sigaction(2) — Linux manual page

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sigaction(2)               System Calls Manual               sigaction(2)

NAME         top

       sigaction, rt_sigaction - examine and change a signal action

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <signal.h>

       int sigaction(int signum,
                     const struct sigaction *_Nullable restrict act,
                     struct sigaction *_Nullable restrict oldact);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       sigaction():
           _POSIX_C_SOURCE

       siginfo_t:
           _POSIX_C_SOURCE >= 199309L

DESCRIPTION         top

       The sigaction() system call is used to change the action taken by
       a process on receipt of a specific signal.  (See signal(7) for an
       overview of signals.)

       signum specifies the signal and can be any valid signal except
       SIGKILL and SIGSTOP.

       If act is non-NULL, the new action for signal signum is installed
       from act.  If oldact is non-NULL, the previous action is saved in
       oldact.

       The sigaction structure is defined as something like:

           struct sigaction {
               void     (*sa_handler)(int);
               void     (*sa_sigaction)(int, siginfo_t *, void *);
               sigset_t   sa_mask;
               int        sa_flags;
               void     (*sa_restorer)(void);
           };

       On some architectures a union is involved: do not assign to both
       sa_handler and sa_sigaction.

       The sa_restorer field is not intended for application use.  (POSIX
       does not specify a sa_restorer field.)  Some further details of
       the purpose of this field can be found in sigreturn(2).

       sa_handler specifies the action to be associated with signum and
       can be one of the following:

       •  SIG_DFL for the default action.

       •  SIG_IGN to ignore this signal.

       •  A pointer to a signal handling function.  This function
          receives the signal number as its only argument.

       If SA_SIGINFO is specified in sa_flags, then sa_sigaction (instead
       of sa_handler) specifies the signal-handling function for signum.
       This function receives three arguments, as described below.

       sa_mask specifies a mask of signals which should be blocked (i.e.,
       added to the signal mask of the thread in which the signal handler
       is invoked) during execution of the signal handler.  In addition,
       the signal which triggered the handler will be blocked, unless the
       SA_NODEFER flag is used.

       sa_flags specifies a set of flags which modify the behavior of the
       signal.  It is formed by the bitwise OR of zero or more of the
       following:

       SA_NOCLDSTOP
              If signum is SIGCHLD, do not receive notification when
              child processes stop (i.e., when they receive one of
              SIGSTOP, SIGTSTP, SIGTTIN, or SIGTTOU) or resume (i.e.,
              they receive SIGCONT) (see wait(2)).  This flag is
              meaningful only when establishing a handler for SIGCHLD.

       SA_NOCLDWAIT (since Linux 2.6)
              If signum is SIGCHLD, do not transform children into
              zombies when they terminate.  See also waitpid(2).  This
              flag is meaningful only when establishing a handler for
              SIGCHLD, or when setting that signal's disposition to
              SIG_DFL.

              If the SA_NOCLDWAIT flag is set when establishing a handler
              for SIGCHLD, POSIX.1 leaves it unspecified whether a
              SIGCHLD signal is generated when a child process
              terminates.  On Linux, a SIGCHLD signal is generated in
              this case; on some other implementations, it is not.

       SA_NODEFER
              Do not add the signal to the thread's signal mask while the
              handler is executing, unless the signal is specified in
              act.sa_mask.  Consequently, a further instance of the
              signal may be delivered to the thread while it is executing
              the handler.  This flag is meaningful only when
              establishing a signal handler.

              SA_NOMASK is an obsolete, nonstandard synonym for this
              flag.

       SA_ONSTACK
              Call the signal handler on an alternate signal stack
              provided by sigaltstack(2).  If an alternate stack is not
              available, the default stack will be used.  This flag is
              meaningful only when establishing a signal handler.

       SA_RESETHAND
              Restore the signal action to the default upon entry to the
              signal handler.  This flag is meaningful only when
              establishing a signal handler.

              SA_ONESHOT is an obsolete, nonstandard synonym for this
              flag.

       SA_RESTART
              Provide behavior compatible with BSD signal semantics by
              making certain system calls restartable across signals.
              This flag is meaningful only when establishing a signal
              handler.  See signal(7) for a discussion of system call
              restarting.

