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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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bdiff(1)						      General Commands Manual							  bdiff(1)

NAME
bdiff - Finds differences in large files SYNOPSIS
bdiff file1 file2 [number] [-s] bdiff - file2 [number] [-s] bdiff file1 - [number] [-s] The bdiff command compares file1 and file2 and writes information about their differing lines to standard output. If either filename is - (dash), bdiff reads standard input. OPTIONS
Suppresses error messages. (May either precede or follow the number argument if it is specified.) DESCRIPTION
The bdiff command uses diff to find lines that must be changed in two files to make them identical (see the diff command). Its primary purpose is to permit processing of files that are too large for diff. The bdiff command ignores lines common to the beginning of both files, splits the remainders into sections of number lines, and runs diff on the sections. The output is then processed to make it look as if diff had processed the files whole. If you do not specify number, a system default is used. In some cases, the number you specify or the default number may be too large for diff. If bdiff fails, specify a smaller value for number and try again. Note that because of file segmenting, bdiff does not necessarily find the smallest possible set of file differences. In general, although the output is similar, using bdiff is not the equivalent of using diff. NOTES
The diff command is executed by a child process, generated by forking, and communicates with bdiff through pipes. It should not normally be necessary to use this command, since diff can handle most large files. EXIT STATUS
No differences. Differences found. An error occurred. SEE ALSO
Commands: diff(1), diff3(1) bdiff(1)
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