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 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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). Interface Attribute Value strverscmp() Thread safety MT-Safe
CONFORMING TO
This function is a GNU extension.
EXAMPLE
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:
$ i./a.out jan1 jan10
jan1 < jan10
Program source
#define _GNU_SOURCE
#include <string.h>
#include <stdio.h>
#include <stdlib.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 == -1) ? "<" : (res == 0) ? "==" : ">", argv[2]);
exit(EXIT_SUCCESS);
}
SEE ALSO
rename(1), strcasecmp(3), strcmp(3), strcoll(3)
COLOPHON
This page is part of release 4.09 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
