Appending an input file with awk after a pattern (looping?)

Question

I am trying to take a text file called 'input', of the form

line1 
line2
line3
PATTERN
x y z
x y z
lineN

and use awk to place a number (1) after each "x y z" line. I need the lines before the PATTERN and after the "x y z' lines (lineN) in the output. The output I needs looks like this:

line1
line2
line3
PATTERN
x y z   1 
x y z   1
lineN

What I have so far is:

awk '/PATTERN/ {getline; print $0 "   1" }' < input > output 

This gives:

x y z   1

Is it possible to set up a loop to get awk to append an arbitrary number of "x y z" lines or stop after the "x y z" type lines finish?

Answer 1

The looping can help:

awk '/PATTERN/{print;getline;while(!/lineN/){$(NF+1)="  1";print;getline}}1'

Or to extend @Janis idea:

awk '/lineN/{f=0}f{$(NF+1)="  1"}/PATTERN/{f=1}1'

Answer 2

You are saying that only the literal "x y z" lines after PATTERN shall be replaced.

awk '
  /PATTERN/ { f=1 }
  f && /x y z/ { print $0, 1 ; next }
  { print }
'

If it's lines with three arbitrary fields then use

awk '
  /PATTERN/ { f=1 }
  f && NF==3 { print $0, 1 ; next }
  { print }
'