Common Unix Signals

Name	Number	Default Action	Semantics
SIGHUP	1	Terminate	Hangup detected on controlling terminal or death of controlling process
SIGINT	2	Terminate	Interrupt from keyboard. Usually terminate the process. Can be triggered by Ctrl-C
SIGQUIT	3	Core dump	Quit from keyboard. Usually causes the process to terminate and dump core. Cab be triggered by Ctrl-\
SIGILL	4	Core dump	The process has executed an illegal hardware instruction.
SIGTRAP	5	Core dump	Trace/breakpoint trap. Hardware fault.
SIGABRT	6	Core dump	Abort signal from abort(3)
SIGFPE	8	Core dump	Floating point exception such as dividing by zero or a floating point overflow.
SIGKILL	9	Terminate	Sure way to terminate (kill) a process. Cannot be caught or ignored.
SIGSEGV	11	Core dump	The process attempted to access an invalid memory reference.
SIGPIPE	13	Terminate	Broken pipe: Sent to a process writing to a pipe or a socket with no reader (most likely the reader has terminated).
SIGALRM	14	Terminate	Timer signal from alarm(2)
SIGTERM	15	Terminate	Termination signal. The kill command send this signal by default, when no explicit signal type is provided.
SIGUSR1	30,10,16	Terminate	First user-defined signal, designed to be used by application programs which can freely define its semantics.
SIGUSR2	31,12,17	Terminate	Second user-defined signal, designed to be used by application programs which can freely define its semantics.
SIGCHLD	20,17,18	Ignore	Child stopped or terminated
SIGCONT	19,18,25	Continue / Ignore	Continue if stopped
SIGSTOP	17,19,23	Stop	Sure way to stop a process: cannot be caught or ignored. Used for non interactive job-control while SIGSTP is the interactive stop signal.
SIGTSTP	18,20,24	Stop	Interactive signal used to suspend process execution. Usually generated by typing Ctrl-Z in a terminal.
SIGTTIN	21,21,26	Stop	A background process attempt to read from its controlling terminal (tty input).
SIGTTOU	22,22,27	Stop	A background process attempt to write to its controlling terminal (tty output).
SIGIO	23,29,22	Terminate	Asynchronous I/O now event.
SIGBUS	10,7,10	Core dump	Bus error (bad memory access)
SIGPOLL		Terminate	Signals an event on a pollable device.
SIGPROF	27,27,29	Terminate	Expiration of a profiling timer set with setitimer.
SIGSYS	12,-,12	Core dump	Invalid system call. The Kernel interpreted a processor instruction as a system call, but its argument is invalid.
SIGURG	16,23,21	Ignore	Urgent condition on socket (e.g. out-of-band data).
SIGVTALRM	26,26,28	Terminate	Expiration of a virtual interval timer set with setitimer.
SIGXCPU	24,24,30	Core dump	CPU soft time limit exceeded (Resource limits).
SIGXFSZ	25,25,31	Core dump	File soft size limit exceeded (Resource limits).
SIGWINCH	28,28,20	Ignore	Informs a process of a change in associated terminal window size.

*) example command:     [ kill -9 3010 ]

*) Few unix system calls:

 *  System calls for low level file I/O

          o creat(name, permissions)

          o open(name, mode)

          o close(fd)

          o unlink(fd)

          o read(fd, buffer, n_to_read)

          o write(fd, buffer, n_to_write)

          o lseek(fd, offest, whence)

    * System Calls for process control

          o fork()

          o wait()

          o execl(), execlp(), execv(), execvp()

          o exit()

          o signal(sig, handler)

          o kill(sig, pid)

    * System Calls for IPC

          o pipe(fildes)

          o dup(fd)