strverscmp

STRVERSCMP(3)              Linux Programmer's Manual             STRVERSCMP(3)



NAME
       strverscmp - compare two version strings

SYNOPSIS
       #define _GNU_SOURCE
       #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 orders them jan1, jan10, ..., jan2, ..., jan9.  In  order
       to rectify this, GNU introduced the -v option to ls(1), which is imple-
       mented using versionsort(3), which again uses strverscmp.

       Thus, the task of strverscmp is to compare two  strings  and  find  the
       "right"  order,  while  strcmp only finds 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  prop-
       erty  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 would have returned  (numerical
       ordering of byte values).  Otherwise, compare both digit strings numer-
       ically, where digit strings with one or more leading zeroes are  inter-
       preted  as if they have a decimal point in front (so that in particular
       digit strings with more leading zeroes come before digit  strings  with
       fewer  leading zeroes).  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.

CONFORMING TO
       This function is a GNU extension.

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



GNU                               2001-12-19                     STRVERSCMP(3)