+++ /dev/null
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-.\"
-.\" @(#)signal.3 8.3 (Berkeley) 4/19/94
-.\" $FreeBSD: src/lib/libc/gen/signal.3,v 1.28 2001/10/01 16:08:51 ru Exp $
-.\"
-.Dd April 19, 1994
-.Dt SIGNAL 3
-.Os
-.Sh NAME
-.Nm signal
-.Nd simplified software signal facilities
-.Sh LIBRARY
-.Lb libc
-.Sh SYNOPSIS
-.In signal.h
-.\" The following is Quite Ugly, but syntactically correct. Don't try to
-.\" fix it.
-.Ft void \*(lp*
-.Fn signal "int sig" "void \*(lp*func\*(rp\*(lpint\*(rp\*(rp\*(rp\*(lpint"
-.Pp
-or in
-.Fx Ns 's
-equivalent but easier to read typedef'd version:
-.Ft typedef "void \*(lp*sig_t\*(rp \*(lpint\*(rp"
-.Ft sig_t
-.Fn signal "int sig" "sig_t func"
-.Sh DESCRIPTION
-This
-.Fn signal
-facility
-is a simplified interface to the more general
-.Xr sigaction 2
-facility.
-.Pp
-Signals allow the manipulation of a process from outside its
-domain as well as allowing the process to manipulate itself or
-copies of itself (children). There are two general types of signals:
-those that cause termination of a process and those that do not.
-Signals which cause termination of a program might result from
-an irrecoverable error or might be the result of a user at a terminal
-typing the `interrupt' character.
-Signals are used when a process is stopped because it wishes to access
-its control terminal while in the background (see
-.Xr tty 4 ) .
-Signals are optionally generated
-when a process resumes after being stopped,
-when the status of child processes changes,
-or when input is ready at the control terminal.
-Most signals result in the termination of the process receiving them
-if no action
-is taken; some signals instead cause the process receiving them
-to be stopped, or are simply discarded if the process has not
-requested otherwise.
-Except for the
-.Dv SIGKILL
-and
-.Dv SIGSTOP
-signals, the
-.Fn signal
-function allows for a signal to be caught, to be ignored, or to generate
-an interrupt.
-These signals are defined in the file
-.Aq Pa signal.h :
-.Bl -column SIGVTALARMXX "create core imagexxx"
-.It Sy "Name Default Action Description"
-.It Dv SIGHUP Ta "terminate process" Ta "terminal line hangup"
-.It Dv SIGINT Ta "terminate process" Ta "interrupt program"
-.It Dv SIGQUIT Ta "create core image" Ta "quit program"
-.It Dv SIGILL Ta "create core image" Ta "illegal instruction"
-.It Dv SIGTRAP Ta "create core image" Ta "trace trap"
-.It Dv SIGABRT Ta "create core image" Ta "abort program"
-(formerly
-.Dv SIGIOT )
-.It Dv SIGEMT Ta "create core image" Ta "emulate instruction executed"
-.It Dv SIGFPE Ta "create core image" Ta "floating-point exception"
-.It Dv SIGKILL Ta "terminate process" Ta "kill program"
-.It Dv SIGBUS Ta "create core image" Ta "bus error"
-.It Dv SIGSEGV Ta "create core image" Ta "segmentation violation"
-.It Dv SIGSYS Ta "create core image" Ta "non-existent system call invoked"
-.It Dv SIGPIPE Ta "terminate process" Ta "write on a pipe with no reader"
-.It Dv SIGALRM Ta "terminate process" Ta "real-time timer expired"
-.It Dv SIGTERM Ta "terminate process" Ta "software termination signal"
-.It Dv SIGURG Ta "discard signal" Ta "urgent condition present on socket"
-.It Dv SIGSTOP Ta "stop process" Ta "stop (cannot be caught or ignored)"
-.It Dv SIGTSTP Ta "stop process" Ta "stop signal generated from keyboard"
-.It Dv SIGCONT Ta "discard signal" Ta "continue after stop"
-.It Dv SIGCHLD Ta "discard signal" Ta "child status has changed"
-.It Dv SIGTTIN Ta "stop process" Ta "background read attempted from control terminal"
-.It Dv SIGTTOU Ta "stop process" Ta "background write attempted to control terminal"
-.It Dv SIGIO Ta "discard signal" Ta Tn "I/O"
-is possible on a descriptor (see
-.Xr fcntl 2 )
-.It Dv SIGXCPU Ta "terminate process" Ta "cpu time limit exceeded (see"
-.Xr setrlimit 2 )
-.It Dv SIGXFSZ Ta "terminate process" Ta "file size limit exceeded (see"
-.Xr setrlimit 2 )
-.It Dv SIGVTALRM Ta "terminate process" Ta "virtual time alarm (see"
-.Xr setitimer 2 )
-.It Dv SIGPROF Ta "terminate process" Ta "profiling timer alarm (see"
-.Xr setitimer 2 )
-.It Dv SIGWINCH Ta "discard signal" Ta "Window size change"
-.It Dv SIGINFO Ta "discard signal" Ta "status request from keyboard"
-.It Dv SIGUSR1 Ta "terminate process" Ta "User defined signal 1"
-.It Dv SIGUSR2 Ta "terminate process" Ta "User defined signal 2"
-.El
-.Pp
-The
-.Fa sig
-parameter specifies which signal was received.
