1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sigvec.2 8.2 (Berkeley) 4/19/94 33.\" $FreeBSD$ 34.\" 35.Dd April 19, 1994 36.Dt SIGVEC 2 37.Os 38.Sh NAME 39.Nm sigvec 40.Nd software signal facilities 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In signal.h 45.Bd -literal 46struct sigvec { 47 void (*sv_handler)(); 48 int sv_mask; 49 int sv_flags; 50}; 51.Ed 52.Ft int 53.Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec" 54.Sh DESCRIPTION 55.Bf -symbolic 56This interface is made obsolete by 57.Xr sigaction 2 . 58.Ef 59.Pp 60The system defines a set of signals that may be delivered to a process. 61Signal delivery resembles the occurrence of a hardware interrupt: 62the signal is blocked from further occurrence, the current process 63context is saved, and a new one is built. 64A process may specify a 65.Em handler 66to which a signal is delivered, or specify that a signal is to be 67.Em blocked 68or 69.Em ignored . 70A process may also specify that a default action is to be taken 71by the system when a signal occurs. 72Normally, signal handlers execute on the current stack 73of the process. 74This may be changed, on a per-handler basis, 75so that signals are taken on a special 76.Em "signal stack" . 77.Pp 78All signals have the same 79.Em priority . 80Signal routines execute with the signal that caused their 81invocation 82.Em blocked , 83but other signals may yet occur. 84A global 85.Em "signal mask" 86defines the set of signals currently blocked from delivery 87to a process. 88The signal mask for a process is initialized 89from that of its parent (normally 0). 90It 91may be changed with a 92.Xr sigblock 2 93or 94.Xr sigsetmask 2 95call, or when a signal is delivered to the process. 96.Pp 97When a signal 98condition arises for a process, the signal is added to a set of 99signals pending for the process. 100If the signal is not currently 101.Em blocked 102by the process then it is delivered to the process. 103When a signal 104is delivered, the current state of the process is saved, 105a new signal mask is calculated (as described below), 106and the signal handler is invoked. 107The call to the handler 108is arranged so that if the signal handling routine returns 109normally the process will resume execution in the context 110from before the signal's delivery. 111If the process wishes to resume in a different context, then it 112must arrange to restore the previous context itself. 113.Pp 114When a signal is delivered to a process a new signal mask is 115installed for the duration of the process' signal handler 116(or until a 117.Xr sigblock 2 118or 119.Xr sigsetmask 2 120call is made). 121This mask is formed by taking the current signal mask, 122adding the signal to be delivered, and 123.Em or Ns 'ing 124in the signal mask associated with the handler to be invoked. 125.Pp 126The 127.Fn sigvec 128function 129assigns a handler for a specific signal. 130If 131.Fa vec 132is non-zero, it 133specifies a handler routine and mask 134to be used when delivering the specified signal. 135Further, if the 136.Dv SV_ONSTACK 137bit is set in 138.Fa sv_flags , 139the system will deliver the signal to the process on a 140.Em "signal stack" , 141specified with 142.Xr sigaltstack 2 . 143If 144.Fa ovec 145is non-zero, the previous handling information for the signal 146is returned to the user. 147.Pp 148The following is a list of all signals 149with names as in the include file 150.In signal.h : 151.Bl -column SIGVTALARMXX "create core imagexxx" 152.It Sy "NAME Default Action Description" 153.It Dv SIGHUP No " terminate process" " terminal line hangup" 154.It Dv SIGINT No " terminate process" " interrupt program" 155.It Dv SIGQUIT No " create core image" " quit program" 156.It Dv SIGILL No " create core image" " illegal instruction" 157.It Dv SIGTRAP No " create core image" " trace trap" 158.It Dv SIGABRT No " create core image" Ta Xr abort 3 159call (formerly 160.Dv SIGIOT ) 161.It Dv SIGEMT No " create core image" " emulate instruction executed" 162.It Dv SIGFPE No " create core image" " floating-point exception" 163.It Dv SIGKILL No " terminate process" " kill program" 164.It Dv SIGBUS No " create core image" " bus error" 165.It Dv SIGSEGV No " create core image" " segmentation violation" 166.It Dv SIGSYS No " create core image" " non-existent system call invoked" 167.It Dv SIGPIPE No " terminate process" " write on a pipe with no reader" 168.It Dv SIGALRM No " terminate process" " real-time timer expired" 169.It Dv SIGTERM No " terminate process" " software termination signal" 170.It Dv SIGURG No " discard signal" " urgent condition present on socket" 171.It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)" 172.It Dv SIGTSTP No " stop process" " stop signal generated