1 .\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>
2 .\" and Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com>
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26 .TH STRVERSCMP 3 2017-03-13 "GNU" "Linux Programmer's Manual"
28 strverscmp \- compare two version strings
31 .BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
33 .B #include <string.h>
35 .BI "int strverscmp(const char *" s1 ", const char *" s2 );
39 .IR jan1 ", " jan2 ", ..., " jan9 ", " jan10 ", ..."
40 and it feels wrong when
43 .IR jan1 ", " jan10 ", ..., " jan2 ", ..., " jan9 .
44 .\" classical solution: "rename jan jan0 jan?"
45 In order to rectify this, GNU introduced the
49 which is implemented using
56 is to compare two strings and find the "right" order, while
58 finds only the lexicographic order.
59 This function does not use
62 so is meant mostly for situations
63 where the strings are expected to be in ASCII.
65 What this function does is the following.
66 If both strings are equal, return 0.
67 Otherwise, find the position
68 between two bytes with the property that before it both strings are equal,
69 while directly after it there is a difference.
70 Find the largest consecutive digit strings containing (or starting at,
71 or ending at) this position.
72 If one or both of these is empty,
75 would have returned (numerical ordering of byte values).
76 Otherwise, compare both digit strings numerically, where digit strings with
77 one or more leading zeros are interpreted as if they have a decimal point
78 in front (so that in particular digit strings with more leading zeros
79 come before digit strings with fewer leading zeros).
81 .IR 000 ", " 00 ", " 01 ", " 010 ", " 09 ", " 0 ", " 1 ", " 9 ", " 10 .
85 function returns an integer
86 less than, equal to, or greater than zero if
88 is found, respectively, to be earlier than, equal to,
92 For an explanation of the terms used in this section, see
98 Interface Attribute Value
101 T} Thread safety MT-Safe
103 .\" FIXME: The marking is different from that in the glibc manual,
106 .\" strverscmp: MT-Safe locale
108 .\" glibc manual says strverscmp should have marking locale because it calls
109 .\" isdigit() multiple times and isdigit() uses locale variable.
110 .\" But isdigit() has two implementations. With different compiling conditions,
111 .\" we may call isdigit() in macro, then strverscmp() should not have locale
114 This function is a GNU extension.
116 The program below can be used to demonstrate the behavior of
120 to compare the two strings given as its command-line arguments.
121 An example of its use is the following:
125 $ i\fB./a.out jan1 jan10\fP
138 main(int argc, char *argv[])
143 fprintf(stderr, "Usage: %s <string1> <string2>\\n", argv[0]);
147 res = strverscmp(argv[1], argv[2]);
149 printf("%s %s %s\\n", argv[1],
150 (res < 0) ? "<" : (res == 0) ? "==" : ">", argv[2]);