extract trailer count one liner

dirtdog has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks

I'm stuck trying to extract the Trailer count from a file that contains a Header and Trailer within brackets.

I have the following one-liner so far, but it doesn't quite get exactly what i need

perl -ne 'print "$1\n" if /\[(.*?)\]/;' <filename>

Sample input looks like this:

[HDR20140110230120]
--data content--
[TRL345]
[download]

The data content is swift data and is not surrounded by brackets so is not relevant for this example.

My expected result would be 345 in this example. Also, other samples of what the trailer record could be are:

[TRL0] or [TRL25678]

It's a variable length count with no leading zeroes.

Any help would be greatly appreciated

thanks

Comment on extract trailer count one liner Select or Download Code

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Re: extract trailer count one liner by kennethk (Abbot) on Jan 13, 2014 at 17:38 UTC
Since it looks like your hit contains the letters `TRL` followed by one or more digits, you could express this as `perl -ne 'print "$1\n" if /\[TRL(\d+)\]/;' <filename>` [download] This will also strip off the unwanted alpha chars. #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l] [select]
Re: extract trailer count one liner by hdb (Monsignor) on Jan 13, 2014 at 17:38 UTC
If you are only looking for the digits, try `perl -ne 'print "$1\n" if /\[TRL(\d+)\]/;' <filename>` [download]	[reply] [d/l]
Re: extract trailer count one liner by Anonymous Monk on Jan 13, 2014 at 18:15 UTC
And if the file is large, seek() relative to the end of file before you start to read. Say the known max-length of a trailer plus 50 bytes. Then read lines until you find one that matches the trailer regex.	[reply]