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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd April 2, 2022 29.Dt SIGVEC 2 30.Os 31.Sh NAME 32.Nm sigvec 33.Nd software signal facilities 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In signal.h 38.Bd -literal 39struct sigvec { 40 void (*sv_handler)(); 41 int sv_mask; 42 int sv_flags; 43}; 44.Ed 45.Ft int 46.Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec" 47.Sh DESCRIPTION 48.Bf -symbolic 49This interface is made obsolete by 50.Xr sigaction 2 . 51.Ef 52.Pp 53The system defines a set of signals that may be delivered to a process. 54Signal delivery resembles the occurrence of a hardware interrupt: 55the signal is blocked from further occurrence, the current process 56context is saved, and a new one is built. 57A process may specify a 58.Em handler 59to which a signal is delivered, or specify that a signal is to be 60.Em blocked 61or 62.Em ignored . 63A process may also specify that a default action is to be taken 64by the system when a signal occurs. 65Normally, signal handlers execute on the current stack 66of the process. 67This may be changed, on a per-handler basis, 68so that signals are taken on a special 69.Em "signal stack" . 70.Pp 71All signals have the same 72.Em priority . 73Signal routines execute with the signal that caused their 74invocation 75.Em blocked , 76but other signals may yet occur. 77A global 78.Em "signal mask" 79defines the set of signals currently blocked from delivery 80to a process. 81The signal mask for a process is initialized 82from that of its parent (normally 0). 83It 84may be changed with a 85.Xr sigblock 2 86or 87.Xr sigsetmask 2 88call, or when a signal is delivered to the process. 89.Pp 90When a signal 91condition arises for a process, the signal is added to a set of 92signals pending for the process. 93If the signal is not currently 94.Em blocked 95by the process then it is delivered to the process. 96When 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. 100The call to the handler 101is arranged so that if the signal handling routine returns 102normally the process will resume execution in the context 103from before the signal's delivery. 104If the process wishes to resume in a different context, then it 105must arrange to restore the previous context itself. 106.Pp 107When a signal is delivered to a process a new signal mask is 108installed for the duration of the process' signal handler 109(or until a 110.Xr sigblock 2 111or 112.Xr sigsetmask 2 113call is made). 114This mask is formed by taking the current signal mask, 115adding the signal to be delivered, and 116.Em or Ns 'ing 117in the signal mask associated with the handler to be invoked. 118.Pp 119The 120.Fn sigvec 121function 122assigns a handler for a specific signal. 123If 124.Fa vec 125is non-zero, it 126specifies a handler routine and mask 127to be used when delivering the specified signal. 128Further, if the 129.Dv SV_ONSTACK 130bit is set in 131.Fa sv_flags , 132the system will deliver the signal to the process on a 133.Em "signal stack" , 134specified with 135.Xr sigaltstack 2 . 136If 137.Fa ovec 138is non-zero, the previous handling information for the signal 139is returned to the user. 140.Pp 141The following is a list of all signals 142with names as in the include file 143.In signal.h : 144.Bl -column SIGVTALARMXX "create core imagexxx" 145.It Sy "NAME Default Action Description" 146.It Dv SIGHUP No " terminate process" " terminal line hangup" 147.It Dv SIGINT No " terminate process" " interrupt program" 148.It Dv SIGQUIT No " create core image" " quit program" 149.It Dv SIGILL No " create core image" " illegal instruction" 150.It Dv SIGTRAP No " create core image" " trace trap" 151.It Dv SIGABRT No " create core image" Ta Xr abort 3 152call (formerly 153.Dv SIGIOT ) 154.It Dv SIGEMT No " create core image" " emulate instruction executed" 155.It Dv SIGFPE No " create core image" " floating-point exception" 156.It Dv SIGKILL No " terminate process" " kill program" 157.It Dv SIGBUS No " create core image" " bus error" 158.It Dv SIGSEGV No " create core image" " segmentation violation" 159.It Dv SIGSYS No " create core image" " non-existent system call invoked" 160.It Dv SIGPIPE No " terminate process" " write on a pipe with no reader" 161.It Dv SIGALRM No " terminate process" " real-time timer expired" 162.It Dv SIGTERM No " terminate process" " software termination signal" 163.It Dv SIGURG No " discard signal" " urgent condition present on socket" 164.It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)" 165.It Dv SIGTSTP No " stop process" " stop signal generated from keyboard" 166.It Dv SIGCONT No " discard signal" " continue after stop" 167.It Dv SIGCHLD No " discard signal" " child status has changed" 