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

bash awk sed
user3864928 picture user3864928 · Jul 22, 2014 · Viewed 56k times · Source

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

to comment out let's say the line that contains

2001

i can simply run this SED command:

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

but now how do i revert back ?

as in uncomment that same line ?

i tried

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

that does not work.

Answer

JNLK picture JNLK · Dec 8, 2014

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

sed -i '/<pattern>/s/^/#/g' file

And to uncomment it:

sed -i '/<pattern>/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.

Related questions

How to do a recursive find/replace of a string with awk or sed?

How do I find and replace every occurrence of: subdomainA.example.com with subdomainB.example.com in every text file under the /home/www/ directory tree recursively?

Read More
Bash tool to get nth line from a file

Is there a "canonical" way of doing that? I've been using head -n | tail -1 which does the trick, but I've been wondering if there's a Bash tool that specifically extracts a line (or a range of lines) from a …

Read More
How to merge every two lines into one from the command line?

I have a text file with the following format. The first line is the "KEY" and the second line is the "VALUE". KEY 4048:1736 string 3 KEY 0:1772 string 1 KEY 4192:1349 string 1 KEY 7329:2407 string 2 KEY 0:1774 string 1 I need the value in the same line …

Read More