Question

I want to delete a line if it contains a value that is specified.

2 5 8
1 3 7
8 5 9

So if I wanted to delete a line containing 7 as the third field:

{
if($3 == 7){
####delete the line
}
}

Answer 1

It should be enough to say

$ awk '$3 != 7'

Note that this a numerical comparison, and will omit lines in which the third field is, for example, “0.7e1”, but it will work for the sample data you provide.