I have a script going through ELF files and finding which of them refer
to non-existing shared libraries. After finding the files, it proceeds
by checking which package they belong to, which is an expensive
operation, so it is done in a "coproc" co-process.
The main loop knows when all the files have been sent to the "checker"
co-process and sends a special filename as an "exit" command. In the
original design, "checker" would immediately exit upon seeing this
special command. On unix-like systems, "exit" means "flush all output
and terminate afterwards", but on bash-4.0.24(1)-release a co-process
seems to exit somewhere in between.
I need to resort to the following workaround:
coproc checker {
checker_fail_cnt=0
while true
do
[ ${checker_fail_cnt} -gt 0 ] && {
let ++checker_fail_cnt
echo_v 3 "checker: checker_fail_cnt: ${checker_fail_cnt}"
[ ${checker_fail_cnt} -gt ${checker_fail_cnt_max} ] && break
sleep 1
continue
}
read dafile
case "_${dafile}" in
"_${checker_exit}")
echo_v 3 "checker: shutting down on '${checker_exit}'"
echo "${checker_exit}"
let ++checker_fail_cnt
continue
;;
esac
# do stuff with any file names sent on stdin ...
done
exit 0
}
It delays exiting for ${checker_fail_cnt_max}+1 seconds, while the main
process hurries to read out everything "checker" has already sent.
If I simply do this:
coproc checker {
while true
do
read dafile
case "_${dafile}" in
"_${checker_exit}")
echo_v 3 "checker: shutting down on '${checker_exit}'"
echo "${checker_exit}"
break
;;
esac
# do stuff with any file names sent on stdin ...
done
exit 0
}
and let the main process read until it sees "${checker_exit}" coming
back, it will almost never receive it. Instead, its "read -u
${checker[0]}" will return an exit code of one eventually without having
read all that "checker" ever sent.
Since my workaround will leave a useless process sitting for a while or
until killed explicitly, I'd like to get rid of it. Using a timeout in
the main process is equally unacceptable: it slows down the final steps
and it doesn't guarantee receiving a complete output line. Also, this
application is quite simple: there must be an output from "checker" for
every input to it. In the future I may have much looser coupling
between processes.
Is there a better workaround until this is fixed?
regards, clemens
