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 or-
       der  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 con-
       taining  (or  starting at, or ending at) this position.  If one or both
       of these is empty, then return what strcmp(3) would have returned  (nu-
       merical  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  at-
       tributes(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 strver-
       scmp().  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 5.05 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                               2019-03-06                     STRVERSCMP(3)