C signal handling

In the C Standard Library, signal processing defines how a program handles various signals while it executes. A signal can report some exceptional behavior within the program, or a signal can report some asynchronous event outside the program.

Standard signals

The C standard defines only 6 signals. They are all defined in header :

SIGABRT – "abort", abnormal termination.
SIGFPE – floating point exception.
SIGILL – "illegal", invalid instruction.
SIGINT – "interrupt", interactive attention request sent to the program.
SIGSEGV – "segmentation violation", invalid memory access.
SIGTERM – "terminate", termination request sent to the program.

Additional signals may be specified in the header by the implementation. For example, Unix and Unix-like operating systems define more than 15 additional signals; see Unix signal.

Debugging

SIGTRAP for debugging purposes. It is platform-dependent and may be used on Unix-like operating systems.

Handling

A signal can be generated by calling raise or kill system calls. raise sends a signal to the current process, kill sends a signal to a specific process.
A signal handler is a function which is called by the target environment when the corresponding signal occurs. The target environment suspends execution of the program until the signal handler returns or calls longjmp.
Signal handlers can be set with signal or sigaction. The behavior of signal has been changed multiple times across history and its use is discouraged. It is only portable when used to set a signal's disposition to SIG_DFL or SIG_IGN. Signal handlers can be specified for all but two signals.
If the signal reports an error within the program, the signal handler can terminate by calling abort, exit, or longjmp.

Functions

Function	Description
	artificially sends a signal to the calling process
`kill`	artificially sends a signal to a specified process
	sets the action taken when the program receives a specific signal

Example usage

include
include
include

volatile sig_atomic_t status = 0;
static void catch_function
int main

Other languages

C++

C signals are traditionally used the same way in C++ as in C. However, one can also write wrappers for RAII-style usage.

export module org.wikipedia.example;
import ; // necessary to obtain macros
import std;
using std::function;
export namespace org::wikipedia::example

This can also be done with Boost, using the class boost::asio::signal_set.

C#

C signals can be used with P/Invoke and Mono.Unix.Native.Syscall.

Java

C signals are unofficially usable in Java language, from module jdk.unsupported, with internal JVM classes sun.misc.Signal and interface sun.misc.SignalHandler.

package org.wikipedia.example;
import sun.misc.Signal;
import sun.misc.SignalHandler;
public class Example

Rust

Signals can be used with the signal_hook crate in Rust.

use std::process;
use std::thread;
use std::time::Duration;
use signal_hook::consts::signal::*;
use signal_hook::iterator::Signals;
fn main