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On Tue, 2 May 2006, Hans-Werner Hilse wrote: |
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|
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>> Based on the suggestions of Uwe and Vladimir, I tried |
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>> trap 'pkill -TERM -P $$; kill -s TERM $$' TERM |
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>> <do something> |
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>> . /path/to/child.sh |
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>> <do something else> |
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>> Doesn't work, yet. Note that child.sh is a shell script that may execute |
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>> some other command (like rsync), so the "." by itself may not be enough. |
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> |
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> This can't work because of this (man bash): |
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> --snip |
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> If bash is waiting for a command to complete and receives a signal for |
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> which a trap has been set, the trap will not be executed until the |
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> command completes. |
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> --snip |
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> |
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Oops...! |
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> What instead works (just tested): |
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> --snip |
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> #!/bin/sh |
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> COMMAND="sleep 120" |
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> |
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> # First we background: |
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> $COMMAND & |
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> # Save the PID |
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> CHILDPID=$! |
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> # Trap the signal: |
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> trap "kill -TERM $CHILDPID" TERM |
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> # And wait for the Child to finish: |
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> wait $CHILDPID |
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> # reset signal handling: |
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> trap - TERM |
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> --snip |
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> |
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Backgrounding is really not an option. The whole setup is to be supervised |
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by daemontools. |
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> Note that the code could hit a racing condition and should therefore |
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> not carelessly run by root on a machine with untrusted users. This is: |
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> The process may have finished before setting the signal handler. |
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> Other processes *might* reuse the PID afterwards and might get |
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> sig-TERM-ed until resetting the signal handler again. Probably a minor, |
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> depending on the script's usage. |
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> |
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Precisely the kind of thing I want to avoid. I think I need to |
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reformulate my setup. |
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> |
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Thanks. |
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|
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Jorge Almeida |
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-- |
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