from keyboard" 173.It Dv SIGCONT No " discard signal" " continue after stop" 174.It Dv SIGCHLD No " discard signal" " child status has changed" 175.It Dv SIGTTIN No " stop process" " background read attempted from control terminal" 176.It Dv SIGTTOU No " stop process" " background write attempted to control terminal" 177.It Dv SIGIO No " discard signal" Tn " I/O" 178is possible on a descriptor (see 179.Xr fcntl 2 ) 180.It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see" 181.Xr setrlimit 2 ) 182.It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see" 183.Xr setrlimit 2 ) 184.It Dv SIGVTALRM No " terminate process" " virtual time alarm (see" 185.Xr setitimer 2 ) 186.It Dv SIGPROF No " terminate process" " profiling timer alarm (see" 187.Xr setitimer 2 ) 188.It Dv SIGWINCH No " discard signal" " Window size change" 189.It Dv SIGINFO No " discard signal" " status request from keyboard" 190.It Dv SIGUSR1 No " terminate process" " User defined signal 1" 191.It Dv SIGUSR2 No " terminate process" " User defined signal 2" 192.El 193.Pp 194Once a signal handler is installed, it remains installed 195until another 196.Fn sigvec 197call is made, or an 198.Xr execve 2 199is performed. 200A signal-specific default action may be reset by 201setting 202.Fa sv_handler 203to 204.Dv SIG_DFL . 205The defaults are process termination, possibly with core dump; 206no action; stopping the process; or continuing the process. 207See the above signal list for each signal's default action. 208If 209.Fa sv_handler 210is 211.Dv SIG_IGN 212current and pending instances 213of the signal are ignored and discarded. 214.Pp 215If a signal is caught during the system calls listed below, 216the call is normally restarted. 217The call can be forced to terminate prematurely with an 218.Er EINTR 219error return by setting the 220.Dv SV_INTERRUPT 221bit in 222.Fa sv_flags . 223The affected system calls include 224.Xr read 2 , 225.Xr write 2 , 226.Xr sendto 2 , 227.Xr recvfrom 2 , 228.Xr sendmsg 2 229and 230.Xr recvmsg 2 231on a communications channel or a slow device (such as a terminal, 232but not a regular file) 233and during a 234.Xr wait 2 235or 236.Xr ioctl 2 . 237However, calls that have already committed are not restarted, 238but instead return a partial success (for example, a short read count). 239.Pp 240After a 241.Xr fork 2 242or 243.Xr vfork 2 244all signals, the signal mask, the signal stack, 245and the restart/interrupt flags are inherited by the child. 246.Pp 247The 248.Xr execve 2 249system call reinstates the default 250action for all signals which were caught and 251resets all signals to be caught on the user stack. 252Ignored signals remain ignored; 253the signal mask remains the same; 254signals that interrupt system calls continue to do so. 255.Sh NOTES 256The mask specified in 257.Fa vec 258is not allowed to block 259.Dv SIGKILL 260or 261.Dv SIGSTOP . 262This is done silently by the system. 263.Pp 264The 265.Dv SV_INTERRUPT 266flag is not available in 267.Bx 4.2 , 268hence it should not be used if backward compatibility is needed. 269.Sh RETURN VALUES 270.Rv -std sigvec 271.Sh ERRORS 272The 273.Fn sigvec 274function 275will fail and no new signal handler will be installed if one 276of the following occurs: 277.Bl -tag -width Er 278.It Bq Er EFAULT 279Either 280.Fa vec 281or 282.Fa ovec 283points to memory that is not a valid part of the process 284address space. 285.It Bq Er EINVAL 286The 287.Fa sig 288argument 289is not a valid signal number. 290.It Bq Er EINVAL 291An attempt is made to ignore or supply a handler for 292.Dv SIGKILL 293or 294.Dv SIGSTOP . 295.El 296.Sh SEE ALSO 297.Xr kill 1 , 298.Xr kill 2 , 299.Xr ptrace 2 , 300.Xr sigaction 2 , 301.Xr sigaltstack 2 , 302.Xr sigblock 2 , 303.Xr sigpause 2 , 304.Xr sigprocmask 2 , 305.Xr sigsetmask 2 , 306.Xr sigsuspend 2 , 307.Xr setjmp 3 , 308.Xr siginterrupt 3 , 309.Xr signal 3 , 310.Xr sigsetops 3 , 311.Xr tty 4 312.Sh EXAMPLES 313On the 314.Tn VAX\-11 315The handler routine can be declared: 316.Bd -literal -offset indent 317void handler(sig, code, scp) 318int sig, code; 319struct sigcontext *scp; 320.Ed 321.Pp 322Here 323.Fa sig 324is the signal number, into which the hardware faults and traps are 325mapped as defined below. 326The 327.Fa code 328argument 329is either a constant 330as given below or, for compatibility mode faults, the code provided by 331the hardware (Compatibility mode faults are distinguished from the 332other 333.Dv SIGILL 334traps by having 335.Dv PSL_CM 336set in the psl). 337The 338.Fa scp 339argument 340is a pointer to the 341.Fa sigcontext 342structure (defined in 343.In signal.h ) , 344used to restore the context from before the signal. 345.Sh BUGS 346This manual page is still confusing. 347