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From: Devin Teske <dteske@vicor.com>
To: Aryeh Friedman <aryeh.friedman@gmail.com>
In-Reply-To: <AANLkTi=NJA4by3Pnv7f=KOh-R+STq_aLiuS9K4FFO0_7@mail.gmail.com>
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Date: Thu, 27 Jan 2011 17:38:48 +0000
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Cc: Devin Teske <dteske@vicor.com>,
	FreeBSD Mailing List <freebsd-questions@freebsd.org>
Subject: Re: OT: How to set a timeout for a process
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On Thu, 2011-01-27 at 03:37 -0500, Aryeh Friedman wrote:

> I have a script that may or not hang (the reasons why it hangs are
> unimportant here) and need to call it from an other script and need to
> say if it hangs to give up after X seconds and just continue the
> script (no harm done if it fails)


#!/bin/sh
# -*- tab-width:  4 -*- ;; Emacs
# vi: set tabstop=4     :: Vi/ViM
############################################################ GLOBALS

# Global exit status variables
SUCCESS=0
FAILURE=1

############################################################ FUNCTIONS

# timeout_watcher $nsecs
#
# No need to call directly. Used by eval_timeout in the following
manner:
#     eval_timeout $nsecs $cmd ... | timeout_watcher $nsecs
#
timeout_watcher()
{
    local timeout="$1" tPID tALIVE

    read tPID
    while :; do
        kill -INFO $tPID 2> /dev/null || break
        read -t "$timeout" tALIVE
        if [ ! "$tALIVE" ]; then
            # The SIGINFO trap didn't respond in the given timeout...
            # ... assume the sub-shell has hung and kill it.
            kill -9 $tPID
            break
        fi
        sleep $timeout
    done
}

# eval_timeout $nsecs $cmd ...
#
eval_timeout()
{
    local timeout="$1"

    [ "$timeout" ] || return $FAILURE
    shift

    cat <<-EOF | sh -T | timeout_watcher $timeout
        trap 'echo still alive' INFO
        echo \$\$
        eval "$@" 2>&1
    EOF
}

############################################################  MAIN

eval_timeout "$@"

    



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