signal0?

Or ‘Where did the name signal0 come from?’

It comes from a ‘trick’ I like to use in unix shell scripts.

Basically when you want to check to see if a process is running with a given process ID in unix there are a lot of ways to check - but the way I think is the best is to execute a ‘kill -0 <pid>’. On my laptop I want to check if there is a process with a PID of 777:

$ kill -0 777
-bash: kill: (777) - No such process
$ echo $?
1

Or, used in a simple shell script that tells your nginx process is running:

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#!/bin/sh

_pid=`cat /var/run/nginx.pid`
if kill -0 $_pid 2> /dev/null
then
    echo "nginx pid $_pid is running."
else
    echo "nginx pid $_pid is not running."
fi

A while back (like 2010?) I was looking to start a blog to write about various techy things I was working on and so I started looking for domains. Took a look, and sure enough signal0.com was available.

Of course I bought the domain, but then I never got around to actually writing that blog. Well here we are two years later. Lets see if I’ll keep up on this.