Shell Programming and Scripting

Hi all,
I am trying to figure out a method to flag an error if a file has not arrived in a certain directory within 24 hrs of the last one arriving.
I am currently writing the time to a file when a file is recieved. I then want to check for a new file reguarly but flag an error if it has been over 24 hrs since a file was received. However i cannot work out how to test for a 24 hour period as the script will be run at irregular intervals.
Any ideas?

Thanks

time_diff (){
start_mins=`echo "$1"|awk -F":" '{print $1*60+$2}'`
end_mins=`echo "$2"|awk -F":" '{print $1*60+$2}'`
((elapsed_mins = $end_mins - $start_mins))

if [ "$elapsed_mins" -lt 0 ]
then
((elapsed_mins += 1440))
fi

if [ "$elapsed_mins" -gt 59 ]
then
print $((elapsed_mins / 60))
fi
}

last_time=`ls -lrt|tail -1|awk '{print $8}'`
curr_time=`date "+%k:%m"`
time_diffrence=`time_diff $last_time $curr_time`

if [ "$time_diffrence" -lt "24 ]
then
do whatever you want
fi

or simply you can use find command to see whether you have any file which is older than 24 hrs..

You can jsut use the find command to handle this...

Code:

find directory -name "filename" -type f -mtime -1

or

Code:

find directory -name "filename" -type f -mmin -1440