{ "mode": "man", "parameter": "signal", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/signal/7/json", "generated": "2026-06-02T15:55:32Z", "sections": { "NAME": { "content": "signal - overview of signals\n", "subsections": [] }, "DESCRIPTION": { "content": "Linux supports both POSIX reliable signals (hereinafter \"standard signals\") and POSIX real-\ntime signals.\n", "subsections": [ { "name": "Signal dispositions", "content": "Each signal has a current disposition, which determines how the process behaves when it is\ndelivered the signal.\n\nThe entries in the \"Action\" column of the table below specify the default disposition for\neach signal, as follows:\n\nTerm Default action is to terminate the process.\n\nIgn Default action is to ignore the signal.\n\nCore Default action is to terminate the process and dump core (see core(5)).\n\nStop Default action is to stop the process.\n\nCont Default action is to continue the process if it is currently stopped.\n\nA process can change the disposition of a signal using sigaction(2) or signal(2). (The lat‐\nter is less portable when establishing a signal handler; see signal(2) for details.) Using\nthese system calls, a process can elect one of the following behaviors to occur on delivery\nof the signal: perform the default action; ignore the signal; or catch the signal with a sig‐\nnal handler, a programmer-defined function that is automatically invoked when the signal is\ndelivered.\n\nBy default, a signal handler is invoked on the normal process stack. It is possible to ar‐\nrange that the signal handler uses an alternate stack; see sigaltstack(2) for a discussion of\nhow to do this and when it might be useful.\n\nThe signal disposition is a per-process attribute: in a multithreaded application, the dispo‐\nsition of a particular signal is the same for all threads.\n\nA child created via fork(2) inherits a copy of its parent's signal dispositions. During an\nexecve(2), the dispositions of handled signals are reset to the default; the dispositions of\nignored signals are left unchanged.\n" }, { "name": "Sending a signal", "content": "The following system calls and library functions allow the caller to send a signal:\n\nraise(3)\nSends a signal to the calling thread.\n\nkill(2)\nSends a signal to a specified process, to all members of a specified process group, or\nto all processes on the system.\n\npidfdsendsignal(2)\nSends a signal to a process identified by a PID file descriptor.\n\nkillpg(3)\nSends a signal to all of the members of a specified process group.\n\npthreadkill(3)\nSends a signal to a specified POSIX thread in the same process as the caller.\n\ntgkill(2)\nSends a signal to a specified thread within a specific process. (This is the system\ncall used to implement pthreadkill(3).)\n\nsigqueue(3)\nSends a real-time signal with accompanying data to a specified process.\n" }, { "name": "Waiting for a signal to be caught", "content": "The following system calls suspend execution of the calling thread until a signal is caught\n(or an unhandled signal terminates the process):\n\npause(2)\nSuspends execution until any signal is caught.\n\nsigsuspend(2)\nTemporarily changes the signal mask (see below) and suspends execution until one of\nthe unmasked signals is caught.\n" }, { "name": "Synchronously accepting a signal", "content": "Rather than asynchronously catching a signal via a signal handler, it is possible to syn‐\nchronously accept the signal, that is, to block execution until the signal is delivered, at\nwhich point the kernel returns information about the signal to the caller. There are two\ngeneral ways to do this:\n\n* sigwaitinfo(2), sigtimedwait(2), and sigwait(3) suspend execution until one of the signals\nin a specified set is delivered. Each of these calls returns information about the deliv‐\nered signal.\n\n* signalfd(2) returns a file descriptor that can be used to read information about signals\nthat are delivered to the caller. Each read(2) from this file descriptor blocks until one\nof the signals in the set specified in the signalfd(2) call is delivered to the caller.\nThe buffer returned by read(2) contains a structure describing the signal.\n" }, { "name": "Signal mask and pending signals", "content": "A signal may be blocked, which means that it will not be delivered until it is later un‐\nblocked. Between the time when it is generated and when it is delivered a signal is said to\nbe pending.