get pending signals
Standard C Library (libc, -lc)
sigpending() system call returns a mask of the
signals pending for delivery to the calling thread or the calling process in
the location indicated by set. Signals may be pending
because they are currently masked, or transiently before delivery (although
the latter case is not normally detectable).
sigpending() function returns the value 0 if
successful; otherwise the value -1 is returned and the global variable
errno is set to indicate the error.
sigpending() system call will fail if:
- The set argument specified an invalid address.
sigpending() system call is expected to conform to
IEEE Std 1003.1-1990 (“POSIX.1”).