Curly braces in awk reg exp

Question

I am trying to match a fixed number of digits using curly braces in awkbut I get no result.

# This outputs nothing
echo "123" | awk '/^[0-9]{3}$/ {print $1;}' 

# This outputs 123
echo "123" | awk '/^[0-9]+$/ {print $1;}' 

Do I need to do something specific to use curly braces?

Answer 1

Mac OS X awk (BSD awk) works with the first command shown:

$ echo "123" | /usr/bin/awk '/^[0-9]{3}$/ {print $1;}' 
123
$

GNU awk does not. Adding backslashes doesn't help GNU awk. Using option --re-interval does, and so does using --posix.

$ echo "123" | /usr/gnu/bin/awk --re-interval '/^[0-9]{3}$/ {print $1;}' 
123
$ echo "123" | /usr/gnu/bin/awk --posix '/^[0-9]{3}$/ {print $1;}' 
123
$

(I'm not sure where mawk 1.3.3 dated 1996 comes from, but it is probably time to get an updated version of awk for your machine.)