245 lines
5.2 KiB
Groff
245 lines
5.2 KiB
Groff
|
.TH SIGACTION 2
|
||
|
|
.SH NAME
|
||
|
|
sigaction, signal \- manage signal state and handlers
|
||
|
|
.SH SYNOPSIS
|
||
|
|
.ft B
|
||
|
|
#include <signal.h>
|
||
|
|
|
||
|
|
.in +5
|
||
|
|
.ti -5
|
||
|
|
int sigaction(int \fIsig\fP, const struct sigaction *\fIact\fP, struct sigaction *\fIoact\fP)
|
||
|
|
.in -5
|
||
|
|
.br
|
||
|
|
void (*signal(int \fIsig\fP, void (*\fIhandler\fP)(int)))(int);
|
||
|
|
.ft P
|
||
|
|
.SH DESCRIPTION
|
||
|
|
.de SP
|
||
|
|
.if t .sp 0.4
|
||
|
|
.if n .sp
|
||
|
|
..
|
||
|
|
.B Sigaction()
|
||
|
|
is used to examine, set, or modify the attributes of a signal. The argument
|
||
|
|
.I sig
|
||
|
|
is the signal in question. The
|
||
|
|
.I act
|
||
|
|
argument points to a structure containing the new attributes of the signal,
|
||
|
|
the structure pointed to by
|
||
|
|
.I oact
|
||
|
|
will receive the old attributes that were in effect before the call.
|
||
|
|
.PP
|
||
|
|
The
|
||
|
|
.I act
|
||
|
|
and
|
||
|
|
.I oact
|
||
|
|
arguments may be
|
||
|
|
.B NULL
|
||
|
|
to indicate that either no new attributes are to be set, or that the old
|
||
|
|
attributes are not of interest.
|
||
|
|
.PP
|
||
|
|
The structure containing the signal attributes is defined in <signal.h> and
|
||
|
|
looks like this:
|
||
|
|
.PP
|
||
|
|
.RS
|
||
|
|
.nf
|
||
|
|
.ft B
|
||
|
|
.ta +4n +12n
|
||
|
|
struct sigaction {
|
||
|
|
void (*sa_handler)(int sig);
|
||
|
|
sigset_t sa_mask;
|
||
|
|
int sa_flags;
|
||
|
|
};
|
||
|
|
.ft R
|
||
|
|
.fi
|
||
|
|
.RE
|
||
|
|
.PP
|
||
|
|
The
|
||
|
|
.B sa_handler
|
||
|
|
field contains the address of a signal handler, a function that is called
|
||
|
|
when the process is signalled, or one of these special constants:
|
||
|
|
.PP
|
||
|
|
.TP 12
|
||
|
|
.B SIG_DFL
|
||
|
|
Default signal handling is to be performed. This usually means that the
|
||
|
|
process is killed, but some signals may be ignored by default.
|
||
|
|
.TP
|
||
|
|
.B SIG_IGN
|
||
|
|
Ignore the signal.
|
||
|
|
.PP
|
||
|
|
The
|
||
|
|
.B sa_mask
|
||
|
|
field indicates a set of signals that must be blocked when the signal is
|
||
|
|
being handled. Whether the signal
|
||
|
|
.I sig
|
||
|
|
itself is blocked when being handled is not controlled by this mask. The
|
||
|
|
mask is of a "signal set" type that is to be manipulated by the
|
||
|
|
.BR sigset (3)
|
||
|
|
functions.
|
||
|
|
.PP
|
||
|
|
How the signal is handled precisely is specified by bits in
|
||
|
|
.BR sa_flags .
|
||
|
|
If none of the flags is set then the handler is called when the signal
|
||
|
|
arrives. The signal is blocked during the call to the handler, and
|
||
|
|
unblocked when the handler returns. A system call that is interrupted
|
||
|
|
returns
|
||
|
|
.B \-1
|
||
|
|
with
|
||
|
|
.B errno
|
||
|
|
set to
|
||
|
|
.BR EINTR .
|
||
|
|
The following bit flags can be set to modify this behaviour:
|
||
|
|
.PP
|
||
|
|
.TP 15
|
||
|
|
.B SA_RESETHAND
|
||
|
|
Reset the signal handler to
|
||
|
|
.B SIG_DFL
|
||
|
|
when the signal is caught.
|
||
|
|
.TP
|
||
|
|
.B SA_NODEFER
|
||
|
|
Do not block the signal on entry to the handler.
|
||
|
|
.TP
|
||
|
|
.B SA_COMPAT
|
||
|
|
Handle the signal in a way that is compatible with the the old
|
||
|
|
.B signal()
|
||
|
|
call.
|
||
|
|
.PP
|
||
|
|
The old
|
||
|
|
.B signal()
|
||
|
|
signal system call sets a signal handler for a given signal and returns the
|
||
|
|
old signal handler. No signals are blocked, the flags are
|
||
|
|
.BR "SA_RESETHAND | SA_NODEFER | SA_COMPAT" .
|
||
|
|
New code should not use
|
||
|
|
.BR signal() .
|
||
|
|
Note that
|
||
|
|
.B signal()
|
||
|
|
and all of the
|
||
|
|
.B SA_*
|
||
|
|
flags are Minix extensions.
|
||
|
|
.PP
|
||
|
|
Signal handlers are reset to
|
||
|
|
.B SIG_DFL
|
||
|
|
on an
|
||
|
|
.BR execve (2).
|
||
|
|
Signals that are ignored stay ignored.