       SA_RESTORER
              Not intended for application use.  This flag is used by C
              libraries to indicate that the sa_restorer field contains
              the address of a "signal trampoline".  See sigreturn(2) for
              more details.

       SA_SIGINFO (since Linux 2.2)
              The signal handler takes three arguments, not one.  In this
              case, sa_sigaction should be set instead of sa_handler.
              This flag is meaningful only when establishing a signal
              handler.

       SA_UNSUPPORTED (since Linux 5.11)
              Used to dynamically probe for flag bit support.

              If an attempt to register a handler succeeds with this flag
              set in act->sa_flags alongside other flags that are
              potentially unsupported by the kernel, and an immediately
              subsequent sigaction() call specifying the same signal
              number and with a non-NULL oldact argument yields
              SA_UNSUPPORTED clear in oldact->sa_flags, then
              oldact->sa_flags may be used as a bitmask describing which
              of the potentially unsupported flags are, in fact,
              supported.  See the section "Dynamically probing for flag
              bit support" below for more details.

       SA_EXPOSE_TAGBITS (since Linux 5.11)
              Normally, when delivering a signal, an architecture-
              specific set of tag bits are cleared from the si_addr field
              of siginfo_t.  If this flag is set, an architecture-
              specific subset of the tag bits will be preserved in
              si_addr.

              Programs that need to be compatible with Linux versions
              older than 5.11 must use SA_UNSUPPORTED to probe for
              support.

   The siginfo_t argument to a SA_SIGINFO handler
       When the SA_SIGINFO flag is specified in act.sa_flags, the signal
       handler address is passed via the act.sa_sigaction field.  This
       handler takes three arguments, as follows:

           void
           handler(int sig, siginfo_t *info, void *ucontext)
           {
               ...
           }

       These three arguments are as follows

       sig    The number of the signal that caused invocation of the
              handler.

       info   A pointer to a siginfo_t, which is a structure containing
              further information about the signal, as described below.

       ucontext
              This is a pointer to a ucontext_t structure, cast to
              void *.  The structure pointed to by this field contains
              signal context information that was saved on the user-space
              stack by the kernel; for details, see sigreturn(2).
              Further information about the ucontext_t structure can be
              found in getcontext(3) and signal(7).  Commonly, the
              handler function doesn't make any use of the third
              argument.

       The siginfo_t data type is a structure with the following fields:

           siginfo_t {
               int      si_signo;     /* Signal number */
               int      si_errno;     /* An errno value */
               int      si_code;      /* Signal code */
               int      si_trapno;    /* Trap number that caused
                                         hardware-generated signal
                                         (unused on most architectures) */
               pid_t    si_pid;       /* Sending process ID */
               uid_t    si_uid;       /* Real user ID of sending process */
               int      si_status;    /* Exit value or signal */
               clock_t  si_utime;     /* User time consumed */
               clock_t  si_stime;     /* System time consumed */
               union sigval si_value; /* Signal value */
               int      si_int;       /* POSIX.1b signal */
               void    *si_ptr;       /* POSIX.1b signal */
               int      si_overrun;   /* Timer overrun count;
                                         POSIX.1b timers */
               int      si_timerid;   /* Timer ID; POSIX.1b timers */
               void    *si_addr;      /* Memory location which caused fault */
               long     si_band;      /* Band event (was int in
                                         glibc 2.3.2 and earlier) */
               int      si_fd;        /* File descriptor */
               short    si_addr_lsb;  /* Least significant bit of address
                                         (since Linux 2.6.32) */
               void    *si_lower;     /* Lower bound when address violation
                                         occurred (since Linux 3.19) */
               void    *si_upper;     /* Upper bound when address violation
                                         occurred (since Linux 3.19) */
               int      si_pkey;      /* Protection key on PTE that caused
                                         fault (since Linux 4.6) */
               void    *si_call_addr; /* Address of system call instruction
                                         (since Linux 3.5) */
               int      si_syscall;   /* Number of attempted system call
                                         (since Linux 3.5) */
               unsigned int si_arch;  /* Architecture of attempted system call
                                         (since Linux 3.5) */
           }

       si_signo, si_errno and si_code are defined for all signals.
       (si_errno is generally unused on Linux.)  The rest of the struct
       may be a union, so that one should read only the fields that are
       meaningful for the given signal:

       •  Signals sent with kill(2) and sigqueue(3) fill in si_pid and
          si_uid.  In addition, signals sent with sigqueue(3) fill in
          si_int and si_ptr with the values specified by the sender of
          the signal; see sigqueue(3) for more details.

