Check whether one number equals another number in bash

Question

I've been trying to compare whether two numbers in Bash are equal (and print a message if they are equal), but I'm getting some strange error messages for this simple program:

#!/bin/bash

fun2 (){
    $x = 3
    //#prog.sh: line 4: =: command not found
    if [x == 3]
        then 
    //#prog.sh: line 6: [x: command not found
            echo "It's 3!"
    fi
}
fun2

The corresponding errors are shown below the lines that caused those errors.

question from:https://stackoverflow.com/questions/15867813/check-whether-one-number-equals-another-number-in-bash

Answer 1

It must be:

 if [ $x -eq 3 ]; then .....

if you prefer a more readable and self-explanatory code, use this syntax:

 if test $x -eq 3; then .....

explanation:

To compare integers you must use those operators (copied from man test):

   INTEGER1 -eq INTEGER2
          INTEGER1 is equal to INTEGER2

   INTEGER1 -ge INTEGER2
          INTEGER1 is greater than or equal to INTEGER2

   INTEGER1 -gt INTEGER2
          INTEGER1 is greater than INTEGER2

   INTEGER1 -le INTEGER2
          INTEGER1 is less than or equal to INTEGER2

   INTEGER1 -lt INTEGER2
          INTEGER1 is less than INTEGER2

   INTEGER1 -ne INTEGER2
          INTEGER1 is not equal to INTEGER2

operators == and != are for string comparison only.

for information: "[" command is an alias for system "test" command.