How to extract string from filename
Janina Sajka
janina at rednote.net
Wed Jul 29 14:59:38 UTC 2015
Not too hard ...
Two steps
1.) Remove the _default.mp3 on the right ...
basename [put filename here] _default.mp3
Example:
basename
Discovery_-_A_Scientific_View_of_Agriculture_p0053gbd_default.mp3
_default.mp3
Take the result into the following command:
${foo##*_}
Example:
${Discovery_-_A_Scientific_View_of_Agriculture_p0053gbd##*_}
You can probably combine these into a one liner. And, if you've got a
lot of files in a directory, you just loop through:
for i in $(ls); do
[[above two command here----
done
PS: I didn't know the second step when I read your post. I googled for:
bash string word right
And found the very slick second step on stackexchange.
Janina
Tony Baechler writes:
> Hi all,
>
> The recent discussion on shell scripts got me thinking. A couple of posters
> invited people to post problems they're having with scripts to the list, so
> here goes.
>
> I have not actually written a script for this because I'm not sure how to go
> about it. I would normally use cut, but I need to cut from right to left.
> The cut help doesn't indicate a way to do this. You can only cut from the
> beginning of the line or a range of bytes. The problem is each line
> (filenames, to be exact) are of different lengths, so it's impossible to
> know what range of bytes I need.
>
> What I'm trying to do is extract the BBC PID from the downloaded files. It's
> a lower case alphanumeric string which starts with a letter and is eight
> characters. In my case, the first letter is always "b" or "p," so if I
> could use something like grep to just extract the first lower case letter
> followed by a number up to the next underscore, that would be good. I don't
> think grep will just print a matching phrase, only the matching line. Here
> are some example filenames:
>
> 5_live_Science_-_Coding_and_Computers_b062dj5j_default.mp3
> Witness_-_The_Sinking_of_the_USS_Indianapolis_p02wdykn_default.mp3
> Discovery_-_A_Scientific_View_of_Agriculture_p0053gbd_default.mp3
> Click_-_05_10_2010_p00b18gp_default.mp3
>
> As you can see, they all follow a similar format. If I could go from right
> to left, I would simply cut "_default.mp3" and extract the preceeding 8
> bytes, but I can't figure out how. What I'm trying to do is first extract
> the PIDs, hopefully preserving the filenames in the process. Once they are
> extracted (or printed to stdout), I want to use wget to download the BBC
> programme page. If you go to www.bbc.co.uk/programme/bXXXXXXX, you'll get a
> web page displaying the broadcast date, description and notes. I would like
> to download those pages.
>
> Any help with this would be greatly appreciated. Thanks in advance.
>
> --------------------
> Tony Baechler, Baechler Access Technology Services
> Putting accessibility at the forefront of technology
> mailto:bats at batsupport.com
> Phone: 1-619-746-8310 Fax: 1-619-449-9898
>
> _______________________________________________
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--
Janina Sajka, Phone: +1.443.300.2200
sip:janina at asterisk.rednote.net
Email: janina at rednote.net
Linux Foundation Fellow
Executive Chair, Accessibility Workgroup: http://a11y.org
The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
Chair, Protocols & Formats http://www.w3.org/wai/pf
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