The integer signal number as defined by the operating system. Symbols such as SIGINT are defined to provide an operating-system independent method for specifying this number. (see signal)
block_signal causes a particular signal to be blocked until a call to unblock_signal is made. If the signal actually occurred while it was blocked, it will occur immediately when unblock_signal is called. Multiple occurrences of the signal while it was blocked will cause the signal to be reported multiple times when unblock_signal is called on most operating systems. Code that blocks signals should be surrounded by a call to unwind_protect.
Gamma> block_signal(14);
t
Gamma> kill(getpid(),14);
t
Gamma> unblock_signal(14);
Alarm clock
Gamma> block_signal (SIGINT);
t
Gamma> critical_function();
<function return>
Gamma> unblock_signal (SIGINT);
t
See the Linux or QNX section of the Abstracted Functions chapter of the Cogent Tools Demo and Tutorials book for an example of these functions used in context.