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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 BSD 4 38.Sh NAME 39.Nm sigvec 40.Nd software signal facilities 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.Fd #include <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 sigaction(2). 57.Ef 58.Pp 59The system defines a set of signals that may be delivered to a process. 60Signal delivery resembles the occurrence of a hardware interrupt: 61the signal is blocked from further occurrence, the current process 62context is saved, and a new one is built. A process may specify a 63.Em handler 64to which a signal is delivered, or specify that a signal is to be 65.Em blocked 66or 67.Em ignored . 68A process may also specify that a default action is to be taken 69by the system when a signal occurs. 70Normally, signal handlers execute on the current stack 71of the process. This may be changed, on a per-handler basis, 72so that signals are taken on a special 73.Em "signal stack" . 74.Pp 75All signals have the same 76.Em priority . 77Signal routines execute with the signal that caused their 78invocation 79.Em blocked , 80but other signals may yet occur. 81A global 82.Em "signal mask" 83defines the set of signals currently blocked from delivery 84to a process. The signal mask for a process is initialized 85from that of its parent (normally 0). It 86may be changed with a 87.Xr sigblock 2 88or 89.Xr sigsetmask 2 90call, or when a signal is delivered to the process. 91.Pp 92When a signal 93condition arises for a process, the signal is added to a set of 94signals pending for the process. If the signal is not currently 95.Em blocked 96by the process then it is delivered to the process. When a signal 97is delivered, the current state of the process is saved, 98a new signal mask is calculated (as described below), 99and the signal handler is invoked. The call to the handler 100is arranged so that if the signal handling routine returns 101normally the process will resume execution in the context 102from before the signal's delivery. 103If the process wishes to resume in a different context, then it 104must arrange to restore the previous context itself. 105.Pp 106When a signal is delivered to a process a new signal mask is 107installed for the duration of the process' signal handler 108(or until a 109.Xr sigblock 2 110or 111.Xr sigsetmask 2 112call is made). 113This mask is formed by taking the current signal mask, 114adding the signal to be delivered, and 115.Em or Ns 'ing 116in the signal mask associated with the handler to be invoked. 117.Pp 118.Fn Sigvec 119assigns a handler for a specific signal. If 120.Fa vec 121is non-zero, it 122specifies a handler routine and mask 123to be used when delivering the specified signal. 124Further, if the 125.Dv SV_ONSTACK 126bit is set in 127.Fa sv_flags , 128the system will deliver the signal to the process on a 129.Em "signal stack" , 130specified with 131.Xr sigaltstack 2 . 132If 133.Fa ovec 134is non-zero, the previous handling information for the signal 135is returned to the user. 136.Pp 137The following is a list of all signals 138with names as in the include file 139.Aq Pa signal.h : 140.Bl -column SIGVTALARMXX "create core imagexxx" 141.It Sy " NAME " " Default Action " " Description" 142.It Dv SIGHUP No " terminate process" " terminal line hangup" 143.It Dv SIGINT No " terminate process" " interrupt program" 144.It Dv SIGQUIT No " create core image" " quit program" 145.It Dv SIGILL No " create core image" " illegal instruction" 146.It Dv SIGTRAP No " create core image" " trace trap" 147.It Dv SIGABRT No " create core image" Xr abort 3 148call (formerly 149.Dv SIGIOT ) 150.It Dv SIGEMT No " create core image" " emulate instruction executed" 151.It Dv SIGFPE No " create core image" " floating-point exception" 152.It Dv SIGKILL No " terminate process" " kill program" 153.It Dv SIGBUS No " create core image" " bus error" 154.It Dv SIGSEGV No " create core image" " segmentation violation" 155.It Dv SIGSYS No " create core image" " non-existent system call invoked" 156.It Dv SIGPIPE No " terminate process" " write on a pipe with no reader" 157.It Dv SIGALRM No " terminate process" " real-time timer expired" 158.It Dv SIGTERM No " terminate process" " software termination signal" 159.It Dv SIGURG No " discard signal" " urgent condition present on socket" 160.It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)" 161.It Dv SIGTSTP No " stop process" " stop signal generated from keyboard" 162.It Dv SIGCONT No " discard signal" " continue after stop" 163.It Dv SIGCHLD No " discard signal" " child status has changed" 164.It Dv