strverscmp(3) Library Functions Manual strverscmp(3)
NAME
strverscmp - compare two version strings
LIBRARY
Standard C library (libc, -lc)
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 or-
der to rectify this, GNU introduced the -v option to ls(1), which is im-
plemented 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 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(3) would have returned (numeri-
cal ordering of byte values). Otherwise, compare both digit strings nu-
merically, where digit strings with one or more leading zeros are inter-
preted 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 │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
GNU.
EXAMPLES
The program below can be used to demonstrate the behavior of strver-
scmp(). 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>
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)
Linux man-pages 6.9.1 2024-06-15 strverscmp(3)
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