Using shell variables in an awk script

Question

So, I'm trying to find out some ways to pass external shell variables to an awk script, but I'm confused about ' and ".

First, I tried this with a shell script.

$ v=123test
$ echo $v
123test
$ echo "$v"
123test

Then I tried awk.

$ awk 'BEGIN{print "'$v'"}'
$ 123test
$ awk 'BEGIN{print '"$v"'}'
$ 123

Lastly, this is what I tried.

$ awk 'BEGIN{print " '$v' "}'
$  123test
$ awk 'BEGIN{print ' "$v" '}'
awk: cmd. line:1: BEGIN{print
awk: cmd. line:1:             ^ unexpected newline or end of string 

Where is the difference?

Answer 1

Using -v is, imo, The best way because it's most portable.

variable="line one\nline two" awk -v var="$variable" 'BEGIN {print var}' line one line two

This should be compatible with most aw. The variable is available in the BEGIN block as well.

If you're dealing with multiple variables:

awk -v a="$var1" -v b="$var2" 'BEGIN {print a,b}'