Time Difference

Shell Programming and Scripting
1

Is this way of finding the time difference a correct way of doing it or is it error-prone.

#****Check if lastrun exist. If exists check if the difference is 1 hour or not and act accordingly***********************
if [ -f $LOG_DIR/lastrun ]; then
	lastrun_time=`cat $LOG_DIR/lastrun`
	curr_time=`date +%s`

	#Here we are checking if the last run was within the last hour, if true we simply exit without running.	
	if [ $((curr_time-lastrun_time)) -le 3600 ]; then
		#echo "File is being run within an hour of last run.exiting."
		exit
	else
		#Removing last run, if the last run is beyond an hour we remove the file and rerun the grep.
		rm -f LOG_DIR/lastrun
	fi	
fi

TIA
Sreekanth

2 
$(($curr_time - $lastrun_time))

Please use code tags.

3

What does $LOG_DIR/lastrun contain ?

--
Actually, POSIX compliant shells should not require dollar signs when using integers in an arithmetic expansion:

Shell Command Language: 2.6.4 Arithmetic Expansion

1 Like
4

Scutinizer,

lastrun contains the time when the script was last run, the same as `date +%s`

Tks,
Sreekanth

5

If it contains epoch time then I would think this is a valid way of finding the difference.

I noticed a $-sign is missing

rm -f LOG_DIR/lastrun

It is a good practice to use double quotes around variable reference:

rm -f "$LOG_DIR/lastrun"

Although I am sure the path to your log dir will not contain spaces or funny characters..

You might like to use something like:

exit 1

So you have a return code..

1 Like