1 #!/bin/bash 2 3 lockfile="/.nslock" 4 SUCCESS=0 5 FAIL=1 6 otherpid= 7 startparent() 8 { 9 rm -f $lockfile 10 echo $$ >| ${lockfile}parent 11 while [ 1 ] 12 do 13 otherpid="$(cat ${lockfile}child 2> /dev/null)" 14 if [ -n "$otherpid" -a -d /proc/$otherpid ] 15 then 16 return 17 fi 18 done 19 } 20 21 startchild() 22 { 23 rm -f $lockfile 24 echo $$ >| ${lockfile}child 25 while [ 1 ] 26 do 27 otherpid="$(cat ${lockfile}parent 2> /dev/null)" 28 if [ -n "$otherpid" -a -d /proc/$otherpid ] 29 then 30 return 31 fi 32 done 33 } 34 35 iamgoingahead() 36 { 37 while [ 1 ] 38 do 39 if [ ! -d /proc/$otherpid ] 40 then 41 return $FAIL 42 fi 43 str=`cat $lockfile 2> /dev/null` 44 pid=$(echo $str | awk '{print $1}') 45 error=$(echo $str | awk '{print $2}') 46 if [ "$pid" == "$$" ] 47 then 48 return $error 49 fi 50 sleep 1 51 done 52 } 53 54 goahead() 55 { 56 set -x 57 ret=$SUCCESS 58 if [ -n "$1" ] 59 then 60 ret=$1 61 fi 62 echo "$otherpid $ret" >| $lockfile 63 set +x 64 } 65
