Question

I have a tab delimited file with 5 columns and need to retrieve a count of just the number of unique lines from column 2. I would normally do this with Perl/Python but I am forced to use the shell for this one.

I have successfully in the past used *nix uniq function piped to wc but it looks like I am going to have to use awk in here.

Any advice would be greatly appreciated. (I have asked a similar question previously about column checks using awk but this is a little different and I wanted to separate it so if someone in the future has this question this will be here)

Many many thanks!
Lilly

Answer 1

No need to use awk.

$ cut -f2 file.txt | sort | uniq | wc -l

should do it.

This uses the fact that tab is cut‘s default field separator, so we’ll get just the content from column two this way. Then a pass through sort works as a pre-stage to uniq, which removes the duplicates. Finally we count the lines, which is the sought number.