linux signal-list

Posted 2022-10-15 lcxiao

[root@bogon ~]# kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL
5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE
9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2
13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT
17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU
25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH
29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN
35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3 38) SIGRTMIN+4
39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12
47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14
51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10
55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6
59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX

First the signals described in the original POSIX.1-1990 standard.

       Signal     Value     Action   Comment
       -------------------------------------------------------------------------
       SIGHUP        1       Term    Hangup detected on controlling terminal
                                     or death of controlling process
       SIGINT        2       Term    Interrupt from keyboard
       SIGQUIT       3       Core    Quit from keyboard
       SIGILL        4       Core    Illegal Instruction
       SIGABRT       6       Core    Abort signal from abort(3)
       SIGFPE        8       Core    Floating point exception
       SIGKILL       9       Term    Kill signal
       SIGSEGV      11       Core    Invalid memory reference
       SIGPIPE      13       Term    Broken pipe: write to pipe with no readers
       SIGALRM      14       Term    Timer signal from alarm(2)
       SIGTERM      15       Term    Termination signal
       SIGUSR1   30,10,16    Term    User-defined signal 1
       SIGUSR2   31,12,17    Term    User-defined signal 2
       SIGCHLD   20,17,18    Ign     Child stopped or terminated
       SIGCONT   19,18,25    Cont    Continue if stopped
       SIGSTOP   17,19,23    Stop    Stop process
       SIGTSTP   18,20,24    Stop    Stop typed at tty
       SIGTTIN   21,21,26    Stop    tty input for background process
       SIGTTOU   22,22,27    Stop    tty output for background process

       The signals SIGKILL and SIGSTOP cannot be caught, blocked, or ignored.

       Next the signals not in the POSIX.1-1990 standard but described in SUSv2 and POSIX.1-2001.

Next the signals not in the POSIX.1-1990 standard but described in SUSv2 and POSIX.1-2001.

       Signal       Value     Action   Comment
       -------------------------------------------------------------------------
       SIGBUS      10,7,10     Core    Bus error (bad memory access)
       SIGPOLL                 Term    Pollable event (Sys V). Synonym of SIGIO
       SIGPROF     27,27,29    Term    Profiling timer expired
       SIGSYS      12,-,12     Core    Bad argument to routine (SVr4)
       SIGTRAP        5        Core    Trace/breakpoint trap
       SIGURG      16,23,21    Ign     Urgent condition on socket (4.2BSD)
       SIGVTALRM   26,26,28    Term    Virtual alarm clock (4.2BSD)
       SIGXCPU     24,24,30    Core    CPU time limit exceeded (4.2BSD)
       SIGXFSZ     25,25,31    Core    File size limit exceeded (4.2BSD)

       Up to and including Linux 2.2, the default behaviour for SIGSYS, SIGXCPU,  SIGXFSZ,  and  (on  architectures
       other than SPARC and MIPS) SIGBUS was to terminate the process (without a core dump).  (On some other Unices
       the default action for SIGXCPU and SIGXFSZ is to terminate the process without a core dump.)  Linux 2.4 con-
       forms to the POSIX.1-2001 requirements for these signals, terminating the process with a core dump.

Next various other signals.

       Signal       Value     Action   Comment
       --------------------------------------------------------------------
       SIGIOT         6        Core    IOT trap. A synonym for SIGABRT
       SIGEMT       7,-,7      Term
       SIGSTKFLT    -,16,-     Term    Stack fault on coprocessor (unused)
       SIGIO       23,29,22    Term    I/O now possible (4.2BSD)
       SIGCLD       -,-,18     Ign     A synonym for SIGCHLD
       SIGPWR      29,30,19    Term    Power failure (System V)
       SIGINFO      29,-,-             A synonym for SIGPWR
       SIGLOST      -,-,-      Term    File lock lost
       SIGWINCH    28,28,20    Ign     Window resize signal (4.3BSD, Sun)
       SIGUNUSED    -,31,-     Term    Unused signal (will be SIGSYS)

       (Signal 29 is SIGINFO / SIGPWR on an alpha but SIGLOST on a sparc.)

       SIGEMT  is  not  specified in POSIX.1-2001, but nevertheless appears on most other Unices, where its default
       action is typically to terminate the process with a core dump.

       SIGPWR (which is not specified in POSIX.1-2001) is typically ignored by default on those other Unices  where
       it appears.

       SIGIO (which is not specified in POSIX.1-2001) is ignored by default on several other Unices.

   Real-time Signals
       Linux  supports  real-time  signals  as  originally  defined  in  the POSIX.1b real-time extensions (and now
       included in POSIX.1-2001).  Linux supports 32 real-time signals, numbered from 32 (SIGRTMIN) to  63  (SIGRT-
       MAX).   (Programs  should  always  refer  to real-time signals using notation SIGRTMIN+n, since the range of
       real-time signal numbers varies across Unices.)

       Unlike standard signals, real-time signals have no predefined meanings: the entire set of real-time  signals
       can be used for application-defined purposes.  (Note, however, that the LinuxThreads implementation uses the
       first three real-time signals.)

       The default action for an unhandled real-time signal is to terminate the receiving process.

       Real-time signals are distinguished by the following:

       1.  Multiple instances of real-time signals can be queued.  By contrast, if multiple instances of a standard
           signal are delivered while that signal is currently blocked, then only one instance is queued.

       2.  If  the  signal is sent using sigqueue(2), an accompanying value (either an integer or a pointer) can be
           sent with the signal.  If the receiving process establishes a handler for this signal using the  SA_SIG-
           INFO flag to sigaction(2) then it can obtain this data via the si_value field of the siginfo_t structure
           passed as the second argument to the handler.  Furthermore, the si_pid and si_uid fields of this  struc-
           ture can be used to obtain the PID and real user ID of the process sending the signal.

       3.  Real-time  signals are delivered in a guaranteed order.  Multiple real-time signals of the same type are
           delivered in the order they were sent.  If different real-time signals are sent to a process,  they  are
           delivered starting with the lowest-numbered signal.  (I.e., low-numbered signals have highest priority.)

       If both standard and real-time signals are pending for a process,  POSIX  leaves  it  unspecified  which  is
       delivered first.  Linux, like many other implementations, gives priority to standard signals in this case.

       According  to  POSIX, an implementation should permit at least _POSIX_SIGQUEUE_MAX (32) real-time signals to
       be queued to a process.  However, Linux does things differently.  In kernels  up  to  and  including  2.6.7,
       Linux  imposes  a system-wide limit on the number of queued real-time signals for all processes.  This limit
       can be viewed and (with privilege)  changed  via  the  /proc/sys/kernel/rtsig-max  file.   A  related  file,
       /proc/sys/kernel/rtsig-nr,  can  be  used  to  find out how many real-time signals are currently queued.  In
       Linux 2.6.8, these /proc interfaces were replaced by the RLIMIT_SIGPENDING resource limit, which specifies a
       per-user limit for queued signals; see setrlimit(2) for further details.