> Can somebody explain this behavior? Something about process groups or
> controlling terminal requiring a shell process to go between the
> 'screen' and the soft IOC?
You don't need a shell, just a terminal. Screen really wants to be
associated with a terminal, for obvious reasons. The exception to this is
when it is running "detached".
So, the key is to *always* start screen detached [-d -m]. You can then
"re-attach" at any time by using "screen -r" (as the user owning the screen
process). Output from the IOC will be buffered by screen while detached
(up to a user-definable number of lines) and can be reviewed later [see
"scrollback buffer"]. When done, you detach it again [C-a C-d].
This approach works both from startup scripts and from the command line, so
you can use the same "boot" script for both.
Here's our init.d script [RedHat 7.3]. It assumes you don't have any other
"screen" processes running:
================
#!/bin/bash
# init file for EPICS Linux IOC
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0
# source function library
. /etc/init.d/functions
RETVAL=0
prog="epicsIoc"
host=$(hostname -s)
start() {
echo -n $"Starting $prog: "
daemon --user epics /home/locus/epics/IOC_runtime/${host}App/current/BOOT_ioc${host}
RETVAL=$?
echo
touch /var/lock/subsys/epicsIoc
return $RETVAL
}
stop() {
echo -n $"Stopping $prog: "
killproc SCREEN
RETVAL=$?
echo
rm -f /var/lock/subsys/epicsIoc
return $RETVAL
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
status)
status SCREEN
RETVAL=$?
;;
*)
echo $"Usage: $0 {start|stop|status|restart}"
RETVAL=1
esac
exit $RETVAL
==================
The IOC script is just this:
==================
#!/bin/bash
cd {IOC directory}
screen -d -m iocXXXX XXXX.cmd
----
Brian McAllister Senior Software Engineer
[email protected] MIT-Bates Linear Accelerator
(617) 253-9537 Middleton, MA
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