Why equal to operator does not work if it is not surrounded by space?

Question

I tried the following script

#!/bin/bash
var1=\"Test 1\" 
var2=\"Test 2\"
if [ \"$var1\"=\"$var2\" ] 
  then 
    echo \"Equal\" 
  else 
    echo \"Not equa         


        

Answer 1

When the shell reads

if [ "$var1" = "$var2" ]

it invokes the command [ with 4 arguments. Whether [ is a builtin or an external command is irrelevant, but it may help to understand that it may be the external command /bin/[. The second argument is the literal '=' and the fourth is ']'. However, when the shell reads

if [ "$var1"= "$var2" ]

[ only gets 3 arguments: the expansion of $var1 with '=' appended, the expansion of $var2, and ']'. When it gets only 3 arguments, it expects the last argument to be ']' and the first argument to be a unary operator.