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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.

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 <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)

GNU                                                                            2021-03-22                                                                  STRVERSCMP(3)

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