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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 con-
taining (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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latest version of this page, can be found at
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GNU 2001-12-19 STRVERSCMP(3)
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