168.It Dv SIGTTIN No " stop process" " background read attempted from control terminal" 169.It Dv SIGTTOU No " stop process" " background write attempted to control terminal" 170.It Dv SIGIO No " discard signal" Tn " I/O" 171is possible on a descriptor (see 172.Xr fcntl 2 ) 173.It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see" 174.Xr setrlimit 2 ) 175.It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see" 176.Xr setrlimit 2 ) 177.It Dv SIGVTALRM No " terminate process" " virtual time alarm (see" 178.Xr setitimer 2 ) 179.It Dv SIGPROF No " terminate process" " profiling timer alarm (see" 180.Xr setitimer 2 ) 181.It Dv SIGWINCH No " discard signal" " Window size change" 182.It Dv SIGINFO No " discard signal" " status request from keyboard" 183.It Dv SIGUSR1 No " terminate process" " User defined signal 1" 184.It Dv SIGUSR2 No " terminate process" " User defined signal 2" 185.El 186.Pp 187Once a signal handler is installed, it remains installed 188until another 189.Fn sigvec 190call is made, or an 191.Xr execve 2 192is performed. 193A signal-specific default action may be reset by 194setting 195.Fa sv_handler 196to 197.Dv SIG_DFL . 198The defaults are process termination, possibly with core dump; 199no action; stopping the process; or continuing the process. 200See the above signal list for each signal's default action. 201If 202.Fa sv_handler 203is 204.Dv SIG_IGN 205current and pending instances 206of the signal are ignored and discarded. 207.Pp 208If a signal is caught during the system calls listed below, 209the call is normally restarted. 210The call can be forced to terminate prematurely with an 211.Er EINTR 212error return by setting the 213.Dv SV_INTERRUPT 214bit in 215.Fa sv_flags . 216The affected system calls include 217.Xr read 2 , 218.Xr write 2 , 219.Xr sendto 2 , 220.Xr recvfrom 2 , 221.Xr sendmsg 2 222and 223.Xr recvmsg 2 224on a communications channel or a slow device (such as a terminal, 225but not a regular file) 226and during a 227.Xr wait 2 228or 229.Xr ioctl 2 . 230However, calls that have already committed are not restarted, 231but instead return a partial success (for example, a short read count). 232.Pp 233After a 234.Xr fork 2 235or 236.Xr vfork 2 237all signals, the signal mask, the signal stack, 238and the restart/interrupt flags are inherited by the child. 239.Pp 240The 241.Xr execve 2 242system call reinstates the default 243action for all signals which were caught and 244resets all signals to be caught on the user stack. 245Ignored signals remain ignored; 246the signal mask remains the same; 247signals that interrupt system calls continue to do so. 248.Sh NOTES 249The mask specified in 250.Fa vec 251is not allowed to block 252.Dv SIGKILL 253or 254.Dv SIGSTOP . 255This is done silently by the system. 256.Pp 257The 258.Dv SV_INTERRUPT 259flag is not available in 260.Bx 4.2 , 261hence it should not be used if backward compatibility is needed. 262.Sh RETURN VALUES 263.Rv -std sigvec 264.Sh EXAMPLES 265On the 266.Tn VAX\-11 267The handler routine can be declared: 268.Bd -literal -offset indent 269void handler(sig, code, scp) 270int sig, code; 271struct sigcontext *scp; 272.Ed 273.Pp 274Here 275.Fa sig 276is the signal number, into which the hardware faults and traps are 277mapped as defined below. 278The 279.Fa code 280argument 281is either a constant 282as given below or, for compatibility mode faults, the code provided by 283the hardware (Compatibility mode faults are distinguished from the 284other 285.Dv SIGILL 286traps by having 287.Dv PSL_CM 288set in the psl). 289The 290.Fa scp 291argument 292is a pointer to the 293.Fa sigcontext 294structure (defined in 295.In signal.h ) , 296used to restore the context from before the signal. 297.Sh ERRORS 298The 299.Fn sigvec 300function 301will fail and no new signal handler will be installed if one 302of the following occurs: 303.Bl -tag -width Er 304.It Bq Er EFAULT 305Either 306.Fa vec 307or 308.Fa ovec 309points to memory that is not a valid part of the process 310address space. 311.It Bq Er EINVAL 312The 313.Fa sig 314argument 315is not a valid signal number. 316.It Bq Er EINVAL 317An attempt is made to ignore or supply a handler for 318.Dv SIGKILL 319or 320.Dv SIGSTOP . 321.El 322.Sh SEE ALSO 323.Xr kill 1 , 324.Xr kill 2 , 325.Xr ptrace 2 , 326.Xr sigaction 2 , 327.Xr sigaltstack 2 , 328.Xr sigblock 2 , 329.Xr sigpause 2 , 330.Xr sigprocmask 2 , 331.Xr sigsetmask 2 , 332.Xr sigsuspend 2 , 333.Xr setjmp 3 , 334.Xr siginterrupt 3 , 335.Xr signal 3 , 336.Xr sigsetops 3 , 337.Xr tty 4 338.Sh HISTORY 339A 340.Fn sigvec 341system call first appeared in 342.Bx 4.2 . 343It was reimplemented as a wrapper around 344.Xr sigaction 2 345in 346.Bx 4.3 Reno . 347.Sh BUGS 348This manual page is still confusing. 349