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Niklas Rosencrantz
Asked: 2014-02-21 09:13:40 +0800 CST

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

  • 772

I often do e.g.

sudo netstat -lpn |grep :8088

view the output

tcp6       0      0 :::8088                 :::*                    LISTEN      11189/java

and then

sudo kill -kill 11189

I'd like to have a more convenient command exactly like killatport 8088 that uses the tcp port number as a variable and that I can make as an alias to a pipeline that does what I want, but how do I get the PID from the output and pipe it to the kill command? I suppose I might be able to use awk to get the PID from the output from netstat, but how do I safeguard and make an exact port match so that the input 80 won't match 8080 and likewise? Should I make it a C program instead? Or is there already a small utility like this?

bash

2 Answers

  1. Best Answer

    fuser can do that:

    sudo fuser -KILL -k -n tcp 8088
    • 10

  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
    • 3