awk - change value

Question

File contains

TIMEOUT=abc
TIMEOUT=5
TIMEOUT=
xTIMEOUT=5

I need to change from

"TIMEOUT=5" 

to

"TIMEOUT=9"

This command works.
But changes 4th line too, which is not desired

awk '$0 ~ "TIMEOUT=[:0-9:]" { $0 = "TIMEOUT=9" } {print}' file

And this command does not change anything

awk '$0 == "TIMEOUT=[:0-9:]" { $0 = "TIMEOUT=9" } {print}' file

What should I do? THANKS!

Answer 1

This should do:

awk '/^TIMEOUT=[:0-9:]/ { $0 = "TIMEOUT=9" } {print}' file

or even easier:

sed 's/^TIMEOUT=[0-9]/TIMEOUT=9/' file