\n\nEach thread in a process has an independent signal mask, which indicates the set of signals\nthat the thread is currently blocking. A thread can manipulate its signal mask using\npthreadsigmask(3). In a traditional single-threaded application, sigprocmask(2) can be used\nto manipulate the signal mask.\n\nA child created via fork(2) inherits a copy of its parent's signal mask; the signal mask is\npreserved across execve(2).\n\nA signal may be process-directed or thread-directed. A process-directed signal is one that\nis targeted at (and thus pending for) the process as a whole. A signal may be process-di‐\nrected because it was generated by the kernel for reasons other than a hardware exception, or\nbecause it was sent using kill(2) or sigqueue(3). A thread-directed signal is one that is\ntargeted at a specific thread. A signal may be thread-directed because it was generated as a\nconsequence of executing a specific machine-language instruction that triggered a hardware\nexception (e.g., SIGSEGV for an invalid memory access, or SIGFPE for a math error), or be‐\ncause it was targeted at a specific thread using interfaces such as tgkill(2) or\npthreadkill(3).\n\nA process-directed signal may be delivered to any one of the threads that does not currently\nhave the signal blocked. If more than one of the threads has the signal unblocked, then the\nkernel chooses an arbitrary thread to which to deliver the signal.\n\nA thread can obtain the set of signals that it currently has pending using sigpending(2).\nThis set will consist of the union of the set of pending process-directed signals and the set\nof signals pending for the calling thread.\n\nA child created via fork(2) initially has an empty pending signal set; the pending signal set\nis preserved across an execve(2).\n" }, { "name": "Execution of signal handlers", "content": "Whenever there is a transition from kernel-mode to user-mode execution (e.g., on return from\na system call or scheduling of a thread onto the CPU), the kernel checks whether there is a\npending unblocked signal for which the process has established a signal handler. If there is\nsuch a pending signal, the following steps occur:\n\n1. The kernel performs the necessary preparatory steps for execution of the signal handler:\n\na) The signal is removed from the set of pending signals.\n\nb) If the signal handler was installed by a call to sigaction(2) that specified the SAON‐‐\nSTACK flag and the thread has defined an alternate signal stack (using sigaltstack(2)),\nthen that stack is installed.\n\nc) Various pieces of signal-related context are saved into a special frame that is created\non the stack. The saved information includes:\n\n+ the program counter register (i.e., the address of the next instruction in the main\nprogram that should be executed when the signal handler returns);\n\n+ architecture-specific register state required for resuming the interrupted program;\n\n+ the thread's current signal mask;\n\n+ the thread's alternate signal stack settings.\n\n(If the signal handler was installed using the sigaction(2) SASIGINFO flag, then the\nabove information is accessible via the ucontextt object that is pointed to by the\nthird argument of the signal handler.)\n\nd) Any signals specified in act->samask when registering the handler with sigprocmask(2)\nare added to the thread's signal mask. The signal being delivered is also added to the\nsignal mask, unless SANODEFER was specified when registering the handler. These sig‐\nnals are thus blocked while the handler executes.\n\n2. The kernel constructs a frame for the signal handler on the stack. The kernel sets the\nprogram counter for the thread to point to the first instruction of the signal handler\nfunction, and configures the return address for that function to point to a piece of user-\nspace code known as the signal trampoline (described in sigreturn(2)).\n\n3. The kernel passes control back to user-space, where execution commences at the start of\nthe signal handler function.\n\n4. When the signal handler returns, control passes to the signal trampoline code.