Oneliner command to use kill given tcp port number instead of PID?

Solution 1:

fuser can do that:

sudo fuser -KILL -k -n tcp 8088

Solution 2:

A command can be formulated like this:

netstat -lpn | grep ":1234\b" | awk '{sub(/\/.*/, "", $NF); print $NF}' | xargs -i kill -kill {}

Explanation:

1. netstat -ltpn

   • This lists the listening ports (l) on TCP (t) and their programs (p) without resolving port numbers to names (n).

2. grep ":1234\b"

   • This searches for :1234 followed by a boundary (\b), indicating the end of the word (or number, in our case). This makes sure that we don't catch :12345 for example.

3. awk '{sub(/\/.*/, "", $NF); print $NF}'

   • This

     • substitutes sub(/regex/,"replacewith", #fieldnumber)
     • this regex \/.*
     • with nothing ""
     • in the field $NF, which means the last field (i.e. the field that contains PID/program)
     • then prints it print $NF.

     The regex \/.* matches a literal / and everything after it, and then we're replacing it with nothing, essentially deleting it, so we're left with only the PID number in that field.

4. xargs -i kill -kill {}

   • xargs -i is a program that allows you to make the output of the previous command act as the input to another command. Our command is kill -kill {} where {} indicates "the output from the previous command in the pipeline", which is our PID number.

Note: this whole command might be a little bit dangerous because you might accidentally kill something you didn't want to. It could use with a little bit more sanitization. Just make sure you get the correct port number when using it.

If you want to make this into a function, you can add the following to your ~/.bashrc:

killatport(){
    netstat -lpn | grep ":$1\b" | awk '{sub(/\/.*/, "", $NF); print $NF}' | xargs -i kill -kill {}
}

Save and apply the changes using source ~/.bashrc. Now, you can use the function like this:

killatport 8088