       •  Signals sent by POSIX.1b timers (since Linux 2.6) fill in
          si_overrun and si_timerid.  The si_timerid field is an internal
          ID used by the kernel to identify the timer; it is not the same
          as the timer ID returned by timer_create(2).  The si_overrun
          field is the timer overrun count; this is the same information
          as is obtained by a call to timer_getoverrun(2).  These fields
          are nonstandard Linux extensions.

       •  Signals sent for message queue notification (see the
          description of SIGEV_SIGNAL in mq_notify(3)) fill in
          si_int/si_ptr, with the sigev_value supplied to mq_notify(3);
          si_pid, with the process ID of the message sender; and si_uid,
          with the real user ID of the message sender.

       •  SIGCHLD fills in si_pid, si_uid, si_status, si_utime, and
          si_stime, providing information about the child.  The si_pid
          field is the process ID of the child; si_uid is the child's
          real user ID.  The si_status field contains the exit status of
          the child (if si_code is CLD_EXITED), or the signal number that
          caused the process to change state.  The si_utime and si_stime
          contain the user and system CPU time used by the child process;
          these fields do not include the times used by waited-for
          children (unlike getrusage(2) and times(2)).  Up to Linux 2.6,
          and since Linux 2.6.27, these fields report CPU time in units
          of sysconf(_SC_CLK_TCK).  In Linux 2.6 kernels before Linux
          2.6.27, a bug meant that these fields reported time in units of
          the (configurable) system jiffy (see time(7)).

       •  SIGILL, SIGFPE, SIGSEGV, SIGBUS, and SIGTRAP fill in si_addr
          with the address of the fault.  On some architectures, these
          signals also fill in the si_trapno field.

          Some suberrors of SIGBUS, in particular BUS_MCEERR_AO and
          BUS_MCEERR_AR, also fill in si_addr_lsb.  This field indicates
          the least significant bit of the reported address and therefore
          the extent of the corruption.  For example, if a full page was
          corrupted, si_addr_lsb contains log2(sysconf(_SC_PAGESIZE)).
          When SIGTRAP is delivered in response to a ptrace(2) event
          (PTRACE_EVENT_foo), si_addr is not populated, but si_pid and
          si_uid are populated with the respective process ID and user ID
          responsible for delivering the trap.  In the case of
          seccomp(2), the tracee will be shown as delivering the event.
          BUS_MCEERR_* and si_addr_lsb are Linux-specific extensions.

          The SEGV_BNDERR suberror of SIGSEGV populates si_lower and
          si_upper.

          The SEGV_PKUERR suberror of SIGSEGV populates si_pkey.

       •  SIGIO/SIGPOLL (the two names are synonyms on Linux) fills in
          si_band and si_fd.  The si_band event is a bit mask containing
          the same values as are filled in the revents field by poll(2).
          The si_fd field indicates the file descriptor for which the I/O
          event occurred; for further details, see the description of
          F_SETSIG in fcntl(2).

       •  SIGSYS, generated (since Linux 3.5) when a seccomp filter
          returns SECCOMP_RET_TRAP, fills in si_call_addr, si_syscall,
          si_arch, si_errno, and other fields as described in seccomp(2).

   The si_code field
       The si_code field inside the siginfo_t argument that is passed to
       a SA_SIGINFO signal handler is a value (not a bit mask) indicating
       why this signal was sent.  For a ptrace(2) event, si_code will
       contain SIGTRAP and have the ptrace event in the high byte:

           (SIGTRAP | PTRACE_EVENT_foo << 8).

       For a non-ptrace(2) event, the values that can appear in si_code
       are described in the remainder of this section.  Since glibc 2.20,
       the definitions of most of these symbols are obtained from
       <signal.h> by defining feature test macros (before including any
       header file) as follows:

       •  _XOPEN_SOURCE with the value 500 or greater;

       •  _XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED; or

       •  _POSIX_C_SOURCE with the value 200809L or greater.

