How to UNCOMMENT a line that contains a specific string using Sed?

Question

The lines in the file :

-A INPUT -m state --state NEW -m tcp -p tcp --dport 2000 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 2001 -j ACCEPT
-A          


        

Answer 1

Yes, to comment line containing specific string with sed, simply do:

sed -i '//s/^/#/g' file

And to uncomment it:

sed -i '//s/^#//g' file

In your case:

sed -i '/2001/s/^/#/g' file    (to comment out)
sed -i '/2001/s/^#//g' file    (to uncomment)

Option "g" at the end means global change. If you want to change only a single instance of pattern, just skip this.