\n\n5. The signal trampoline calls sigreturn(2), a system call that uses the information in the\nstack frame created in step 1 to restore the thread to its state before the signal handler\nwas called. The thread's signal mask and alternate signal stack settings are restored as\npart of this procedure. Upon completion of the call to sigreturn(2), the kernel transfers\ncontrol back to user space, and the thread recommences execution at the point where it was\ninterrupted by the signal handler.\n\nNote that if the signal handler does not return (e.g., control is transferred out of the han‐\ndler using siglongjmp(3), or the handler executes a new program with execve(2)), then the fi‐\nnal step is not performed. In particular, in such scenarios it is the programmer's responsi‐\nbility to restore the state of the signal mask (using sigprocmask(2)), if it is desired to\nunblock the signals that were blocked on entry to the signal handler. (Note that sig‐‐\nlongjmp(3) may or may not restore the signal mask, depending on the savesigs value that was\nspecified in the corresponding call to sigsetjmp(3).)\n\nFrom the kernel's point of view, execution of the signal handler code is exactly the same as\nthe execution of any other user-space code. That is to say, the kernel does not record any\nspecial state information indicating that the thread is currently excuting inside a signal\nhandler. All necessary state information is maintained in user-space registers and the user-\nspace stack. The depth to which nested signal handlers may be invoked is thus limited only\nby the user-space stack (and sensible software design!).\n" }, { "name": "Standard signals", "content": "Linux supports the standard signals listed below. The second column of the table indicates\nwhich standard (if any) specified the signal: \"P1990\" indicates that the signal is described\nin the original POSIX.1-1990 standard; \"P2001\" indicates that the signal was added in SUSv2\nand POSIX.1-2001.\n\nSignal Standard Action Comment\n────────────────────────────────────────────────────────────────────────\nSIGABRT P1990 Core Abort signal from abort(3)\nSIGALRM P1990 Term Timer signal from alarm(2)\nSIGBUS P2001 Core Bus error (bad memory access)\nSIGCHLD P1990 Ign Child stopped or terminated\nSIGCLD - Ign A synonym for SIGCHLD\nSIGCONT P1990 Cont Continue if stopped\nSIGEMT - Term Emulator trap\nSIGFPE P1990 Core Floating-point exception\nSIGHUP P1990 Term Hangup detected on controlling terminal\nor death of controlling process\nSIGILL P1990 Core Illegal Instruction\nSIGINFO - A synonym for SIGPWR\nSIGINT P1990 Term Interrupt from keyboard\nSIGIO - Term I/O now possible (4.2BSD)\nSIGIOT - Core IOT trap. A synonym for SIGABRT\nSIGKILL P1990 Term Kill signal\nSIGLOST - Term File lock lost (unused)\nSIGPIPE P1990 Term Broken pipe: write to pipe with no\nreaders; see pipe(7)\nSIGPOLL P2001 Term Pollable event (Sys V);\nsynonym for SIGIO\nSIGPROF P2001 Term Profiling timer expired\nSIGPWR - Term Power failure (System V)\nSIGQUIT P1990 Core Quit from keyboard\nSIGSEGV P1990 Core Invalid memory reference\nSIGSTKFLT - Term Stack fault on coprocessor (unused)\nSIGSTOP P1990 Stop Stop process\nSIGTSTP P1990 Stop Stop typed at terminal\nSIGSYS P2001 Core Bad system call (SVr4);\nsee also seccomp(2)\nSIGTERM P1990 Term Termination signal\nSIGTRAP P2001 Core Trace/breakpoint trap\nSIGTTIN P1990 Stop Terminal input for background process\nSIGTTOU P1990 Stop Terminal output for background process\nSIGUNUSED - Core Synonymous with SIGSYS\nSIGURG P2001 Ign Urgent condition on socket (4.2BSD)\nSIGUSR1 P1990 Term User-defined signal 1\nSIGUSR2 P1990 Term User-defined signal 2\nSIGVTALRM P2001 Term Virtual alarm clock (4.2BSD)\nSIGXCPU P2001 Core CPU time limit exceeded (4.2BSD);\nsee setrlimit(2)\nSIGXFSZ P2001 Core File size limit exceeded (4.2BSD);\nsee setrlimit(2)\nSIGWINCH - Ign Window resize signal (4.3BSD, Sun)\n\nThe signals SIGKILL and SIGSTOP cannot be caught, blocked, or ignored.\n\nUp to and including Linux 2.2, the default behavior for SIGSYS, SIGXCPU, SIGXFSZ, and (on ar‐\nchitectures other than SPARC and MIPS) SIGBUS was to terminate the process (without a core\ndump). (On some other UNIX systems the default action for SIGXCPU and SIGXFSZ is to termi‐\nnate the process without a core dump.) Linux 2.4 conforms to the POSIX.1-2001 requirements\nfor these signals, terminating the process with a core dump.\n\nSIGEMT is not specified in POSIX.1-2001, but nevertheless appears on most other UNIX systems,\nwhere its default action is typically to terminate the process with a core dump.