SYSV_SIGNAL(3)                                                          Linux Programmer's Manual                                                         SYSV_SIGNAL(3)

NAME
       sysv_signal - signal handling with System V semantics

SYNOPSIS
       #define _GNU_SOURCE         /* See feature_test_macros(7) */
       #include <signal.h>

       typedef void (*sighandler_t)(int);

       sighandler_t sysv_signal(int signum, sighandler_t handler);

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

       However  sysv_signal()  provides  the System V unreliable signal semantics, that is: a) the disposition of the signal is reset to the default when the handler is
       invoked; b) delivery of further instances of the signal is not blocked while the signal handler is executing; and c) if the handler interrupts (certain) blocking
       system calls, then the system call is not automatically restarted.

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

ERRORS
       As for signal(2).

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

       ┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                                                                                             │ Attribute     │ Value   │
       ├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │sysv_signal()                                                                                                                         │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO
       This function is nonstandard.

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

       On  older  Linux systems, sysv_signal() and signal(2) were equivalent.  But on newer systems, signal(2) provides reliable signal semantics; see signal(2) for de‐
       tails.

       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), bsd_signal(3), signal(7)

                                                                               2021-03-22                                                                 SYSV_SIGNAL(3)