Created SC3049 (markdown)

SC3049.md

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+## In POSIX sh, using lower/mixed case for signal names is undefined.
+
+### Problematic code:
+
+```sh
+trap 'handle_sigint' int
+```
+
+### Correct code:
+
+```sh
+trap 'handle_sigint' INT
+```
+
+### Rationale:
+
+POSIX requires that signal names [be given in uppercase](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_28):
+
+>The condition can be EXIT, 0 (equivalent to EXIT), or a signal specified using a symbolic name, without the SIG prefix, as listed in the tables of signal names in the <signal.h> header defined in XBD Headers; for example, HUP, INT, QUIT, TERM. Implementations may permit names with the SIG prefix or ignore case in signal names as an extension. 
+
+### Exceptions:
+
+None
+
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!