License: (CC 3.0) BY-NC-SA
an amazing program
$ cat truth
#! /usr/bin/env python
while True:
print "God's in his heaven. All' right with the world."
print "-- Robeert Browning"
now, i want this program can be used everywhere
$ chmod u+x truth
$ sudo mv truth /usr/bin
does it work?
$ truth
God's in his heaven. All' right with the world.
-- Robeert Browning
God's in his heaven. All' right with the world.
-- Robeert Browning
...
the truth is going crazy and won’t stop, so press CTRL+C to stop it
a system service
now i want it to be a system service, but, firstly, what is a system service?
$ cat /etc/init.d/truth
### BEGIN INIT INFO
# Provides: truth
# Required-Start: $local_fs $remote_fs
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop:
# Short-Description: truth
# Description: a simple truth
### END INIT INFO
set -e
case "$1" in
start|restart)
echo "yeah, i'm alive!"
;;
stop)
echo "oh no! i don't want to die!"
;;
*)
echo "Usage: truth {start|stop|restart}" >&2
exit 1
;;
esac
exit 0
$ ls -l /etc/init.d/truth
-rwxr--r-- 1 root root 226 Mar 1 19:31 /etc/init.d/truth
$ sudo service truth start
yeah, i'm alive!
$ sudo service truth stop
oh no! i don't want to die!
so i just create a simple bash script which accept some regular arguments for service. now i can use the truth just as a service.
but i don’t want the useless output, i want the TRUTH, so i change the /etc/init.d/truth, remove the echo statement and replace it by:
start|restart)
truth > /tmp/truth &
;;
stop)
echo "oh no! i don't want to die!"
;;
you know what would happen, so i just show you:
$ sudo service truth start
ah ha, it quiet, but i know there is a background thread which will silently eat my entire disk, so i check it
$ tail -f /tmp/truth
God's in his heaven. All' right with the world.
-- Robeert Browning
God's in his heaven. All' right with the world.
-- Robeert Browning
...
no, i want to stop it, so i press CTRL+C, but it doesn’t work, the print of tail -f dispeared but the thread is still there, and may be it can:
$ sudo service truth stop
oh no! i don't want to die!
$ tail -f /tmp/truth
God's in his heaven. All' right with the world.
-- Robeert Browning
God's in his heaven. All' right with the world.
-- Robeert Browning
...
shit! so i must kill it by
$ ps aux | grep truth
$ sudo kill 1219
how can i stop it by sudo service truth stop? oh, i’m so tired, may be next time i will tell you