Shell Programming and Scripting

Why does this work:

Code:

awk 'NR==3 sub(FS $NF,x)' inputfile

But not this:

Code:

var=3
awk -v i=$var 'NR==i sub(FS $NF,x)' inputfile

How would you do the same thing as the first line of code, but with a variable?

try with

Code:

 
i="$var"

@itkamaraj: That wouldn't make a difference. At least not on my GNU Bash.

@locoroco: The basic structure of an awk statement is pattern { action }.
1. You sub statement is not enclosed in curly braces.
2. What is the output of the awk statement? Its not printing anything. How did the first statement work?
3. sub (/old/, "new", target) --> this is how sub works. It'll replace the first occurrence of "old" with "new" in target. If target not specified, then it'll consider $0, the whole line.

Here's an example:

Code:

$ cat input
hello world
welcome to earth
$
$ x=2
$
$ awk -v var=$x 'NR==var { sub(/welcome/, "hello"); print }' input
hello to earth
$
$