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-*- mode: outline; coding: utf-8 -*-
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* Send signal to process.
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$ kill -s NAME PID
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Under C you can use kill(2) system call which will send the specified signal
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to the process, if permissions allow, or raise(3) library function, which
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sends the specified signal to the current process.
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* List of signals.
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$ kill --list
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$ kill -l # short variant
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See
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http://en.wikipedia.org/wiki/Unix_signals
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** SIGHUP 1.
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Hangup. Type: notification, can be handled.
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Sent when assigned to process terminal closed.
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nohup(1) utility used as a wrapper to start a program and make it immune to
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SIGHUP.
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The default action on POSIX-compliant systems is an abnormal termination.
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Demon used this signal as commant to reread config file.
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** SIGINT 2
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Interrupt. Ctrl-C. Type: control, can be handled.
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Signal sent to a process by its controlling terminal when a user wishes to
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interrupt the process.
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By default, this causes the process to terminate.
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** SIGQUIT 3.
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Quit. Ctrl-\. Type: control.
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Signal sent to a process by its controlling terminal when the user requests
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that the process dump core.
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By default, this causes the process to terminate and produce a memory core dump.
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** SIGILL 4.
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Illegal instruction. Type: exception, can not be handled.
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Signal sent to a process when it attempts to execute a malformed, unknown, or
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privileged instruction.
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** SIGTRAP 5.
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Trace trap. Type: debug, can be handled.
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Signal sent to a process when a condition arises that a debugger has requested
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to be informed of.
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By default this causes abnormal termination of the process.
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** SIGABRT 6.
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Type: control, can be handled.
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Signal sent to a computer program to tell it to abort, ie terminate.
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SIGABRT is sent by the process to itself when it calls the abort libc
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function. It is used when an assertion fails.
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By default this causes abnormal termination of the process.
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** SIGEMT 7.
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Emt instruction.
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** SIGFPE 8.
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Floating point exception. Type: exception, can be handled.
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Signal sent to a process when it performs an erroneous arithmetic operation
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(like division by zero).
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By default cause a core dump and a program exit.
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** SIGKILL 9.
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Kill. Type: control, can not be handled.
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Signal sent to a process to cause it to terminate immediately.
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Zombie processes cannot be killed since they are already dead and waiting for
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their parent processes to reap them.
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Processes that are in the blocked state will not die until they wake up again.
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** SIGBUS 10.
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Bus error. Type: exception, can not be handled.
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Signal sent to a process when it causes a bus error.
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By default this causes abnormal termination of the process.
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** SIGSEGV 11.
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Segmentation violation. Type: exception.
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Signal sent to a process when it makes an invalid memory reference, or
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segmentation fault.
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By default cause a core dump and a program exit.
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** SIGSYS 12.
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Bad argument to system call. Type: exception.
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By default this causes abnormal termination of the process.
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** SIGPIPE 13.
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Write on a pipe with no one to read it. Type: notification.
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Signal sent to a process when it attempts to write to a pipe without a process
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connected to the other end.
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This causes the process to terminate, which is convenient when constructing
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shell pipelines.
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** SIGALRM 14.
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Alarm clock. Type: notification.
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Signal sent to a process when a time limit has elapsed.
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By default this causes abnormal termination of the process.
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** SIGTERM 15.
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Software termination signal. Type: control.
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Signal sent to a process to request its termination.
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It causes the termination of a process, but unlike the SIGKILL signal, it can
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be caught and interpreted (or ignored) by the process.
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SIGTERM is akin to asking a process to terminate nicely, allowing cleanup and
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closure of files. For this reason, on many Unix systems during shutdown, init
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issues SIGTERM to all processes that are not essential to powering off, waits
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a few seconds, and then issues SIGKILL to forcibly terminate any such
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processes that remain.
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By default kill(1) send to process SIGTERM signal.
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** SIGURG 16.
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Urgent condition on IO channel. Type: notification.
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By default this signal ignored.
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** SIGSTOP 17.
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Signal sent to a process to stop it for later resumption. Type: control.
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SIGSTOP cannot be caught or ignored.
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Usually SIGSTOP and SIGCONT are used for job control in the Unix shell.
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** SIGTSTP 18.
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Stop signal from tty. Ctrl-Z. Type: control.
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By default, this causes the process to suspend execution.
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** SIGCONT 19.
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Continue a stopped process. Type: control.
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Signal sent to restart a process previously paused by the SIGSTOP or SIGTSTP
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signal.
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** SIGCHLD 20.
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To parent on child stop or exit. Type: notification.
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By default the signal is simply ignored. In C:
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signal(SIGCHLD, SIG_IGN);
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Parent can invoke wait(1) otherwise children stay zombie.
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** SIGTTIN 21.
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Signal sent to a process when it attempts to read from the tty while in the
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background.
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Daemons do not have controlling terminals and should never receive this
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signal.
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By default this causes suspends of the process.
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** SIGTTOU 22.
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Signal sent to a process when it attempts to write to the tty while in the
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background.
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Daemons do not have controlling terminals and should never receive this
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signal.
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By default this causes suspends of the process.
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** SIGPOLL 23.
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System V name for SIGIO. Type: notification.
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Signal sent to a process when an asynchronous I/O event occurs.
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By default this causes abnormal termination of the process.
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** SIGXCPU 24.
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Exceeded CPU time limit. Type: notification.
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By default this causes abnormal termination of the process.
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** SIGXFSZ 25.
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Exceeded file size limit as determined by the ulimit system call and shell
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builtin. Type: notification.
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By default this causes abnormal termination of the process.
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** SIGVTALRM 26.
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Virtual time alarm. Type: notification.
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Signal sent to a process when a time limit has elapsed.
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By default this causes abnormal termination of the process.
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** SIGPROF 27.
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Profiling time alarm. Type: debug.
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Signal sent to a process when the profiling timer expires.
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By default this causes abnormal termination of the process.
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** SIGWINCH 28.
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Window changed. Type: notification.
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Signal sent to a process when its controlling terminal changes size.
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By default this signal ignored.
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** SIGLOST 29.
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Signal sent to process when a file lock is lost. This may occur, for example,
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when an NFS server reboots and forgets about a file lock.
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By default this causes abnormal termination of the process.
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** SIGUSR1 30.
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User defined signal 1. Type: user defined.
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By default this causes abnormal termination of the process.
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** SIGUSR2 31.
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User defined signal 2. Type: user defined.
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By default this causes abnormal termination of the process.
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