COMP111 : Quiz 3
Shell Programming

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1) What is wrong with the following shell program? 

# /bin/sh
echo "Enter name: "
read $name
echo "How many girlfriends do you have? "
read $number
echo "$name has ***$number*** girlfriends:)"



Answers: 
1) Delete "$" in "read $name" and "read $number"
2) # /bin/sh
should be:
#!/bin/sh

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2) What is wrong with the following shell program? 

#!/bin/sh
echo "Enter height of parallelogram: "
read height
echo "Enter width of parallelogram: "
read width
area = 'expr $height * $width'
echo "The area of the parallelogram is $area"



Answers: 
1) Need backslash before star in multiplication:
expr $height \* $width
2) Cannot have spaces in "area = ", 
should be: "area="
3) area = 'expr $height \* $width'
should be with backquotes:
area = `expr $height \* $width`

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3) What is wrong with the following shell program? 

#!/bin/sh
user=`whoami`
if[$user = "gates"] 
	echo "Hi Bill!"
else
	echo "Hi user!"
fi


Answers: 
1) echo "Hi user!" should be:
	echo "Hi $user!"
2) Need spaces in if: 
	if [ $user = "clinton" ] 
3) Need then after if:
	#!/bin/sh
	user=`whoami`
	if [ $user = "clinton" ] 
	then
		echo "Hi Bill!"
	else
		echo "Hi $user!"
	fi

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4) What is wrong with the following shell program? 

#!/bin/sh
echo -n "Enter full name and student ID: "
read name id
echo "$name has id#$id"



Answer: 
read will only put first name into $name 
(and rest into $id). Instead:
#!/bin/sh
echo -n "Enter full name: "
read name
echo -n "Enter student id: "
read id
echo "$name has id#$id"

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5) What is wrong with the following shell program? 

#!/bin/sh
users=`who | wc -l`
if [ $users >= 4 ] 
then
	echo "Heavy load!"
elif[ $users > 1 ]
	echo "Medium load"
else
	echo 'Just me!'
fi

Answers: 
1) Need space after elif:   elif [ $users > 1 ] 
2) No ">=" and ">". Should be: 
	if [ $users -ge 4 ]
3) Need then after elif:
	#!/bin/sh
	users=`who | wc -l`
	if [ $users -ge 4 ] 
	then
		echo "Heavy load!"
	elif [ $users -gt 1 ]
	then
		echo "Medium load"
	else
		echo 'Just me!'
	fi
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6) What is wrong with the following shell program? 

#!/bin/sh
resp="no"
while [ $resp -ne "yes" ]
	echo -n "Wakeup [yes/no]? "
	read resp
endwhile


Answers: 
1) while [ $resp -ne "yes" ]
only works for numerical comparisons, use:
while [ $resp != "yes" ]
2) endwhile should be done
3) Need do after while:
	#!/bin/sh
	resp="no"
	while [ $resp != "yes" ]
	do
		echo -n "Wakeup [yes/no]? "
		read resp
	done