strverscmp

STRVERSCMP(3)               Linux Programmer's Manual              STRVERSCMP(3)



NAME
       strverscmp - compare two version strings

SYNOPSIS
       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #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(1) 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(3) finds only 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(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 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.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                     Attribute     Value   │
       ├──────────────────────────────────────────────┼───────────────┼─────────┤
       │strverscmp()                                  │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO
       This function is a GNU extension.

EXAMPLES
       The program below can be used to demonstrate the behavior of
       strverscmp().  It uses strverscmp() to compare the two strings given as
       its command-line arguments.  An example of its use is the following:

           $ ./a.out jan1 jan10
           jan1 < jan10

   Program source

       #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>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           res = strverscmp(argv[1], argv[2]);

           printf("%s %s %s\n", argv[1],
                   (res < 0) ? "<" : (res == 0) ? "==" : ">", argv[2]);

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       rename(1), strcasecmp(3), strcmp(3), strcoll(3)

COLOPHON
       This page is part of release 5.13 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.



GNU                                2021-03-22                      STRVERSCMP(3)