Created SC2034 (markdown)

SC2034.md

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+# foo appears unused. Verify it or export it.
+
+### Problematic code:
+
+    foo=42
+    echo "$FOO"
+
+### Correct code:
+
+    foo=42
+    echo "$foo"
+
+### Rationale:
+
+Variables not used for anything are often associated with bugs, so ShellCheck warns about them. 
+
+### Contraindications
+
+ShellCheck may not always realize that the variable is in use (especially with indirection), and may not realize you don't care (with throwaway variables or unimplemented features).
+
+For throwaway variables, consider using `_` as a dummy:
+
+    read _ last _ zip _ _ <<< "$str"
+    echo "$last, $zip"
+
+or use a directive to disable the warning:
+
+    # shellcheck disable=SC2034
+    read first last email zip lat lng <<< "$str"
+    echo "$last, $zip"
+
+For indirection, there's not much you can do without rewriting to use arrays or similar:
+
+    bar=42  # will always appear unused
+    foo=bar
+    echo "${!foo}" 
+
+This is expected behavior, and not a bug. There is no good way to statically analyze indirection in shell scripts, just like static C analyzers have a hard time preventing segfaults.
+
+As always, you can make an alias for `shellcheck -e SC2034` if you're frequently annoyed by this error.