[: -eq: unary operator expected

[: -eq: unary operator expected

The above error might come when we are using conditional operators to compare two values in a bash script. For example , conisder the following script to compare a user input number with a constant.

read $input if [ $input -eq 10 ] then echo "Equal" fi

The above script when executed will throw the error as listed before. The error in the program is use of $ while taking the input, that is the right way of using the read command is "read without a $ symbol before the name.

read input if [ $input -eq 10 ] then echo "Equal" fi

The second possible reason for the error could be not passing two values to compare for the operataor , for example the script below will also throw the same error as the operator "eq" has been given only a single operand.

read input if [ $input -eq ] then echo "Equal" fi

In the above example, we have missed passing the constant after the comparision opertaor.

Looking in the above two possibilities should fix the error.