Updated SC3012 (markdown)

SC3012.md

@@ -1,27 +1,44 @@
-## In POSIX sh, lexicographical \> is undefined.
+## In POSIX sh, lexicographical \< is undefined.
 
 ### Problematic code:
 
 ```sh
 #!/bin/sh
-x=1.31
+x="aardvark"
-y=1.29
+y="zebra"
-! [ $x \> $y ]
+if [ $x \< $y ]
+then
+  echo "$x comes before $y in the dictionary"
+fi
 ```
 
 ### Correct code:
 
-The easiest fix is to switch to a shell that *does* support lexicographical \>.
+First, make sure you wanted a lexicographical comparison (aka dictionary order), and not a numerical comparison.
 
-Please add common code examples.
+The easiest fix is to switch to a shell that *does* support lexicographical comparison with `>`/`\>`, such as `bash`, `dash`, or `ksh`. Otherwise, you can use `awk` to compare lexicographically by making sure the strings contain at least some non-numerical data:
+
+```
+#!/bin/sh
+x="aardvark"
+y="zebra"
+if awk -v first="'$x'" -v second="'$y'" 'BEGIN { exit (first < second) ? 0 : 1 }'
+then
+  echo "$x comes before $y in the dictionary"
+fi
+```
+
+The extra quotes in the awk `-v` flag are there to add non-numerical data to the string, otherwise `10 < 2` is treated as a numerical comparison (being false) instead of a lexicographical string comparison (being true). Any other non-numerical data can be used instead, such as `-v x="FOO$x"`.
 
 ### Rationale:
 
-Please expand on this section.
+The `test` binary operators `>`, `\>`, `<`, and `\<` are not part of POSIX and not guaranteed to be supported in scripts targeting `sh`.
+
+The `awk` functionality is POSIX and can safely be relied on.
 
 ### Exceptions:
 
-Please expand on this section.
+If you know your `sh` will be e.g. `dash`, consider explicitly using `#!/bin/dash`. 
 
 ### Related resources: