Script error: –le: binary operator expected

I'm just starting shell scripting and I got errors trying to execute the follow script:

I have the following script in a script.sh file

echo “enter a value” read n s=0 i=0 while [ $i –le $n ] do if [ `expr $i%2` -eq 0 ] then s= `expr $s + $i ` fi i= `expr $i + 1` done echo “sum of n even numbers” echo $s 

Script output:

akhil@akhil-Inspiron-5559:~/Desktop/temp$ chmod 755 script.sh akhil@akhil-Inspiron-5559:~/Desktop/temp$ ./script.sh “enter a value” 3 ./script.sh: line 5: [: –le: binary operator expected “sum of n even numbers” 0 

What is the source of the error I got?

2 Answers

The source of the error: [: –le: binary operator expected is the fact you are using the unicode version of – instead of the regular -

Note: The same apply for the unicode ” you are using instead of regular "

I've reformat your code to be as follows:

#!/bin/bash echo "enter a value" read -r n s=0 i=0 while [ $i -le "$n" ] do if [ "$(expr $i%2)" -eq 0 ] then s=$(expr $s + $i) fi i=$(expr $i + 1) done echo "sum of n even numbers" echo "$s" 

I made the following changes:

• Replaced the unicode version of chars you used
• Added #!/bin/bash
• Deleted space after the = sign
• Some extra improvements.

Yaron's answer helps you understand and remove the syntax errors.

My answer uses some 'nicer' syntax to do the same thing and something else, that might be what you want.

#!/bin/bash read -p "enter a number: " n s=0 i=1 j=0 while [ $i -le $n ] do if [ $(( i % 2 )) -eq 0 ] then s=$(( s + i )) j=$(( j + 1 )) fi i=$(( i + 1 )) # uncomment: remove the '#' from the beginning of the line # echo "i=$i" # uncomment to get debug output done #echo "n=$n" # uncomment to get debug output #echo "j=$j" # uncomment to get debug output #echo "s=$s" # uncomment to get debug output echo "Is this what you want?" echo "sum of $j even numbers ( <= $n ) = $s" echo "or is this what you want?" s=0 for ((i=1;i<=n;i++)) do echo -n "$(( 2*i )) " s=$(( s + 2*i )) done echo "" echo "sum of $n even numbers = $s" 

Running test examples,

$ ./sum-of-even-numbers enter a number: 3 Is this what you want? sum of 1 even numbers ( <= 3 ) = 2 or is this what you want? 2 4 6 sum of 3 even numbers = 12 $ ./sum-of-even-numbers enter a number: 4 Is this what you want? sum of 2 even numbers ( <= 4 ) = 6 or is this what you want? 2 4 6 8 sum of 4 even numbers = 20 $ ./sum-of-even-numbers enter a number: 6 Is this what you want? sum of 3 even numbers ( <= 6 ) = 12 or is this what you want? 2 4 6 8 10 12 sum of 6 even numbers = 42