-The
-.Fa func
-procedure allows a user to choose the action upon receipt of a signal.
-To set the default action of the signal to occur as listed above,
-.Fa func
-should be
-.Dv SIG_DFL .
-A
-.Dv SIG_DFL
-resets the default action.
-To ignore the signal
-.Fa func
-should be
-.Dv SIG_IGN .
-This will cause subsequent instances of the signal to be ignored
-and pending instances to be discarded.
-If
-.Dv SIG_IGN
-is not used,
-further occurrences of the signal are
-automatically blocked and
-.Fa func
-is called.
-.Pp
-The handled signal is unblocked when the
-function returns and
-the process continues from where it left off when the signal occurred.
-.Bf -symbolic
-Unlike previous signal facilities, the handler
-func() remains installed after a signal has been delivered.
-.Ef
-.Pp
-For some system calls, if a signal is caught while the call is
-executing and the call is prematurely terminated,
-the call is automatically restarted.
-(The handler is installed using the
-.Dv SA_RESTART
-flag with
-.Xr sigaction 2 . )
-The affected system calls include
-.Xr read 2 ,
-.Xr write 2 ,
-.Xr sendto 2 ,
-.Xr recvfrom 2 ,
-.Xr sendmsg 2
-and
-.Xr recvmsg 2
-on a communications channel or a low speed device
-and during a
-.Xr ioctl 2
-or
-.Xr wait 2 .
-However, calls that have already committed are not restarted,
-but instead return a partial success (for example, a short read count).
-This semantics could be changed with
-.Xr siginterrupt 3 .
-.Pp
-When a process which has installed signal handlers forks,
-the child process inherits the signals.
-All caught signals may be reset to their default action by a call
-to the
-.Xr execve 2
-function;
-ignored signals remain ignored.
-.Pp
-See
-.Xr sigaction 2
-for a list of functions
-that are considered safe for use in signal handler.
-.Sh RETURN VALUES
-The previous action is returned on a successful call.
-Otherwise, SIG_ERR is returned and the global variable
-.Va errno
-is set to indicate the error.
-.Sh ERRORS
-.Fn Signal
-will fail and no action will take place if one of the
-following occur:
-.Bl -tag -width Er
-.It Bq Er EINVAL
-.Em Sig
-is not a valid signal number.
-.It Bq Er EINVAL
-An attempt is made to ignore or supply a handler for
-.Dv SIGKILL
-or
-.Ev SIGSTOP .
-.El
-.Sh SEE ALSO
-.Xr kill 1 ,
-.Xr kill 2 ,
-.Xr ptrace 2 ,
-.Xr sigaction 2 ,
-.Xr sigaltstack 2 ,
-.Xr sigprocmask 2 ,
-.Xr sigsuspend 2 ,
-.Xr fpsetmask 3 ,
-.Xr setjmp 3 ,
-.Xr siginterrupt 3 ,
-.Xr tty 4
-.Sh HISTORY
-This
-.Fn signal
-facility appeared in
-.Bx 4.0 .
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