Created SC2253 (markdown)

SC2253.md

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+## Use -R to recurse, or explicitly a-r to remove read permissions.
+
+### Problematic code:
+
+```sh
+chmod -r 0700 dir
+chmod -r file
+```
+
+### Correct code:
+
+```sh
+chmod -R 0700 dir
+chmod a-r file
+```
+
+### Rationale:
+
+Many tools use `-r` for recursive operation, but in `chmod` this removes read permissions.
+
+If you wanted to change permissions recursively, change the flag to `-R`. If you wanted to remove read permissions, consider using `a-r` explicitly to make this more obvious.
+
+### Exceptions:
+
+If you're using it correctly and don't mind the potential for confusion, you can save a single character by ignoring this warning.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!