SED/tr etc.. : How to comment out a line that contains “string” in a file?

Question

my file contains lines such as these:

-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 INPUT -m state --state NEW -m tcp -p tcp --dport 2002 -j ACCEPT

i want to comment out ( add # infront of ) the line that is

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

how can i do this via SED or some other method via command line ?

should i seek for .. eg.

2001

and then comment out that whole line ( add # infront of )

or should i search for the entire line and then replace it with a new one that contains # ?

what would be the most practical method ? ( fastest )

Answer 1

Through sed,

sed '/ 2001 /s/^/#/' file

Add inline edit -i option to save the changes made.

sed -i '/ 2001 /s/^/#/' file

Example:

$ sed '/ 2001 /s/^/#/' 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 INPUT -m state --state NEW -m tcp -p tcp --dport 2002 -j ACCEPT

Answer 2

This awk would do too.

awk '/2001/ {$0="#"$0}1' 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 INPUT -m state --state NEW -m tcp -p tcp --dport 2002 -j ACCEPT