BASH If Command Not Found-CodePudding

I have a slight problem with my BASH script that I do not know the cause.

Please take a look at this simple script.

#!/bin/bash
# Given two integers X and Y. find their sum, difference, product, and quotient

# Constraints
# -100 <= X,Y <= 100
# Y != 0

# Output format 
# Four lines containing the sum (X Y), difference (X-Y), product (X x Y), and the quotient (X // Y) respectively.
# (While computing the quotient print only the integer part)

# Read data
echo "Please input for x and y!"
read x
read y

declare -i MIN=-100
declare -i MAX=100


# Checks if the valued read is in the constraints
if [ $x -gt $MAX ] || [ $x -lt $MIN ];
then
    echo "Error!"
    exit 1;
elif [ $y -gt $MAX ] || [$y -lt $MIN ] || [$y -eq 0];
then
    echo "Error"
    exit 1;
else
    for operator in {" ","-","*","/",}; do echo "$x $operator $y" | bc; done
fi

The output of the script above is as follow.

Please input for x and y!
1
2
worldOfNumbers.sh: line 26: [2: command not found
worldOfNumbers.sh: line 26: [2: command not found
3
-1
2
0

As you can see, there is this [2: command not found. I believe there is something wrong with my syntax however I feel like I have typed the right one.

p.s. I use Oh My ZSH to run the program. I've also tried running in VS Code however the same thing arise.

Thank you for the help.

CodePudding user response：

If you put your code through shellcheck, you'll see that it is due to the lack of spaces between your variable and your bracket. Bash is a space oriented language, and [ and ] are commands just like echo or printf.

Change

elif [ $y -gt $MAX ] || [$y -lt $MIN ] || [$y -eq 0];

elif [ $y -gt $MAX ] || [ $y -lt $MIN ] || [ $y -eq 0 ];
                         ^                  ^        ^

Arrows added to show where spaces were added.

You can see that [ is a command if you run this at your bash prompt:

$ which [
[: shell built-in command

Because you do not have a space between [ and 2, bash assumes that you are trying to run a command called [2 and that command does not exist, as seen by your error message.

CodePudding user response：

I seemed to fix it. Here is the code.

#!/bin/bash
# Given two integers X and Y. find their sum, difference, product, and quotient

# Constraints
# -100 <= X,Y <= 100
# Y != 0

# Output format 
# Four lines containing the sum (X Y), difference (X-Y), product (X x Y), and the quotient (X // Y) respectively.
# (While computing the quotient print only the integer part)

# Read data
echo "Please input for x and y!"
read x
read y

declare -i MIN=-100
declare -i MAX=100


# Checks if the valued read is in the constraints
if [ "$x" -gt $MAX ] || [ "$x" -lt $MIN ]
then
    echo "Error!"
    exit 1
elif [ "$y" -gt $MAX ] || [ "$y" -lt $MIN ] || [ "$y" -eq 0 ]
then
    echo "Error"
    exit 1
else
    for operator in {" ","-","*","/",}; do echo "$x $operator $y" | bc; done
fi

There should be a space inside the [ expression ]. Pretty interesting!