Using multiple awk statements in a linux command

Question

I am executing a bash script in php file.

1. I have a text file.
2. I have to extract last 100 lines of the file.
3. In these 100 lines I have to extract lines with character "A" in third column.
4. Among these shortlisted lines I have to get the line number of the line whose second column has number "2".

This is my code, which is not providing any output.

<?php

$eff="195";
$chain="B";
$struct_pos="2";

$pre_line=exec("tail $i.dssp -n $eff | awk '$3==$chain'| awk -F' ' -v var=$struct_pos '{if ($2==var) print FNR}'");

?>

However, following codes works properly, in which I have removed one of the awk statements.

$pre_line=exec("tail $i.dssp -n $eff | awk -F' ' -v var=$struct_pos '{if ($2==var) print FNR}'");

$pre_line=exec("tail $i.dssp -n $eff | awk '$3==$chain'");   

What is the solution to this problem ?

Answer 1

尝试这个..，

$pre_line=exec("tail $i.dssp -n $eff | awk '$3==\"'$chain'\"'| awk -F' ' '{if ($2=='$struct_pos') print FNR}'");