Question

Given a sorted file like so:

AAA 1 2 3
AAA 2 3 4
AAA 3 4 2
BBB 1 1 1
BBB 1 2 1

and a desired output of

AAA 1 2 3
BBB 1 1 1

what’s the best way to achieve this with sed?

Basically, if the col starts with the same field as the previous line, how do I delete it? The rest of the data must be kept on the output.

I imagine there must be some way to do this either using the hold buffer, branching, or the test command.

Answer 1

another way with awk:

awk '!($1 in a){print;a[$1]}' file