Question

I’m using a find command to find all files of a certain format, that command has been golden. I’m piping that output into an awk command and I want to use the last underscore as a field separator. The problem being that depending on the path the file is in, there could be one or two underscores before the fact.

find . -regex ".*prob[0-9]*_.*" | awk 'BEGIN { FS = "_.*$" } { print $1 " " $2 }'

I get what’s wrong with the regular expression in my field separator, it thinks to separate on the underscore and whatever follows, is there away to specify just the single character itself. Moreover, how do I specifically use a field separator on the last occurrence of a character.

This is somewhat an extension of a question I asked earlier:
Suppress output to StdOut when piping echo

The files I get are generally like this, the wrinkle being that the directory can have an underscore as well:
/the/directory/probXXXXX_XX

where X is any integer.

A workaround I’ve been thinking of is separating at every underscore and then print every column… I’d rather like to get it working in the method above though.

Answer 1

A trick of awk that is not obvious is that $ is an operator; you can use it with a variable or even an expression, and in particular with expressions involving the predefined variable NF: $NF gets the last field, $(NF - 1) the second last field.