Shellcheck

$ shellcheck test.sh

In test.sh line 6:
  if ["$a" -gt "$b"]
  ^-- SC1009: The mentioned syntax error was in this if expression.
     ^-- SC1035: You need a space after the [ and before the ].
     ^-- SC1073: Couldn't parse this test expression. Fix to allow more checks.
                    ^-- SC1020: You need a space before the ].
                    ^-- SC1072: Missing space before ]. Fix any mentioned problems and try again.