Software >

(on Wikipedia)

Process ID

Executing a command and learning it’s PID ∞

xterm & variable=$!
echo $variable

Learning a PID ∞

Maybe you can use wmctrl

ps ∞

(ps)

ps ax
ps alx

kill and pidof ∞

kill `pidof xterm`

kill -0 $SOMEPID 2> /dev/null
  if [ $? != 0 ]; then
  echo "It's not there"
fi

Fails:

if [ ! ps -C "$processname" > /dev/null ]; then
# exists
fi

if [ ! `ps -p $processnumber > /dev/null` ]; then
# exists
fi

In Bash and Zsh ∞

(Bash, Zsh)

echo $$

Also $PPID

Do this to learn your process too!

ps -fp $$

in Ruby ∞

(Ruby)

$$

xtoolwait ∞

(xtoolwait)

xtoolwait -pid <application>