|
||
|
|
.SS Signals
|
||
|
|
Minix knows about the following signals:
|
||
|
|
.PP
|
||
|
|
.nf
|
||
|
|
.ta +11n +7n +8n
|
||
|
|
signal num notes description
|
||
|
|
.SP
|
||
|
|
SIGHUP 1 k Hangup
|
||
|
|
SIGINT 2 k Interrupt (usually DEL or CTRL\-C)
|
||
|
|
SIGQUIT 3 kc Quit (usually CTRL\-\e)
|
||
|
|
SIGILL 4 kc Illegal instruction
|
||
|
|
SIGTRAP 5 xkc Trace trap
|
||
|
|
SIGABRT 6 kc Abort program
|
||
|
|
SIGFPE 8 k Floating point exception
|
||
|
|
SIGKILL 9 k Kill
|
||
|
|
SIGUSR1 10 k User defined signal #1
|
||
|
|
SIGSEGV 11 kc Segmentation fault
|
||
|
|
SIGUSR2 12 k User defined signal #2
|
||
|
|
SIGPIPE 13 k Write to a pipe with no reader
|
||
|
|
SIGALRM 14 k Alarm clock
|
||
|
|
SIGTERM 15 k Terminate (default for kill(1))
|
||
|
|
SIGCHLD 17 pvi Child process terminated
|
||
|
|
SIGCONT 18 p Continue if stopped
|
||
|
|
SIGSTOP 19 ps Stop signal
|
||
|
|
SIGTSTP 20 ps Interactive stop signal
|
||
|
|
SIGTTIN 21 ps Background read
|
||
|
|
SIGTTOU 22 ps Background write
|
||
|
|
SIGWINCH 23 xvi Window size change
|
||
|
|
.ft R
|
||
|
|
.fi
|
||
|
|
.PP
|
||
|
|
The letters in the notes column indicate:
|
||
|
|
.PP
|
||
|
|
.TP 5
|
||
|
|
.B k
|
||
|
|
The process is killed if the signal is not caught.
|
||
|
|
.TP
|
||
|
|
.B c
|
||
|
|
The signal causes a core dump.
|
||
|
|
.TP
|
||
|
|
.B i
|
||
|
|
The signal is ignored if not caught.
|
||
|
|
.TP
|
||
|
|
.B v
|
||
|
|
Only Minix-vmd implements this signal.
|
||
|
|
.TP
|
||
|
|
.B x
|
||
|
|
Minix extension, not defined by \s-2POSIX\s+2.
|
||
|
|
.TP
|
||
|
|
.B p
|
||
|
|
These signals are not implemented, but \s-2POSIX\s+2 requires that they are
|
||
|
|
defined.
|
||
|
|
.TP
|
||
|
|
.B s
|
||
|
|
The process should be stopped, but is killed instead.
|
||
|
|
.PP
|
||
|
|
The
|
||
|
|
.B SIGKILL
|
||
|
|
signal cannot be caught or ignored. The
|
||
|
|
.B SIGILL
|
||
|
|
and
|
||
|
|
.B SIGTRAP
|
||
|
|
signals cannot be automatically reset. The system silently enforces these
|
||
|
|
restrictions. This may or may not be reflected by the attributes of these
|
||
|
|
signals and the signal masks.
|
||
|
|
.SS Types
|
||
|
|
\s-2POSIX\s+2 prescribes that <sys/types.h> has the following definition:
|
||
|
|
.PP
|
||
|
|
.RS
|
||
|
|
.B "typedef int (*sighandler_t)(int)"
|
||
|
|
.RE
|
||
|
|
.PP
|
||
|
|
With this type the following declarations can be made:
|
||
|
|
.PP
|
||
|
|
.RS
|
||
|
|
.ft B
|
||
|
|
.nf
|
||
|
|
sighandler_t sa_handler;
|
||
|
|
sighandler_t signal(int \fIsig\fP, sighandler_t \fIhandler\fP);
|
||
|
|
.fi
|
||
|
|
.ft R
|
||
|
|
.RE
|
||
|
|
.PP
|
||
|
|
This may help you to understand the earlier declarations better. The
|
||
|
|
.B sighandler_t
|
||
|
|
type is also very useful in old style C code that is compiled by a compiler
|
||
|
|
for standard C.
|
||
|
|
.SH "SEE ALSO"
|
||
|
|
.BR kill (1),
|
||
|
|
.BR kill (2),
|
||
|
|
.BR pause (2),
|
||
|
|
.BR sigprocmask (2),
|
||
|
|
.BR sigsuspend (2),
|
||
|
|
.BR sigpending (2),
|
||
|
|
.BR sigset (3).
|
||
|
|
.SH DIAGNOSTICS
|
||
|
|
.B Sigaction()
|
||
|
|
returns
|
||
|
|
.B 0
|
||
|
|
on success or
|
||
|
|
.B \-1
|
||
|
|
on error.
|
||
|
|
.B Signal()
|
||
|
|
returns the old handler on success or
|
||
|
|
.B SIG_ERR
|
||
|
|
on error. The error code may be:
|
||
|
|
.PP
|
||
|
|
.TP 10
|
||
|
|
.B EINVAL
|
||
|
|
Bad signal number.
|
||
|
|
.TP
|
||
|
|
.B EFAULT
|
||
|
|
Bad
|
||
|
|
.I act
|
||
|
|
or
|
||
|
|
.I oact
|
||
|
|
addresses.
|
||
|
|
.SH AUTHOR
|
||
|
|
Kees J. Bot (kjb@cs.vu.nl)
|
||
|
|
|
||
|
|
.\"
|
||
|
|
.\" $PchId: sigaction.2,v 1.2 1996/04/11 06:00:28 philip Exp $
|