       For the TRAP_* constants, the symbol definitions are provided only
       in the first two cases.  Before glibc 2.20, no feature test macros
       were required to obtain these symbols.

       For a regular signal, the following list shows the values which
       can be placed in si_code for any signal, along with the reason
       that the signal was generated.

           SI_USER
                  kill(2).

           SI_KERNEL
                  Sent by the kernel.

           SI_QUEUE
                  sigqueue(3).

           SI_TIMER
                  POSIX, or setitimer(2) or alarm(2) timer expired.

           SI_MESGQ (since Linux 2.6.6)
                  POSIX message queue state changed; see mq_notify(3).

           SI_ASYNCIO
                  AIO completed.

           SI_SIGIO
                  Queued SIGIO (only up to Linux 2.2; from Linux 2.4
                  onward SIGIO/SIGPOLL fills in si_code as described
                  below).

           SI_TKILL (since Linux 2.4.19)
                  tkill(2) or tgkill(2).

       The following values can be placed in si_code for a SIGILL signal:

           ILL_ILLOPC
                  Illegal opcode.

           ILL_ILLOPN
                  Illegal operand.

           ILL_ILLADR
                  Illegal addressing mode.

           ILL_ILLTRP
                  Illegal trap.

           ILL_PRVOPC
                  Privileged opcode.

           ILL_PRVREG
                  Privileged register.

           ILL_COPROC
                  Coprocessor error.

           ILL_BADSTK
                  Internal stack error.

       The following values can be placed in si_code for a SIGFPE signal:

           FPE_INTDIV
                  Integer divide by zero.

           FPE_INTOVF
                  Integer overflow.

           FPE_FLTDIV
                  Floating-point divide by zero.

           FPE_FLTOVF
                  Floating-point overflow.

           FPE_FLTUND
                  Floating-point underflow.

           FPE_FLTRES
                  Floating-point inexact result.

           FPE_FLTINV
                  Floating-point invalid operation.

           FPE_FLTSUB
                  Subscript out of range.

       The following values can be placed in si_code for a SIGSEGV
       signal:

           SEGV_MAPERR
                  Address not mapped to object.

           SEGV_ACCERR
                  Invalid permissions for mapped object.

           SEGV_BNDERR (since Linux 3.19)
                  Failed address bound checks.

           SEGV_PKUERR (since Linux 4.6)
                  Access was denied by memory protection keys.  See
                  pkeys(7).  The protection key which applied to this
                  access is available via si_pkey.

       The following values can be placed in si_code for a SIGBUS signal:

           BUS_ADRALN
                  Invalid address alignment.

           BUS_ADRERR
                  Nonexistent physical address.

           BUS_OBJERR
                  Object-specific hardware error.

           BUS_MCEERR_AR (since Linux 2.6.32)
                  Hardware memory error consumed on a machine check;
                  action required.

           BUS_MCEERR_AO (since Linux 2.6.32)
                  Hardware memory error detected in process but not
                  consumed; action optional.

       The following values can be placed in si_code for a SIGTRAP
       signal:

           TRAP_BRKPT
                  Process breakpoint.

           TRAP_TRACE
                  Process trace trap.

           TRAP_BRANCH (since Linux 2.4, IA64 only)
                  Process taken branch trap.

           TRAP_HWBKPT (since Linux 2.4, IA64 only)
                  Hardware breakpoint/watchpoint.

       The following values can be placed in si_code for a SIGCHLD
       signal:

           CLD_EXITED
                  Child has exited.

           CLD_KILLED
                  Child was killed.

           CLD_DUMPED
                  Child terminated abnormally.

           CLD_TRAPPED
                  Traced child has trapped.

           CLD_STOPPED
                  Child has stopped.

           CLD_CONTINUED (since Linux 2.6.9)
                  Stopped child has continued.

       The following values can be placed in si_code for a SIGIO/SIGPOLL
       signal:

           POLL_IN
                  Data input available.

           POLL_OUT
                  Output buffers available.

           POLL_MSG
                  Input message available.

           POLL_ERR
                  I/O error.

           POLL_PRI
                  High priority input available.

           POLL_HUP
                  Device disconnected.

       The following value can be placed in si_code for a SIGSYS signal:

           SYS_SECCOMP (since Linux 3.5)
                  Triggered by a seccomp(2) filter rule.