\n\nSIGPWR (which is not specified in POSIX.1-2001) is typically ignored by default on those\nother UNIX systems where it appears.\n\nSIGIO (which is not specified in POSIX.1-2001) is ignored by default on several other UNIX\nsystems.\n" }, { "name": "Queueing and delivery semantics for standard signals", "content": "If multiple standard signals are pending for a process, the order in which the signals are\ndelivered is unspecified.\n\nStandard signals do not queue. If multiple instances of a standard signal are generated\nwhile that signal is blocked, then only one instance of the signal is marked as pending (and\nthe signal will be delivered just once when it is unblocked). In the case where a standard\nsignal is already pending, the siginfot structure (see sigaction(2)) associated with that\nsignal is not overwritten on arrival of subsequent instances of the same signal. Thus, the\nprocess will receive the information associated with the first instance of the signal.\n" }, { "name": "Signal numbering for standard signals", "content": "The numeric value for each signal is given in the table below. As shown in the table, many\nsignals have different numeric values on different architectures. The first numeric value in\neach table row shows the signal number on x86, ARM, and most other architectures; the second\nvalue is for Alpha and SPARC; the third is for MIPS; and the last is for PARISC. A dash (-)\ndenotes that a signal is absent on the corresponding architecture.\n\nSignal x86/ARM Alpha/ MIPS PARISC Notes\nmost others SPARC\n─────────────────────────────────────────────────────────────────\nSIGHUP 1 1 1 1\nSIGINT 2 2 2 2\nSIGQUIT 3 3 3 3\nSIGILL 4 4 4 4\nSIGTRAP 5 5 5 5\nSIGABRT 6 6 6 6\nSIGIOT 6 6 6 6\nSIGBUS 7 10 10 10\nSIGEMT - 7 7 -\nSIGFPE 8 8 8 8\nSIGKILL 9 9 9 9\nSIGUSR1 10 30 16 16\nSIGSEGV 11 11 11 11\nSIGUSR2 12 31 17 17\nSIGPIPE 13 13 13 13\nSIGALRM 14 14 14 14\nSIGTERM 15 15 15 15\nSIGSTKFLT 16 - - 7\nSIGCHLD 17 20 18 18\nSIGCLD - - 18 -\nSIGCONT 18 19 25 26\nSIGSTOP 19 17 23 24\nSIGTSTP 20 18 24 25\nSIGTTIN 21 21 26 27\nSIGTTOU 22 22 27 28\nSIGURG 23 16 21 29\nSIGXCPU 24 24 30 12\nSIGXFSZ 25 25 31 30\nSIGVTALRM 26 26 28 20\nSIGPROF 27 27 29 21\nSIGWINCH 28 28 20 23\nSIGIO 29 23 22 22\nSIGPOLL Same as SIGIO\nSIGPWR 30 29/- 19 19\nSIGINFO - 29/- - -\nSIGLOST - -/29 - -\nSIGSYS 31 12 12 31\nSIGUNUSED 31 - - 31\n\nNote the following:\n\n* Where defined, SIGUNUSED is synonymous with SIGSYS. Since glibc 2.26, SIGUNUSED is no\nlonger defined on any architecture.\n\n* Signal 29 is SIGINFO/SIGPWR (synonyms for the same value) on Alpha but SIGLOST on SPARC.\n" }, { "name": "Real-time signals", "content": "Starting with version 2.2, Linux supports real-time signals as originally defined in the\nPOSIX.1b real-time extensions (and now included in POSIX.1-2001). The range of supported\nreal-time signals is defined by the macros SIGRTMIN and SIGRTMAX. POSIX.1-2001 requires that\nan implementation support at least POSIXRTSIGMAX (8) real-time signals.\n\nThe Linux kernel supports a range of 33 different real-time signals, numbered 32 to 64. How‐\never, the glibc POSIX threads implementation internally uses two (for NPTL) or three (for\nLinuxThreads) real-time signals (see pthreads(7)), and adjusts the value of SIGRTMIN suitably\n(to 34 or 35). Because the range of available real-time signals varies according to the\nglibc threading implementation (and this variation can occur at run time according to the\navailable kernel and glibc), and indeed the range of real-time signals varies across UNIX\nsystems, programs should never refer to real-time signals using hard-coded numbers, but in‐\nstead should always refer to real-time signals using the notation SIGRTMIN+n, and include\nsuitable (run-time) checks that SIGRTMIN+n does not exceed SIGRTMAX.\n\nUnlike standard signals, real-time signals have no predefined meanings: the entire set of\nreal-time signals can be used for application-defined purposes.\n\nThe default action for an unhandled real-time signal is to terminate the receiving process.\n\nReal-time signals are distinguished by the following:\n\n1. Multiple instances of real-time signals can be queued. By contrast, if multiple in‐\nstances of a standard signal are delivered while that signal is currently blocked, then\nonly one instance is queued.