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.

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

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

	   printf("%s %s %s
", 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 4.15 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
								    2017-09-15							     STRVERSCMP(3)