NAME

       strverscmp - compare two version strings

LIBRARY

       Standard C library (libc, -lc)

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 │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       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 <stdio.h>
       #include <stdlib.h>
       #include <string.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)