I think it's because - in Linux - signal
is implemented as a system call rather than a library function, and therefore belongs in Section 2 of the manual rather than Section 3.
You can add a Section 3 man page for the POSIX signal
implementation by installing the manpages-posix-dev
package:
$ dpkg -S $(man -w 3 signal)
manpages-posix-dev: /usr/share/man/man3/signal.3posix.gz
For compatibility reasons, glibc
also provides a signal
library function that is documented in Section 3 of the manpages as bsd_signal
:
BSD_SIGNAL(3) Linux Programmer's Manual BSD_SIGNAL(3)
NAME
bsd_signal - signal handling with BSD semantics
SYNOPSIS
#include <signal.h>
typedef void (*sighandler_t)(int);
sighandler_t bsd_signal(int signum, sighandler_t handler);
See also: