Question

I am using the below code to change an existing awk script so that I can add more and more cases with a simple command.

echo `awk '{if(/#append1/){print "pref'"$1"'=0\n" $0 "\n"} else{print $0 "\n"}}' tf.a

note that the first print is "pref'"$1"'=0\n" so it is referring to the variable $1 in its environment, not in awk itself.

The command ./tfb.a "c" should change the code from:

BEGIN{
#append1
}
...

to:

BEGIN{
prefc=0
#append1
}
...

However, it gives me everything on one line.

Does anyone know why this is?

Answer 1

If you take awk right out of the equation you can see what’s going on:

# Use a small test file instead of an awk script
$ cat xxx
hello
there
$ echo `cat xxx`
hello there
$ echo "`cat xxx`"
hello
there
$ echo "$(cat xxx)"
hello
there
$

The backtick operator expands the output into shell “words” too soon. You could play around with the $IFS variable in the shell (yikes), or you could just use double-quotes.

If you’re running a modern sh (e.g. ksh or bash, not the “classic” Bourne sh), you may also want to use the $() syntax (it’s easier to find the matching start/end delimiter).