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Check for Empty Command Argument


 
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# 1  
Old 09-19-2007
Check for Empty Command Argument

I have a script that when called can have 1 or 2 command arguments. If only 1 command argument is passed into the script how can I check that the second argument is null? I am working in Korn shell in a UNIX environment.


Example of script call with 2 arguments:
Code:
% statreport 0300 1430


Example of script call with 1 argument:
Code:
% statreport 0300

# 2  
Old 09-19-2007
Use $# to check for the number of arguments passed. [ -z "$#" ] to check for null arguments.
# 3  
Old 09-19-2007
The user knows to call the script with either 1 or 2 command arguments. Depending on the call I need the script to perform different operations. How exactly would I check if the second command argument is null?
# 4  
Old 09-19-2007
You can try doing
if [ "$#" - ne 2 ] then

do something else.

fi

So if the first argument is passed to the script then there is no problem. If the second argument is not supplied then do something else. Hope that helps a bit.
# 5  
Old 09-19-2007
Quote:
Originally Posted by Nysif Steve
The user knows to call the script with either 1 or 2 command arguments. Depending on the call I need the script to perform different operations. How exactly would I check if the second command argument is null?

Use test (a.k.a. [):

Code:
if [ -z "$2" ]
then ## Second argument is empty
   : do something
else
   : do something else
fi

# 6  
Old 09-19-2007
Still the same error. Here is a larger portion of the code:

Code:
        ((startTime= `perl -e 'print time;'`))
	((currentTime= $startTime))
	((executeTime= $startTime))
	tempTime=`date +%H%M`


	# Check if the second command argument is exists.
	if[ "$#" <  2 ]
	then
		((endTime = $startTime + 28800))		# Add 8 hours = 28800 seconds

	# If The second command line argument isn't empty
	else
		((temp = `expr $2 - $tempTime`))
		if[ $temp < 0 ]					# If temp is negative convert it to positive
		then
			((tempHour = temp / 100))
			((tempHour = tempHour * -3600)) 	# Multiply hours by -3600 seconds per hour to make positive
			((tempMin = temp % 100))
			((tempMin = tempMin * -60))		# Multiple minutes by -60 seconds per minute to make positive
			

		else
			((tempHour = temp / 100))
			((tempHour =  tempHour * 3600)) 	# Multiply hours by 3600 seconds per hour
			((tempMin = temp % 100))
			((tempMin =  tempMin * 60))		# Multiple minutes by 60 seconds per minute
		fi

		((endTime = $endTime + $tempHour + $tempMin))
	fi

# 7  
Old 09-19-2007
NySif,

Not sure if that is valid shell syntax "if[ "$#" < 2 ]"

Maybe you can try if[ "$#" -lt 2 ]
 

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