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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)  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
       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.

CONFORMING TO

       This function is a GNU extension.

SEE ALSO

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

COLOPHON

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