85 lines
1.7 KiB
Bash
Executable File
85 lines
1.7 KiB
Bash
Executable File
#!/bin/bash
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#
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# Copyright (c) International Business Machines Corp., 2005
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# Author: Ram Pai (linuxram@us.ibm.com)
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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lockfile="/.nslock"
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SUCCESS=0
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FAIL=1
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otherpid=
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startparent()
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{
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rm -f $lockfile
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echo $$ >| ${lockfile}parent
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while [ 1 ]
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do
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otherpid="$(cat ${lockfile}child 2> /dev/null)"
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if [ -n "$otherpid" -a -d /proc/$otherpid ]
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then
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return
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fi
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done
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}
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startchild()
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{
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rm -f $lockfile
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echo $$ >| ${lockfile}child
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while [ 1 ]
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do
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otherpid="$(cat ${lockfile}parent 2> /dev/null)"
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if [ -n "$otherpid" -a -d /proc/$otherpid ]
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then
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return
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fi
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done
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}
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iamgoingahead()
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{
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while [ 1 ]
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do
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if [ ! -d /proc/$otherpid ]
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then
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return $FAIL
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fi
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str=`cat $lockfile 2> /dev/null`
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pid=$(echo $str | awk '{print $1}')
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error=$(echo $str | awk '{print $2}')
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if [ "$pid" == "$$" ]
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then
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return $error
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fi
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sleep 1
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done
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}
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goahead()
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{
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set -x
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ret=$SUCCESS
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if [ -n "$1" ]
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then
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ret=$1
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fi
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echo "$otherpid $ret" >| $lockfile
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set +x
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}
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