   Dynamically probing for flag bit support
       The sigaction() call on Linux accepts unknown bits set in
       act->sa_flags without error.  The behavior of the kernel starting
       with Linux 5.11 is that a second sigaction() will clear unknown
       bits from oldact->sa_flags.  However, historically, a second
       sigaction() call would typically leave those bits set in
       oldact->sa_flags.

       This means that support for new flags cannot be detected simply by
       testing for a flag in sa_flags, and a program must test that
       SA_UNSUPPORTED has been cleared before relying on the contents of
       sa_flags.

       Since the behavior of the signal handler cannot be guaranteed
       unless the check passes, it is wise to either block the affected
       signal while registering the handler and performing the check in
       this case, or where this is not possible, for example if the
       signal is synchronous, to issue the second sigaction() in the
       signal handler itself.

       In kernels that do not support a specific flag, the kernel's
       behavior is as if the flag was not set, even if the flag was set
       in act->sa_flags.

       The flags SA_NOCLDSTOP, SA_NOCLDWAIT, SA_SIGINFO, SA_ONSTACK,
       SA_RESTART, SA_NODEFER, SA_RESETHAND, and, if defined by the
       architecture, SA_RESTORER may not be reliably probed for using
       this mechanism, because they were introduced before Linux 5.11.
       However, in general, programs may assume that these flags are
       supported, since they have all been supported since Linux 2.6,
       which was released in the year 2003.

       See EXAMPLES below for a demonstration of the use of
       SA_UNSUPPORTED.

RETURN VALUE         top

       sigaction() returns 0 on success; on error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

       EFAULT act or oldact points to memory which is not a valid part of
              the process address space.

       EINVAL An invalid signal was specified.  This will also be
              generated if an attempt is made to change the action for
              SIGKILL or SIGSTOP, which cannot be caught or ignored.

VERSIONS         top

   C library/kernel differences
       The glibc wrapper function for sigaction() gives an error (EINVAL)
       on attempts to change the disposition of the two real-time signals
       used internally by the NPTL threading implementation.  See nptl(7)
       for details.

       On architectures where the signal trampoline resides in the C
       library, the glibc wrapper function for sigaction() places the
       address of the trampoline code in the act.sa_restorer field and
       sets the SA_RESTORER flag in the act.sa_flags field.  See
       sigreturn(2).

       The original Linux system call was named sigaction().  However,
       with the addition of real-time signals in Linux 2.2, the fixed-
       size, 32-bit sigset_t type supported by that system call was no
       longer fit for purpose.  Consequently, a new system call,
       rt_sigaction(), was added to support an enlarged sigset_t type.
       The new system call takes a fourth argument, size_t sigsetsize,
       which specifies the size in bytes of the signal sets in
       act.sa_mask and oldact.sa_mask.  This argument is currently
       required to have the value sizeof(sigset_t) (or the error EINVAL
       results).  The glibc sigaction() wrapper function hides these
       details from us, transparently calling rt_sigaction() when the
       kernel provides it.

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       POSIX.1-2001, SVr4.

       POSIX.1-1990 disallowed setting the action for SIGCHLD to SIG_IGN.
       POSIX.1-2001 and later allow this possibility, so that ignoring
       SIGCHLD can be used to prevent the creation of zombies (see
       wait(2)).  Nevertheless, the historical BSD and System V behaviors
       for ignoring SIGCHLD differ, so that the only completely portable
       method of ensuring that terminated children do not become zombies
       is to catch the SIGCHLD signal and perform a wait(2) or similar.

       POSIX.1-1990 specified only SA_NOCLDSTOP.  POSIX.1-2001 added
       SA_NOCLDWAIT, SA_NODEFER, SA_ONSTACK, SA_RESETHAND, SA_RESTART,
       and SA_SIGINFO as XSI extensions.  POSIX.1-2008 moved SA_NODEFER,
       SA_RESETHAND, SA_RESTART, and SA_SIGINFO to the base
       specifications.  Use of these latter values in sa_flags may be
       less portable in applications intended for older UNIX
       implementations.

       The SA_RESETHAND flag is compatible with the SVr4 flag of the same
       name.

       The SA_NODEFER flag is compatible with the SVr4 flag of the same
       name under kernels 1.3.9 and later.  On older kernels the Linux
       implementation allowed the receipt of any signal, not just the one
       we are installing (effectively overriding any sa_mask settings).

