Updated SC2170 (markdown)

SC2170.md

@@ -1,4 +1,4 @@
-## Numerical -eq does not dereference in [..]. Expand or use string operator.
+## Invalid number for -eq. Use = to compare as string (or use $var to expand as a variable).
 
 ### Problematic code:
 
@@ -8,16 +8,26 @@ if [ n -lt 0 ]
 then
    echo "bad input"
 fi
+
+if [ "$USER" -eq root ]
+then
+  echo "You are root"
+fi
 ```
 
 ### Correct code:
 
 ```sh
 read -r n
-if [ "$n" -lt 0 ]
+if [ "$n" -lt 0 ]        # Numerical comparison
 then
    echo "bad input"
 fi
+
+if [ "$USER" = root ]    # String comparison
+then
+  echo "You are root"
+fi
 ```
 ### Rationale:
 
@@ -27,7 +37,7 @@ In `[[ .. ]]`, this would automatically dereference the string, looking to see i
 
 In `[ .. ]`, which you are using, the string is just treated as an invalid number.
 
-If you want to compare numbers, expand yourself (e.g. use `$var` instead of `var`). If you are trying to compare strings and not numbers, use `=`, `!=` `\<` or `\>` instead.
+If you want to compare numbers, expand yourself (e.g. use `$var` instead of `var`, or `$((n+1))` instead of `n+1`). If you are trying to compare strings and not numbers, use `=`, `!=` `\<` or `\>` instead.
 
 ### Exceptions: