SIGNAL
NAME DESCRIPTION CONFORMING TO BUGS SEE ALSO
signal - list of available signals
Linux supports the signals listed below. Several signal numbers are architecture dependent. First the signals described in POSIX.1.
Signal Value Action Comment
SIGHUP 1 A Hangup detected on controlling terminal
or death of controlling process
SIGINT 2 A Interrupt from keyboard SIGQUIT 3 C Quit from keyboard SIGILL 4 C Illegal Instruction SIGABRT 6 C Abort signal from abort(3) SIGFPE 8 C Floating point exception SIGKILL 9 AEF Kill signal SIGSEGV 11 C Invalid memory reference SIGPIPE 13 A Broken pipe: write to pipe with no readers SIGALRM 14 A Timer signal from alarm(2) SIGTERM 15 A Termination signal SIGUSR1 30,10,16 A User-defined signal 1 SIGUSR2 31,12,17 A User-defined signal 2 SIGCHLD 20,17,18 B Child stopped or terminated SIGCONT 19,18,25 Continue if stopped SIGSTOP 17,19,23 DEF Stop process SIGTSTP 18,20,24 D Stop typed at tty SIGTTIN 21,21,26 D tty input for background process SIGTTOU 22,22,27 D tty output for background process
Next the signals not in POSIX.1 but described in SUSv2.
Signal Value Action Comment
SIGBUS 10,7,10 C Bus error (bad memory access) SIGPOLL A Pollable event (Sys V). Synonym of SIGIO SIGPROF 27,27,29 A Profiling timer expired SIGSYS 12,-,12 C Bad argument to routine (SVID) SIGTRAP 5 C Trace/breakpoint trap SIGURG 16,23,21 B Urgent condition on socket (4.2 BSD) SIGVTALRM 26,26,28 A Virtual alarm clock (4.2 BSD) SIGXCPU 24,24,30 C CPU time limit exceeded (4.2 BSD) SIGXFSZ 25,25,31 C File size limit exceeded (4.2 BSD)
(For the cases SIGSYS, SIGXCPU, SIGXFSZ, and on some architectures also SIGBUS, the Linux default action up to now (2.3.27) is A (terminate), while SUSv2 prescribes C (terminate and dump core).)
Next various other signals.
Signal Value Action Comment
SIGIOT 6 C IOT trap. A synonym for SIGABRT SIGEMT 7,-,7 SIGSTKFLT -,16,- A Stack fault on coprocessor SIGIO 23,29,22 A I/O now possible (4.2 BSD)
SIGCLD -,-,18 A synonym for SIGCHLD SIGPWR 29,30,19 A Power failure (System V) SIGINFO 29,-,- A synonym for SIGPWR SIGLOST -,-,- A File lock lost SIGWINCH 28,28,20 B Window resize signal (4.3 BSD, Sun) SIGUNUSED -,31,- A Unused signal (will be SIGSYS)
(Here - denotes that a signal is absent; there where three values are given, the first one is usually valid for alpha and sparc, the middle one for i386 and ppc and sh, the last one for mips. Signal 29 is SIGINFO / SIGPWR on an alpha but SIGLOST on a sparc.)
The letters in the "Action" column have the following meanings:
A Default action is to terminate the process.
B Default action is to ignore the signal.
C Default action is to terminate the process and dump core.
D Default action is to stop the process.
E Signal cannot be caught.
F Signal cannot be ignored.
POSIX.1
SIGIO and SIGLOST have the same value. The latter is commented out in the kernel source, but the build process of some software still thinks that signal 29 is SIGLOST.
kill(1), kill(2), setitimer(2)
17 pages link to signal(7):