SIGTTIN No " stop process" " background read attempted from control terminal" 165.It Dv SIGTTOU No " stop process" " background write attempted to control terminal" 166.It Dv SIGIO No " discard signal" Tn " I/O" 167is possible on a descriptor (see 168.Xr fcntl 2 ) 169.It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see" 170.Xr setrlimit 2 ) 171.It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see" 172.Xr setrlimit 2 ) 173.It Dv SIGVTALRM No " terminate process" " virtual time alarm (see" 174.Xr setitimer 2 ) 175.It Dv SIGPROF No " terminate process" " profiling timer alarm (see" 176.Xr setitimer 2 ) 177.It Dv SIGWINCH No " discard signal" " Window size change" 178.It Dv SIGINFO No " discard signal" " status request from keyboard" 179.It Dv SIGUSR1 No " terminate process" " User defined signal 1" 180.It Dv SIGUSR2 No " terminate process" " User defined signal 2" 181.El 182.Pp 183Once a signal handler is installed, it remains installed 184until another 185.Fn sigvec 186call is made, or an 187.Xr execve 2 188is performed. 189A signal-specific default action may be reset by 190setting 191.Fa sv_handler 192to 193.Dv SIG_DFL . 194The defaults are process termination, possibly with core dump; 195no action; stopping the process; or continuing the process. 196See the above signal list for each signal's default action. 197If 198.Fa sv_handler 199is 200.Dv SIG_IGN 201current and pending instances 202of the signal are ignored and discarded. 203.Pp 204If a signal is caught during the system calls listed below, 205the call is normally restarted. 206The call can be forced to terminate prematurely with an 207.Dv EINTR 208error return by setting the 209.Dv SV_INTERRUPT 210bit in 211.Fa sv_flags . 212The affected system calls include 213.Xr read 2 , 214.Xr write 2 , 215.Xr sendto 2 , 216.Xr recvfrom 2 , 217.Xr sendmsg 2 218and 219.Xr recvmsg 2 220on a communications channel or a slow device (such as a terminal, 221but not a regular file) 222and during a 223.Xr wait 2 224or 225.Xr ioctl 2 . 226However, calls that have already committed are not restarted, 227but instead return a partial success (for example, a short read count). 228.Pp 229After a 230.Xr fork 2 231or 232.Xr vfork 2 233all signals, the signal mask, the signal stack, 234and the restart/interrupt flags are inherited by the child. 235.Pp 236.Xr Execve 2 237reinstates the default 238action for all signals which were caught and 239resets all signals to be caught on the user stack. 240Ignored signals remain ignored; 241the signal mask remains the same; 242signals that interrupt system calls continue to do so. 243.Sh NOTES 244The mask specified in 245.Fa vec 246is not allowed to block 247.Dv SIGKILL 248or 249.Dv SIGSTOP . 250This is done silently by the system. 251.Pp 252The 253.Dv SV_INTERRUPT 254flag is not available in 255.Bx 4.2 , 256hence it should not be used if backward compatibility is needed. 257.Sh RETURN VALUES 258A 0 value indicated that the call succeeded. A \-1 return value 259indicates an error occurred and 260.Va errno 261is set to indicated the reason. 262.Sh ERRORS 263.Fn Sigvec 264will fail and no new signal handler will be installed if one 265of the following occurs: 266.Bl -tag -width Er 267.It Bq Er EFAULT 268Either 269.Fa vec 270or 271.Fa ovec 272points to memory that is not a valid part of the process 273address space. 274.It Bq Er EINVAL 275.Fa Sig 276is not a valid signal number. 277.It Bq Er EINVAL 278An attempt is made to ignore or supply a handler for 279.Dv SIGKILL 280or 281.Dv SIGSTOP . 282.El 283.Sh SEE ALSO 284.Xr kill 1 , 285.Xr kill 2 , 286.Xr ptrace 2 , 287.Xr sigaction 2 , 288.Xr sigaltstack 2 , 289.Xr sigblock 2 , 290.Xr sigpause 2 , 291.Xr sigprocmask 2 , 292.Xr sigsetmask 2 , 293.Xr sigsuspend 2 , 294.Xr setjmp 3 , 295.Xr siginterrupt 3 , 296.Xr signal 3 , 297.Xr sigsetops 3 , 298.Xr tty 4 299.Sh EXAMPLE 300On the 301.Tn VAX\-11 302The handler routine can be declared: 303.Bd -literal -offset indent 304void handler(sig, code, scp) 305int sig, code; 306struct sigcontext *scp; 307.Ed 308.Pp 309Here 310.Fa sig 311is the signal number, into which the hardware faults and traps are 312mapped as defined below. 313.Fa Code 314is a parameter that is either a constant 315as given below or, for compatibility mode faults, the code provided by 316the hardware (Compatibility mode faults are distinguished from the 317other 318.Dv SIGILL 319traps by having 320.Dv PSL_CM 321set in the psl). 322.Fa Scp 323is a pointer to the 324.Fa sigcontext 325structure (defined in 326.Aq Pa signal.h ) , 327used to restore the context from before the signal. 328.Sh BUGS 329This manual page is still confusing. 330