bsd_signal - Man Page

signal handling with BSD semantics


Standard C library (libc, -lc)


#include <signal.h>

typedef void (*sighandler_t)(int);

sighandler_t bsd_signal(int signum, sighandler_t handler);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):


    Since glibc 2.26:
        _XOPEN_SOURCE >= 500
            && ! (_POSIX_C_SOURCE >= 200809L)
    Glibc 2.25 and earlier:


The bsd_signal() function takes the same arguments, and performs the same task, as signal(2).

The difference between the two is that bsd_signal() is guaranteed to provide reliable signal semantics, that is: a) the disposition of the signal is not reset to the default when the handler is invoked; b) delivery of further instances of the signal is blocked while the signal handler is executing; and c) if the handler interrupts a blocking system call, then the system call is automatically restarted. A portable application cannot rely on signal(2) to provide these guarantees.

Return Value

The bsd_signal() function returns the previous value of the signal handler, or SIG_ERR on error.


As for signal(2).


For an explanation of the terms used in this section, see attributes(7).

bsd_signal()Thread safetyMT-Safe


4.2BSD, POSIX.1-2001. POSIX.1-2008 removes the specification of bsd_signal(), recommending the use of sigaction(2) instead.


Use of bsd_signal() should be avoided; use sigaction(2) instead.

On modern Linux systems, bsd_signal() and signal(2) are equivalent. But on older systems, signal(2) provided unreliable signal semantics; see signal(2) for details.

The use of sighandler_t is a GNU extension; this type is defined only if the _GNU_SOURCE feature test macro is defined.

See Also

sigaction(2), signal(2), sysv_signal(3), signal(7)

Referenced By

signal(2), signal(7), sysv_signal(3).

2022-12-15 Linux man-pages 6.02