awk sub() not doing replacement - string

Question

The example text file.
in2.txt file:
*{commented out line}* KeyWordName = KeyWordValueAA
KeyWordName = KeyWordValueAA
The regexp finds the string:
awk '/^KeyWordName[[:blank:]]=[[:blank:]].*$/' in2.txt
Output:
KeyWordName = KeyWordValueAA
Command that results in no errors or changed text:
awk '{sub(/^KeyWordName[[:blank:]]=[[:blank:]].*$/, "KeyWordValueBB")}' in2.txt
Removing the double quotes does not work either.
Reading the manpage did not help either.

Answer 1

You need to explicitly print to see any output:
A common awk idiom is to add a 1 after the action:
$ awk '{sub(/^KeyWordName[[:blank:]]=[[:blank:]].*$/, "KeyWordValueBB")}1' file
{commented out line} KeyWordName = KeyWordValueAA
KeyWordValueBB
The 1 is an always-true pattern and since there's no corresponding action, the default action of print is performed (on all input lines).
Or you can just use print:
$ awk '{sub(/^KeyWordName[[:blank:]]=[[:blank:]].*$/, "KeyWordValueBB")} {print}' file
{commented out line} KeyWordName = KeyWordValueAA
KeyWordValueBB
To change the file when you don't have the -i option, save to a temporary file and rename it to your file (that's what -i is doing for you, anyway). By using && we are sure the mv command will only be executed if the awk terminates with success. Stil, you might want to save a copy of your original file first in case the awk is "successful" from the OS point of view, but doesn't do what you expected!
awk '{ ... }' file > tmp && mv tmp file