The |
| .BR strverscmp () |
| function returns an integer |
| less than, equal to, or greater than zero if |
| .I s1 |
| is found, respectively, to be earlier than, equal to, |
| or later than |
| .IR s2 . |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lb lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR strverscmp () |
| T} Thread safety MT-Safe |
| .TE |
| .\" FIXME: The marking is different from that in the glibc manual, |
| .\" which has: |
| .\" |
| .\" strverscmp: MT-Safe locale |
| .\" |
| .\" glibc manual says strverscmp should have marking locale because it calls |
| .\" isdigit() multiple times and isdigit() uses locale variable. |
| .\" But isdigit() has two implementations. With different compiling conditions, |
| .\" we may call isdigit() in macro, then strverscmp() should not have locale |
| .\" problem. |
| .SH CONFORMING TO |
| This function is a GNU extension. |
| .SH EXAMPLES |
| The program below can be used to demonstrate the behavior of |
| .BR strverscmp (). |
| It uses |
| .BR strverscmp () |
| to compare the two strings given as its command-line arguments. |
| An example of its use is the following: |
| .PP |
| .in +4n |
| .EX |
| $ \fB./a.out jan1 jan10\fP |
| jan1 < jan10 |
| .EE |
| .in |
| .SS Program source |
| \& |
| .EX |
| #define _GNU_SOURCE |
| #include <string.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| int res; |
| |
| if (argc != 3) { |
| fprintf(stderr, "Usage: %s <string1> <string2>\en", argv[0]); |
| exit(EXIT_FAILURE); |
| } |
| |
| res = strverscmp(argv[1], argv[2]); |
| |
| printf("%s %s %s\en", argv[1], |
| (res < 0) ? "<" : (res == 0) ? "==" : ">", argv[2]); |
| |
| exit(EXIT_SUCCESS); |
| } |
| .EE |
| .SH SEE ALSO |
| .BR rename (1), |
| .BR strcasecmp (3), |
| .BR strcmp (3), |
| .BR strcoll (3) |