Created SC2060 (markdown)

SC2060.md

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+# Quote parameters to tr to prevent glob expansion.
+
+### Problematic code:
+
+    tr -cd [:digit:]
+
+### Correct code:
+
+    tr -cd '[:digit:]'
+
+### Rationale:
+
+`[:digit:]` is a shell glob that matches any single character file named e.g. `g` or `t` in the current directory. Quoting it prevents the script from breaking in directories with files like this.
+
+### Contraindications
+
+None