I found this very cool but undocumented (why?) feature that you can
find the sender of a signal and pass a value (for realtime signals):
~/bin/ksh -c 'compound pc ; trap "pc.value=\${.sh.sig.value}
pc.pid=\${.sh.sig.pid}" RTMIN ; integer thispid=$$ ; kill -q 16#23456
-RTMIN $thispid & ; wait ; printf "%s\n" "${pc}"'
(
pid=984
value=16#23456
)
Now I thought this could be used create scripts which handle SIGCHLD
in an event-driven manner, but the concept doesn't work for SIGCHLD
traps:
~/bin/ksh -c 'compound pc=( integer value=-1 pid=-1 ) ; trap
"pc.value=\${.sh.sig.value} pc.pid=\${.sh.sig.pid} ; print trapCHLD"
CHLD ; integer thispid=$$ ; sleep 2 & ; wait ; printf "%s\n" "${pc}"'
trapCHLD
(
typeset -l -i pid=0
typeset -l -i value=0
)
Why does that happen?
Lionel
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