#! /bin/sh

# Question 5:

# Modify your answer to question 4 so that:
# o if the lockfile exists, the program will print an error
#   message and terminate;
# o if the lockfile doesn't exist, then the program creates it,
#   and makes sure that the lockfile was successfully created;
# o when the program exits normally, it will remove the lockfile.

prog=$(basename $0)
uid_num=$(id -u)

lockfile="/tmp/${prog}.lock"
[ "$uid_num" -eq 0 ] && lockfile=/var/lock/subsys/${prog}.lock
if [ -e "$lockfile" ]
then
    echo "lockfile exists"
    exit 1
else
    touch $lockfile
    [ -e $lockfile ] || { echo "$prog: cannot create $lockfile"; exit 1; }
fi

# just to help in testing:
sleep 60
rm -f $lockfile