Question

Is there a way to set a variable in my current shell from within awk?

I’d like to do some processing on a file and print out some data; since I’ll read the whole file through, I’d like to save the number of lines — in this case, FNR.

Happens though I can’t seem to find a way to set a shell variable with FNR value; if not this, I’d have to read the FNR from my output file, to set, say num_lines, with FNR value.

I’ve tried some combinations using awk 'END{system(...)}', but could not manage it to work. Any way around this?

Answer 1

$ echo "$var"

$ declare $( awk 'BEGIN{print "var=17"}' )
$ echo "$var"
17

Here’s why you should use declare instead of eval:

$ eval $( awk 'BEGIN{print "echo \"removing all of your files, ha ha ha....\""}' )
removing all of your files, ha ha ha....

$ declare $( awk 'BEGIN{print "echo \"removing all of your files\""}' )
bash: declare: `"removing': not a valid identifier
bash: declare: `files"': not a valid identifier

Note in the first case that eval executes whatever string awk prints, which could accidentally be a very bad thing!