Date and time difference - UNIX for Dummies Questions & Answers

risshanth · #1 10-07-2008

Hi,

I am starting a process at 9 pm today and want to exit the process by 5am, the next day. Every day at 9pm the shell script will be invoked by autosys.
But how can i monitor in my script for 5 am and stop the process ?

there may be a case where the script can start at 4.59 am and complete by even 6.00 am. So checking for (if current time >= 5 am ) will also wont work. Is there any function like date_diff or something else ?? How this can be acheived.

Risshanth

jim mcnamara · #2 10-07-2008

You want the script to stop itself after 8 hours or 28800 seconds. Here is one somewhat clunky way -

Code:

#!/bin/ksh
#  script1.shl
secs()
{
   perl -e 'print time;'
}
start=$(secs)
stoptime=$(( start + 28800))
now=$(secs)
while [[ $now -lt stoptime ]]
do
      sleep 1
      now=$(secs)
done
kill -USR1 $PPID
exit

main script

Code:

#!/bin/ksh
trap "sleep 1; exit" USR1 
script1.shl &

#.............your code goes here..........

risshanth · #3 10-07-2008

The time calculating stuff i clear. What does the following does:

trap "sleep 1; exit" USR1 in the main code.

Please explain this in detail.

Thanks....

jim mcnamara · #4 10-07-2008

When the child process gets past the time barrier it sends a SIGUSR1 to the parent. The trap in the parent grabs the signal (trap) sleeps long enough for the child to exit, then exits itself.

trap "command[s] to execute" signalname

to see all signals for your system try

Code:

kill -l

the -l is a lowercase L

fpmurphy · #5 10-07-2008

If you are using ksh93, you can use the alarm mechanism to simplify coding as shown in the following simple example

Code:

!#/usr/bin/ksh

# abort after 10 seconds
alarm -r timedout +10

timedout.alarm()
{
    print "Exceeded allowed time.  Aborting script ........"
    kill -9 $$
}

read dummy         # dummy wait - press ENTER to exit
exit 0

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