\n\n2. If the signal is sent using sigqueue(3), an accompanying value (either an integer or a\npointer) can be sent with the signal. If the receiving process establishes a handler for\nthis signal using the SASIGINFO flag to sigaction(2), then it can obtain this data via\nthe sivalue field of the siginfot structure passed as the second argument to the han‐\ndler. Furthermore, the sipid and siuid fields of this structure can be used to obtain\nthe PID and real user ID of the process sending the signal.\n\n3. Real-time signals are delivered in a guaranteed order. Multiple real-time signals of the\nsame type are delivered in the order they were sent. If different real-time signals are\nsent to a process, they are delivered starting with the lowest-numbered signal. (I.e.,\nlow-numbered signals have highest priority.) By contrast, if multiple standard signals\nare pending for a process, the order in which they are delivered is unspecified.\n\nIf both standard and real-time signals are pending for a process, POSIX leaves it unspecified\nwhich is delivered first. Linux, like many other implementations, gives priority to standard\nsignals in this case.\n\nAccording to POSIX, an implementation should permit at least POSIXSIGQUEUEMAX (32) real-\ntime signals to be queued to a process. However, Linux does things differently. In kernels\nup to and including 2.6.7, Linux imposes a system-wide limit on the number of queued real-\ntime signals for all processes. This limit can be viewed and (with privilege) changed via\nthe /proc/sys/kernel/rtsig-max file. A related file, /proc/sys/kernel/rtsig-nr, can be used\nto find out how many real-time signals are currently queued. In Linux 2.6.8, these /proc in‐\nterfaces were replaced by the RLIMITSIGPENDING resource limit, which specifies a per-user\nlimit for queued signals; see setrlimit(2) for further details.\n\nThe addition of real-time signals required the widening of the signal set structure\n(sigsett) from 32 to 64 bits. Consequently, various system calls were superseded by new\nsystem calls that supported the larger signal sets. The old and new system calls are as fol‐\nlows:\n" }, { "name": "Linux 2.0 and earlier Linux 2.2 and later", "content": "sigaction(2) rtsigaction(2)\nsigpending(2) rtsigpending(2)\nsigprocmask(2) rtsigprocmask(2)\nsigreturn(2) rtsigreturn(2)\nsigsuspend(2) rtsigsuspend(2)\nsigtimedwait(2) rtsigtimedwait(2)\n" }, { "name": "Interruption of system calls and library functions by signal handlers", "content": "If a signal handler is invoked while a system call or library function call is blocked, then\neither:\n\n* the call is automatically restarted after the signal handler returns; or\n\n* the call fails with the error EINTR.\n\nWhich of these two behaviors occurs depends on the interface and whether or not the signal\nhandler was established using the SARESTART flag (see sigaction(2)). The details vary\nacross UNIX systems; below, the details for Linux.\n\nIf a blocked call to one of the following interfaces is interrupted by a signal handler, then\nthe call is automatically restarted after the signal handler returns if the SARESTART flag\nwas used; otherwise the call fails with the error EINTR:\n\n* read(2), readv(2), write(2), writev(2), and ioctl(2) calls on \"slow\" devices. A \"slow\" de‐\nvice is one where the I/O call may block for an indefinite time, for example, a terminal,\npipe, or socket. If an I/O call on a slow device has already transferred some data by the\ntime it is interrupted by a signal handler, then the call will return a success status\n(normally, the number of bytes transferred). Note that a (local) disk is not a slow device\naccording to this definition; I/O operations on disk devices are not interrupted by sig‐\nnals.\n\n* open(2), if it can block (e.g., when opening a FIFO; see fifo(7)).\n\n* wait(2), wait3(2), wait4(2), waitid(2), and waitpid(2).\n\n* Socket interfaces: accept(2), connect(2), recv(2), recvfrom(2), recvmmsg(2), recvmsg(2),\nsend(2), sendto(2), and sendmsg(2), unless a timeout has been set on the socket (see be‐\nlow).\n\n* File locking interfaces: flock(2) and the FSETLKW and FOFDSETLKW operations of fcntl(2)\n\n* POSIX message queue interfaces: mqreceive(3), mqtimedreceive(3), mqsend(3), and\nmqtimedsend(3).\n\n* futex(2) FUTEXWAIT (since Linux 2.6.22; beforehand, always failed with EINTR).\n\n* getrandom(2).\n\n* pthreadmutexlock(3), pthreadcondwait(3), and related APIs.