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Top Forums Shell Programming and Scripting Finding longest common substring among filenames Post 302267476 by cmcnorgan on Friday 12th of December 2008 12:29:27 PM
Old 12-12-2008
Finding longest common substring among filenames

I will be performing a task on several directories, each containing a large number of files (2500+) that follow a regular naming convention:

YYYY_MM_DD_XX.foo_bar.A.B.some_different_stuff.EXT

What I would like to do is automatically discover the part of the filenames that are common to all 2500 files, so that a script could use that as a base name. In practice, this will end up being "YYYY_MM_DD_XX.foo_bar."

I figured out as far as I'll have to use ls to get all the filenames, but there's no command that I know of that will find the largest substring that exists among a large number of strings. I thought perhaps there would be some sed guru out there that would find this problem trivial. You sed experts always blow my mind.
 

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PCRE_GET_SUBSTRING(3)					     Library Functions Manual					     PCRE_GET_SUBSTRING(3)

NAME
PCRE - Perl-compatible regular expressions SYNOPSIS
#include <pcre.h> int pcre_get_substring(const char *subject, int *ovector, int stringcount, int stringnumber, const char **stringptr); int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector, int stringcount, int stringnumber, PCRE_SPTR16 *stringptr); int pcre32_get_substring(PCRE_SPTR32 subject, int *ovector, int stringcount, int stringnumber, PCRE_SPTR32 *stringptr); DESCRIPTION
This is a convenience function for extracting a captured substring. The arguments are: subject Subject that has been successfully matched ovector Offset vector that pcre[16|32]_exec() used stringcount Value returned by pcre[16|32]_exec() stringnumber Number of the required substring stringptr Where to put the string pointer The memory in which the substring is placed is obtained by calling pcre[16|32]_malloc(). The convenience function pcre[16|32]_free_sub- string() can be used to free it when it is no longer needed. The yield of the function is the length of the substring, PCRE_ERROR_NOMEMORY if sufficient memory could not be obtained, or PCRE_ERROR_NOSUBSTRING if the string number is invalid. There is a complete description of the PCRE native API in the pcreapi page and a description of the POSIX API in the pcreposix page. PCRE 8.30 24 June 2012 PCRE_GET_SUBSTRING(3)
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