Updated SC3012 (markdown)

SC3012.md

@@ -1,4 +1,4 @@
-## In POSIX sh, lexicographical \< is undefined.
+## In POSIX sh, lexicographical `\<` is undefined.
 
 ### Problematic code:
 
@@ -16,25 +16,23 @@ fi
 
 First, make sure you wanted a lexicographical comparison (aka dictionary order), and not a numerical comparison.
 
-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:
+Then to compare as string, you can use `expr` and make sure that the strings are not interpreted numerically by adding some non-numerical data to them. Here, an apostrophe is prepended:
 
 ```
 #!/bin/sh
 x="aardvark"
 y="zebra"
-if awk -v first="'$x'" -v second="'$y'" 'BEGIN { exit (first < second) ? 0 : 1 }'
+if expr "'$x" \< "'$y"   > /dev/null 
 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:
 
 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.
+The `expr` functionality is specified by POSIX.
 
 ### Exceptions:
 
@@ -42,4 +40,4 @@ If you know your `sh` will be e.g. `dash`, consider explicitly using `#!/bin/das
 
 ### Related resources:
 
-https://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html#tag_20_128
+* POSIX: [test](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html#tag_20_128), [expr](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/expr.html)