\n\n* futex(2) FUTEXWAITBITSET.\n\n* POSIX semaphore interfaces: semwait(3) and semtimedwait(3) (since Linux 2.6.22; before‐\nhand, always failed with EINTR).\n\n* read(2) from an inotify(7) file descriptor (since Linux 3.8; beforehand, always failed with\nEINTR).\n\nThe following interfaces are never restarted after being interrupted by a signal handler, re‐\ngardless of the use of SARESTART; they always fail with the error EINTR when interrupted by\na signal handler:\n\n* \"Input\" socket interfaces, when a timeout (SORCVTIMEO) has been set on the socket using\nsetsockopt(2): accept(2), recv(2), recvfrom(2), recvmmsg(2) (also with a non-NULL timeout\nargument), and recvmsg(2).\n\n* \"Output\" socket interfaces, when a timeout (SORCVTIMEO) has been set on the socket using\nsetsockopt(2): connect(2), send(2), sendto(2), and sendmsg(2).\n\n* Interfaces used to wait for signals: pause(2), sigsuspend(2), sigtimedwait(2), and sigwait‐‐\ninfo(2).\n\n* File descriptor multiplexing interfaces: epollwait(2), epollpwait(2), poll(2), ppoll(2),\nselect(2), and pselect(2).\n\n* System V IPC interfaces: msgrcv(2), msgsnd(2), semop(2), and semtimedop(2).\n\n* Sleep interfaces: clocknanosleep(2), nanosleep(2), and usleep(3).\n\n* iogetevents(2).\n\nThe sleep(3) function is also never restarted if interrupted by a handler, but gives a suc‐\ncess return: the number of seconds remaining to sleep.\n" }, { "name": "Interruption of system calls and library functions by stop signals", "content": "On Linux, even in the absence of signal handlers, certain blocking interfaces can fail with\nthe error EINTR after the process is stopped by one of the stop signals and then resumed via\nSIGCONT. This behavior is not sanctioned by POSIX.1, and doesn't occur on other systems.\n\nThe Linux interfaces that display this behavior are:\n\n* \"Input\" socket interfaces, when a timeout (SORCVTIMEO) has been set on the socket using\nsetsockopt(2): accept(2), recv(2), recvfrom(2), recvmmsg(2) (also with a non-NULL timeout\nargument), and recvmsg(2).\n\n* \"Output\" socket interfaces, when a timeout (SORCVTIMEO) has been set on the socket using\nsetsockopt(2): connect(2), send(2), sendto(2), and sendmsg(2), if a send timeout (SOSND‐‐\nTIMEO) has been set.\n\n* epollwait(2), epollpwait(2).\n\n* semop(2), semtimedop(2).\n\n* sigtimedwait(2), sigwaitinfo(2).\n\n* Linux 3.7 and earlier: read(2) from an inotify(7) file descriptor\n\n* Linux 2.6.21 and earlier: futex(2) FUTEXWAIT, semtimedwait(3), semwait(3).\n\n* Linux 2.6.8 and earlier: msgrcv(2), msgsnd(2).\n\n* Linux 2.4 and earlier: nanosleep(2).\n" } ] }, "CONFORMING TO": { "content": "POSIX.1, except as noted.\n", "subsections": [] }, "NOTES": { "content": "For a discussion of async-signal-safe functions, see signal-safety(7).\n\nThe /proc/[pid]/task/[tid]/status file contains various fields that show the signals that a\nthread is blocking (SigBlk), catching (SigCgt), or ignoring (SigIgn). (The set of signals\nthat are caught or ignored will be the same across all threads in a process.) Other fields\nshow the set of pending signals that are directed to the thread (SigPnd) as well as the set\nof pending signals that are directed to the process as a whole (ShdPnd). The corresponding\nfields in /proc/[pid]/status show the information for the main thread. See proc(5) for fur‐\nther details.\n", "subsections": [] }, "BUGS": { "content": "There are six signals that can be delivered as a consequence of a hardware exception: SIGBUS,\nSIGEMT, SIGFPE, SIGILL, SIGSEGV, and SIGTRAP. Which of these signals is delivered, for any\ngiven hardware exception, is not documented and does not always make sense.\n\nFor example, an invalid memory access that causes delivery of SIGSEGV on one CPU architecture\nmay cause delivery of SIGBUS on another architecture, or vice versa.\n\nFor another example, using the x86 int instruction with a forbidden argument (any number\nother than 3 or 128) causes delivery of SIGSEGV, even though SIGILL would make more sense,\nbecause of how the CPU reports the forbidden operation to the kernel.