shell scripting EXPR syntax error

Question

I am getting a syntax error in the following code. I am trying to print the squares of a number n.

#!/bin/sh

echo "Enter a number n to print squares : "
read num

i=1

while [ $i -le $num ]
do

    echo $(expr $i * $i)
    i=$(expr $i + 1)

done

echo "Done with Script"

Can someone tell me whats wrong with the code? Thank you guys in advance.

There is a syntax error in your code. Is that all you want to tell us? — Yunnosch, Jan 25 '18 at 08:02

score 0 · Answer 1 · answered Jan 25 '18 at 08:00

0

#!/bin/sh

echo "Enter a number n to print squares : "
read num

i=1

while [ $i -le $num ]
do

    echo $(expr $i \* $i)
    i=$(expr $i + 1)

done

echo "Done with Script"

Shield * symbol.

answered Jan 25 '18 at 08:00

Viktor Khilin

1,760
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1

Would you like to give more explanation? Why is it necessary to escape/shield the asterisk? – Yunnosch Jan 25 '18 at 08:01
1

Because it's a wildcard character to the shell. Equivalently, quote it. Better yet, don't use `expr` (and don't tag questions as [tag:bash] if they are not about Bash at all; but if you do have access to Bash, that's a good way to avoid `expr` completely). – tripleee Jan 25 '18 at 08:03
Yes Why do we need to shield '*' ? – Abhishek Gangadhar Jan 25 '18 at 08:03
@tripleee What are the alternatives of expr? – Abhishek Gangadhar Jan 25 '18 at 08:04
You posted this question with the tags [tag:bash] and [tag:linux] so I assume you have Bash. Read the man page, look for "arithmetic". – tripleee Jan 25 '18 at 08:05
@AbhishekGangadhar you can write `i=$(($i + 1))`; `echo $(($i * $i))` – Viktor Khilin Jan 25 '18 at 08:05
@ViktorKhilin Thank you :) – Abhishek Gangadhar Jan 25 '18 at 08:08

shell scripting EXPR syntax error

1 Answers1