NOTES         top

       A child created via fork(2) inherits a copy of its parent's signal
       dispositions.  During an execve(2), the dispositions of handled
       signals are reset to the default; the dispositions of ignored
       signals are left unchanged.

       According to POSIX, the behavior of a process is undefined after
       it ignores a SIGFPE, SIGILL, or SIGSEGV signal that was not
       generated by kill(2) or raise(3).  Integer division by zero has
       undefined result.  On some architectures it will generate a SIGFPE
       signal.  (Also dividing the most negative integer by -1 may
       generate SIGFPE.)  Ignoring this signal might lead to an endless
       loop.

       sigaction() can be called with a NULL second argument to query the
       current signal handler.  It can also be used to check whether a
       given signal is valid for the current machine by calling it with
       NULL second and third arguments.

       It is not possible to block SIGKILL or SIGSTOP (by specifying them
       in sa_mask).  Attempts to do so are silently ignored.

       See sigsetops(3) for details on manipulating signal sets.

       See signal-safety(7) for a list of the async-signal-safe functions
       that can be safely called inside from inside a signal handler.

       POSIX only guarantees SI_TIMER for signals created by
       timer_create(2).  Implementations are free to also provide it for
       other types of timers.  The Linux behaviour matches NetBSD.

   Undocumented
       Before the introduction of SA_SIGINFO, it was also possible to get
       some additional information about the signal.  This was done by
       providing an sa_handler signal handler with a second argument of
       type struct sigcontext, which is the same structure as the one
       that is passed in the uc_mcontext field of the ucontext structure
       that is passed (via a pointer) in the third argument of the
       sa_sigaction handler.  See the relevant Linux kernel sources for
       details.  This use is obsolete now.

BUGS         top

       When delivering a signal resulting from a hardware exception with
       a SA_SIGINFO handler, the kernel does not always provide
       meaningful values for all of the fields of the siginfo_t that are
       relevant for that signal.  For example, when the x86 int
       instruction is called with a forbidden argument (any number other
       than 3 or 128), a SIGSEGV signal is delivered, but the siginfo_t
       passed to the signal handler has all its fields besides si_signo
       and si_code set to zero, even if other fields should be set (as an
       example, si_addr should be non-zero for all SIGSEGV signals).

       Up to and including Linux 2.6.13, specifying SA_NODEFER in
       sa_flags prevents not only the delivered signal from being masked
       during execution of the handler, but also the signals specified in
       sa_mask.  This bug was fixed in Linux 2.6.14.

EXAMPLES         top

       See mprotect(2).

   Probing for flag support
       The following example program exits with status EXIT_SUCCESS if
       SA_EXPOSE_TAGBITS is determined to be supported, and EXIT_FAILURE
       otherwise.

       #include <signal.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>

       void
       handler(int signo, siginfo_t *info, void *context)
       {
           struct sigaction oldact;

           if (sigaction(SIGSEGV, NULL, &oldact) == -1
               || (oldact.sa_flags & SA_UNSUPPORTED)
               || !(oldact.sa_flags & SA_EXPOSE_TAGBITS))
           {
               _exit(EXIT_FAILURE);
           }
           _exit(EXIT_SUCCESS);
       }

       int
       main(void)
       {
           struct sigaction act = { 0 };

           act.sa_flags = SA_SIGINFO | SA_UNSUPPORTED | SA_EXPOSE_TAGBITS;
           act.sa_sigaction = &handler;
           if (sigaction(SIGSEGV, &act, NULL) == -1) {
               perror("sigaction");
               exit(EXIT_FAILURE);
           }

           raise(SIGSEGV);
       }

SEE ALSO         top

       kill(1), kill(2), pause(2), pidfd_send_signal(2),
       restart_syscall(2), seccomp(2), sigaltstack(2), signal(2),
       signalfd(2), sigpending(2), sigprocmask(2), sigreturn(2),
       sigsuspend(2), wait(2), killpg(3), raise(3), siginterrupt(3),
       sigqueue(3), sigsetops(3), sigvec(3), core(5), signal(7)

COLOPHON         top

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Linux man-pages 6.10            2024-08-21                   sigaction(2)

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