\n", "subsections": [] }, "SEE ALSO": { "content": "kill(1), clone(2), getrlimit(2), kill(2), pidfdsendsignal(2), restartsyscall(2),\nrtsigqueueinfo(2), setitimer(2), setrlimit(2), sgetmask(2), sigaction(2), sigaltstack(2),\nsignal(2), signalfd(2), sigpending(2), sigprocmask(2), sigreturn(2), sigsuspend(2), sigwait‐‐\ninfo(2), abort(3), bsdsignal(3), killpg(3), longjmp(3), pthreadsigqueue(3), raise(3),\nsigqueue(3), sigset(3), sigsetops(3), sigvec(3), sigwait(3), strsignal(3), swapcontext(3),\nsysvsignal(3), core(5), proc(5), nptl(7), pthreads(7), sigevent(7)\n", "subsections": [] }, "COLOPHON": { "content": "This page is part of release 5.10 of the Linux man-pages project. A description of the\nproject, information about reporting bugs, and the latest version of this page, can be found\nat https://www.kernel.org/doc/man-pages/.\n\n\n\nLinux 2020-12-21 SIGNAL(7)", "subsections": [] } }, "summary": "signal - overview of signals", "flags": [], "examples": [], "see_also": [ { "name": "kill", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/kill/1/json" }, { "name": "clone", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/clone/2/json" }, { "name": "getrlimit", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/getrlimit/2/json" }, { "name": "kill", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/kill/2/json" }, { "name": "pidfdsendsignal", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/pidfdsendsignal/2/json" }, { "name": "restartsyscall", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/restartsyscall/2/json" }, { "name": "rtsigqueueinfo", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/rtsigqueueinfo/2/json" }, { "name": "setitimer", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/setitimer/2/json" }, { "name": "setrlimit", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/setrlimit/2/json" }, { "name": "sgetmask", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sgetmask/2/json" }, { "name": "sigaction", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sigaction/2/json" }, { "name": "sigaltstack", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sigaltstack/2/json" }, { "name": "signalfd", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/signalfd/2/json" }, { "name": "sigpending", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sigpending/2/json" }, { "name": "sigprocmask", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sigprocmask/2/json" }, { "name": "sigreturn", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sigreturn/2/json" }, { "name": "sigsuspend", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/sigsuspend/2/json" }, { "name": "info", "section": "2", "url": "https://www.chedong.com/phpMan.php/man/info/2/json" }, { "name": "abort", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/abort/3/json" }, { "name": "bsdsignal", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/bsdsignal/3/json" }, { "name": "killpg", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/killpg/3/json" }, { "name": "longjmp", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/longjmp/3/json" }, { "name": "pthreadsigqueue", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/pthreadsigqueue/3/json" }, { "name": "raise", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/raise/3/json" }, { "name": "sigqueue", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/sigqueue/3/json" }, { "name": "sigset", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/sigset/3/json" }, { "name": "sigsetops", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/sigsetops/3/json" }, { "name": "sigvec", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/sigvec/3/json" }, { "name": "sigwait", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/sigwait/3/json" }, { "name": "strsignal", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/strsignal/3/json" }, { "name": "swapcontext", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/swapcontext/3/json" }, { "name": "sysvsignal", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/sysvsignal/3/json" }, { "name": "core", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/core/5/json" }, { "name": "proc", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/proc/5/json" }, { "name": "nptl", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/nptl/7/json" }, { "name": "pthreads", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/pthreads/7/json" }, { "name": "sigevent", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/sigevent/7/json" } ], "tldr": { "source": "official", "description": "Simplified software signal facilities.", "examples": [ { "description": "View documentation for signals in macOS", "command": "man signal" } ] } }