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.

EXAMPLE

       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

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