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In POSIX sh, using lower/mixed case for signal names is undefined.

Problematic code:

trap 'handle_sigint' int

Correct code:

trap 'handle_sigint' INT

Rationale:

POSIX requires that signal names be given in uppercase:

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!

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