Editing Signal (IPC) (section)

==Sending signals==
The {{tt|[[Kill (command)|kill]](2)}} system call sends a specified signal to a specified process, if permissions allow. Similarly, the {{tt|[[kill (command)|kill(1)]]}} command allows a user to send signals to processes. The {{tt|raise(3)}} library function sends the specified signal to the current process.

[[Exception handling|Exceptions]] such as [[division by zero]], [[segmentation violation]] ([[#SIGSEGV|SIGSEGV]]), and floating point exception ([[#SIGFPE|SIGFPE]]) will cause a [[core dump]] and terminate the program.

The kernel can generate signals to notify processes of events. For example, [[#SIGPIPE|SIGPIPE]] will be generated when a process writes to a pipe which has been closed by the reader; by default, this causes the process to terminate, which is convenient when constructing [[Pipeline (Unix)|shell pipelines]].

Typing certain key combinations at the [[Computer terminal|controlling terminal]] of a running process causes the system to send it certain signals:<ref>{{cite web |title=Termination Signals |url=https://www.gnu.org/software/libc/manual/html_node/Termination-Signals.html |website=The GNU C Library)}}</ref>

* [[Control-C|Ctrl-C]] (in older Unixes, DEL) sends an INT signal ("interrupt", [[#SIGINT|SIGINT]]); by default, this causes the process to terminate.
* [[Ctrl-Z]] sends a TSTP signal ("terminal stop", [[SIGTSTP]]); by default, this causes the process to suspend execution.<ref>{{cite web |title=Job Control Signals |url=https://www.gnu.org/software/libc/manual/html_node/Job-Control-Signals.html |website=The GNU C Library}}</ref>
* [[Control-\|Ctrl-\]] sends a QUIT signal ([[#SIGQUIT|SIGQUIT]]); by default, this causes the process to terminate and dump core.
* [[Status key|Ctrl-T]] (not supported on all UNIXes) sends an INFO signal ([[#SIGINFO|SIGINFO]]); by default, and if supported by the command, this causes the operating system to show information about the running command.<ref>{{cite web |title=Miscellaneous Signals |url=https://www.gnu.org/software/libc/manual/html_node/Miscellaneous-Signals.html |website=The GNU C Library}}</ref>

These default key combinations with modern operating systems can be changed with the {{tt|[[stty]]}} command.