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up vote 1 down vote favorite

I have 3 files in a directory

MYO144064T
MYO144064TA
MYO144064TX

Where the digits and 11th character will change. In my csh script, I want to extract the letters 'A' and 'X' probably using grep

The variable $study equals MYO144064

What I have managed so far is very cumbersome

ls | grep $study | cut -c 11 | sed 's/\///'

Which gives me

A
X

How can I do this with minimal processes and without the additional blank line?

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3 Answers 3

up vote 2 down vote accepted 
ls | grep -oP "(?<=$study.)[A-Z]$"

will return any uppercase letter that is preceded by the contents of $study plus one arbitrary character (the T in your example) and followed by the end of the line.

The -P option (Perl regular expressions) is needed to be able to use the positive lookbehind expression (?<=...), but might not be available on every system and platform.

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up vote 0 down vote 
ls | grep $study | grep -o "[AX]$"

returns only the result of 'A' or 'X' as the last character

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The 11th character will change, it may be A or X but could easily be M, Y, O or T –  moadeep Mar 27 '14 at 13:32
    
then ".$" will always get you the last character –  rob Mar 27 '14 at 13:48
up vote 0 down vote

A perl solution:

$ perl -nle 'print chop if length == 11' file
A
X

Or if you can use bash:

while read var
do
    [ ${#var} -eq 11 ] && echo ${var:(-1)}
done < file
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