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Rockbox mail archiveSubject: Re: how is strnatcmp aka "Interpret numbers while sorting" supposed to sort?Re: how is strnatcmp aka "Interpret numbers while sorting" supposed to sort?
From: codemonkey <codemonkey_at_interthingy.net>
Date: Thu, 19 Mar 2009 11:03:29 -0700 Are you guys aware that there's a quasi-standard regarding this in the GNU libraries? See the following excerpt from Fedora "info ls" and "man strverscmp". ~ray PS: I've found that "ls -v" works well for sorting MP3s with track numbering, etc. I don't know if it handles all of the cases described in this thread though. Maybe GNU's implementation is worth borrowing for rockbox? ------ $ info ls (...excerpt...) 10.1.4 More details about version sort -------------------------------------- The version sort takes into account the fact that file names frequently include indices or version numbers. Standard sorting functions usually do not produce the ordering that people expect because comparisons are made on a character-by-character basis. The version sort addresses this problem, and is especially useful when browsing directories that contain many files with indices/version numbers in their names: $ ls -1 $ ls -1v foo.zml-1.gz foo.zml-1.gz foo.zml-100.gz foo.zml-2.gz foo.zml-12.gz foo.zml-6.gz foo.zml-13.gz foo.zml-12.gz foo.zml-2.gz foo.zml-13.gz foo.zml-25.gz foo.zml-25.gz foo.zml-6.gz foo.zml-100.gz Note also that numeric parts with leading zeros are considered as fractional one: $ ls -1 $ ls -1v abc-1.007.tgz abc-1.007.tgz abc-1.012b.tgz abc-1.01a.tgz abc-1.01a.tgz abc-1.012b.tgz This functionality is implemented using the `strverscmp' function. ------ $ man strverscmp STRVERSCMP(3) Linux Programmer’s Manual STRVERSCMP(3) NAME strverscmp - compare two version strings SYNOPSIS #define _GNU_SOURCE #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 zeroes are interpreted as if they have a decimal point in front (so that in particular digit strings with more leading zeroes come before digit strings with fewer leading zeroes). 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), feature_test_macros(7) GNU 2001-12-19 STRVERSCMP(3) Received on 2009-03-19 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |