strverscmp(3) — Linux manual page


strverscmp(3)           Library Functions Manual           strverscmp(3)

NAME         top

       strverscmp - compare two version strings

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <string.h>

       int strverscmp(const char *s1, const char *s2);

DESCRIPTION         top

       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         top

       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         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ strverscmp()                        │ Thread safety │ MT-Safe │

STANDARDS         top


EXAMPLES         top

       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>

       main(int argc, char *argv[])
           int res;

           if (argc != 3) {
               fprintf(stderr, "Usage: %s <string1> <string2>\n", argv[0]);

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

           printf("%s %s %s\n", argv[1],
                  (res < 0) ? "<" : (res == 0) ? "==" : ">", argv[2]);


SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15                  strverscmp(3)

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