Having explained all this for your understanding, here is the actual
problem: Logging never really starts before I explicitly attach the
detached session at least once. After the login message has been saved
to the logfile, nothing else is logged anymore. Attaching and detaching
the session again fixes this behaviour.
Sample script:
#!/bin/sh
# start clean session
DIR=/var/tmp/fritzterm
rm -rf $DIR
mkdir $DIR
cd $DIR
# create detached screen session with auto-logging
screen -dm -L -S fritzterm
# maybe decreasing the flush interval helps?
screen -S fritzterm -X logfile flush 0
# issue remote command inside the session
screen -S fritzterm -X exec ls -l /
# wait a moment, then check log file's content
sleep 2
cat /var/tmp/fritzterm/screenlog.0
Unfortunately the effect is as described above. No logging whatsoever,
no matter hown many commands are issued to the screen session. Attaching
the session shows the same: nothing except the shell's welcome message
is there. But from that moment on evetything is neatly logged, no matter
if the session is attached or detached.
How can I solve this problem?