How to get the pid of the last executed command in shell script?

The PID of the last executed command is in the $! shell variable:

my-app &
echo $!

Get PID:

#!/bin/bash
my-app &
echo $!

Save PID in variable:

#!/bin/bash
my-app &
export APP_PID=$!

Save all instances PID in text file:

#!/bin/bash
my-app &
echo $! >>/tmp/my-app.pid

Save output, errors and PID in separated files:

#!/bin/bash
my-app >/tmp/my-app.log 2>/tmp/my-app.error.log &
echo $! >>/tmp/my-app.pid

echo "my-app PID's: $(cat /tmp/my-app.pid)"

Try something like

pidof my_app >> /tmp/my_app.pid

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