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.

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:

       $ i./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 == -1) ? "<" : (res == 0) ? "==" : ">", argv[2]);

       exit(EXIT_SUCCESS);
   }

SEE ALSO

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

COLOPHON

   This  page  is  part of release 4.09 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/.

---

Free and Open Source Software