# Now that we know how to run a process from shell, we will look at
# a few more commands that work with processes. So far, we have only
# seen ‹kill›, which, given a process ID, sends a signal to the
# process. You can learn more about signals in ‹man 7 signal› --
# unfortunately, we won't have time to get into details in the
# seminar.

# First we will create a process and get its pid, like we did
# before:

chmod +x spin.sh
./spin.sh &

set -x

pid=$!

# The first command that I want to show you is ‹pgrep›, which allows
# you to find processes by looking at the commands those processes
# are executing. Of course, you can look at ‹man pgrep›. Without
# ‹-f›, it checks only the command itself, with ‹-f› it will also
# match on the command line arguments. To make things a little more
# complicated, executable scripts sometimes have their filename as
# the command name, and sometimes the interpreter name, depending on
# the operating system. On ‹aisa›, it is the former, so the first
# command will work as we expect.

pgrep spin.sh
pgrep -f spin.sh

# The ‹pgrep› command has a companion called ‹pkill›, which does the
# same thing but instead of printing the process id's of the
# matching processes, it kills them (sends them a ‘please terminate’
# signal, also known as ‹TERM›). Killing processes forcibly can be
# done with the ‹-KILL› switch to either ‹kill› or ‹pkill›. It is
# usually better to not use ‹-KILL›.

# The last user command for process management that you need to know
# is ‹ps›, which is short for ‘processes’ and simply prints a list
# of all processes. By default, only interactive processes owned by
# you are shown:

ps

# If we want to see more details, we can add ‹u› to the options.
# Notice that unlike most other unix programs, the switches to ‹ps›
# can be specified without the dash.

ps u

# But if you are more comfortable with the dash, you can have it,
# too:

ps -u # the same as the previous command

# We can request to also see processes that do not have a
# controlling terminal.

ps -x

# And finally, we can also request to see all the processes in the
# system with ‹ps -a›, but we won't run that in the script because
# there are many. You can try running it by hand if you like.
# Another command to try yourself would be ‹top›, which
# interactively shows current processes in the system and tells you
# how much CPU and memory they use.

# Okay, let's wait for a bit to check our process is running. Be
# sure to notice our process in the process listings from ‹ps›.

sleep 3
kill $pid

# Let's do an exercise, ‹1.txt›.