Created SC3062 (markdown)

SC3062.md

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+## In POSIX sh, unary -o to check options is undefined.
+
+### Problematic code:
+
+```sh
+if [ -o braceexpand ]
+then
+ echo "Brace expansion available and enabled."
+fi
+```
+
+### Correct code:
+
+`$-` will be set to a list of shell options:
+
+```sh
+case $- of
+  *B*) echo "Brace expansion available and enabled."
+esac 
+```
+
+However, not all options are available through `$-`. If you need to check those, ignore this suggestion with a directive:
+
+```sh
+# shellcheck disable=SC3062
+if [ -n "$BASH_VERSION" ] && [ -o pipefail ]
+then
+  echo "This is bash and pipefail is enabled."
+fi
+```
+
+### Rationale:
+
+`[ -o option ]` is a bash/ksh extension, while `$-` is standard POSIX. Do note that letters outside the POSIX set are not guaranteed to be compatible, such as `B` above.
+
+### Exceptions:
+
+As described.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!