Shell Programming and Scripting

Hi All,

I am new to unix shell scripting,
in the below script "num" is an input file which contains a series of numbers example :
2
3
5
8

I want to add the above all numbers and want the result finally outside the while loop. it prints the value zero instead of the actual expected result. I have given export i within a loop but it did not work. any idea?

Code:

 
#!/bin/sh
#set -x
i=0
while read line
do
i=`expr $i + $line`
echo $i
export i
done< num
echo $i

BUT the below gives the expected output

Code:

#!/bin/sh
#set -x
i=0
until [ $i -eq 10 ]
do
i=`expr $i + 1`
done

echo "$i"

This works

i=0;
while read line
do i=`expr $i + $line`
echo $i
done < add
echo "Final :$i"


cheers,
Devaraj Takhellambam

Well, the script should work as expected, unless "num" is a 0-byte file. Did you check that ? Otherwise, what value is displayed per loop iteration ?

As mentioned by the other poster, the "export" command is not really needed.

HTH,
tyler_durden

Here is a file "num" and its content
# more num
1
2
3
6
5
3
# more add.sh
#!/bin/sh
#set -x
i=0
while read line
do i=`expr $i + $line`
done < num
echo "Final :$i"

# ./add.sh
Final :0
#

I changed the script as you said, but the output was zero. I need to get the total sum value outside the while loop.

Hello nagnatar,

What happens in last script is that if there is any blank line in "num" file then the expression i=`expr $i + $line` goes as i=`expr 10 + ` which is a syntax error.

so there are few solutions to but here are few.
1. delete all blank line or
2 . include a condition in script which will test either the line is blank or not.

#!/bin/sh
#set -x
i=0
while read line
do
echo --------- $i
if [ "$line" ]; then
i=`expr $i + $line`
fi
done < num
echo - $i




Contents of the file is
1
2
3
4
5
6




~
~
~
~
~
~
~

Hello nagnatar,

What happens in last script is that if there is any blank line in "num" file then the expression i=`expr $i + $line` goes as i=`expr 10 + ` which is a syntax error.

so there are few solutions to but here are few.
1. delete all blank line or
2 . include a condition in script which will test either the line is blank or not.

#!/bin/sh
#set -x
i=0
while read line
do

if [ "$line" ]; then
i=`expr $i + $line`
fi
done < num
echo - $i




Contents of the file is
1
2
3
4
5
6




~
~
~
~
~
~
~


On executing the script output for the num file is 21

Pradeep, There is no blank line in "num" file.my question is that why am not getting total sum value outside the while loop.? is it due to scope of the variable? but am getting value of the variable outside the 'until' loop. have a look at the script i posted in my first post. Thanks!