# We will first learn how to run a process in the background and how
# to get its process ID (pid). The first step is running a command
# without waiting for the result, which is achieved by ending the
# command with a single ampersand, like this:

while true; do sleep 1; echo .; done &

# Now the entire compound command is running in a separate process
# (the shell has forked): the parent processes continues to execute
# this script (i.e. the commands below) while the child runs the
# command above (it runs in the background, but it can still print
# to the terminal). To do anything useful with the running process,
# we need to learn its process identifier, which is stored in the
# shell variable ‹$!›.

child=$!
echo $child

# Then we wait a bit, so that the loop above can print a few lines.
# The ‹sleep› command, as you probably figured out by now, does
# nothing for a given number of seconds (5 in this case).

sleep 5

# Now we request that the child process terminates. This is a ‘nice’
# request, in the sense that the operating system notifies the
# process that the user asked for its termination. The process may
# or may not honour the request (it usually will, but it may perhaps
# try to clean things up before terminating).

kill $child

# As usual, you can look up ‹kill› in the manual. That's it, we will
# look at a few more process management commands now:
#
#    $ micro ps.sh