Updated SC3053 (markdown)

SC3053.md

@@ -1,36 +1,36 @@
-## In POSIX sh, array references are undefined.
+## In POSIX sh, indirect expansion is undefined.
 
-(or "In dash, ... are not supported." when using `dash`)
+(or "In dash, ... is not supported." when using `dash`)
 
 ### Problematic code:
 
 ```sh
 #!/bin/sh
-var=(foo bar)
-echo "${var[1]}"
+name="PATH"
+echo "${!name}"
 ```
 
 ### Correct code:
 
-The easiest solution is to switch to a shell that does support arrays, like `bash`:
+The easiest solution is to switch to a shell that does support indirect expansion, like `bash`:
 
 ```sh
 #!/bin/bash
-var=(foo bar)
-echo "${var[1]}"
+name="PATH"
+echo "${!name}"
 ```
 
-Alternatively, rewrite the logic to use e.g. indirect variable references or `set`:
+Alternatively, carefully rewrite using `eval`:
 
 ```sh
 #!/bin/sh
-set -- foo bar
-echo "$2"
+name=PATH
+eval "echo \"\$$name\""
 ```
 
 ### Rationale:
 
-Arrays are supported in `bash` and `ksh`, but not in `dash` or POSIX `sh`. Either switch to a shell that supports them, or rewrite your script without relying on arrays. This may not be straight forward.
+Indirection expansion is an extension in `bash` and `ksh`, and not supported in `dash` or POSIX `sh`. Either switch to a shell that supports them, or write around it with careful use of `eval`. Take care to validate the variable name to avoid fragility and code injection.
 
 ### Exceptions: