Write a PID file manually from Bash script
Solution 1:
You can easily run the process in the background with "&", then get the PID of the background process using "$!"
#!/bin/bash
long_running_tool &
echo $! > pid_file
Then, optionally, wait $! if you want the shell to block until the process completes execution.
Solution 2:
#!/bin/bash
echo $$ > fooapp.pid
exec fooapp
As mentioned earlier, exec replaces bash with the specified program, retaining the PID.