# csignal

***

**1. Installing a Signal Handler**

```c++
#include <csignal>

void signal_handler(int signal) {
  // Handle the signal
}

int main() {
  signal(SIGINT, signal_handler);  // Handle Ctrl+C (SIGINT)
  // ...
}
```

**2. Raising a Signal**

```c++
#include <csignal>

int main() {
  raise(SIGTERM);  // Send the SIGTERM signal to the current process
}
```

**3. Blocking a Signal**

```c++
#include <csignal>

int main() {
  sigset_t mask;  // Signal mask
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  sigprocmask(SIG_BLOCK, &mask, nullptr);
  // ...
}
```

**4. Unblocking a Signal**

```c++
#include <csignal>

int main() {
  sigset_t mask;  // Signal mask
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  sigprocmask(SIG_UNBLOCK, &mask, nullptr);  // Unblock Ctrl+C
}
```

**5. Waiting for a Signal**

```c++
#include <csignal>

int main() {
  int signal;  // Received signal number
  sigwait(&set, &signal);  // Wait for a signal in the set
  // Handle the signal using signal
}
```

**6. Sending a Signal to a Parent Process**

```c++
#include <csignal>

int main() {
  kill(getppid(), SIGUSR1);  // Send the SIGUSR1 signal to the parent process
}
```

**7. Sending a Signal to a Process Group**

```c++
#include <csignal>

int main() {
  killpg(getpgid(0), SIGTERM);  // Send the SIGTERM signal to the current process group
}
```

**8. Checking if a Signal is Pending**

```c++
#include <csignal>

int main() {
  sigset_t pending;  // Set of pending signals
  sigpending(&pending);
  if (sigismember(&pending, SIGINT)) {
    // Ctrl+C (SIGINT) is pending
  }
}
```

**9. Generating a Signal from an Async Event**

```c++
#include <csignal>
#include <unistd.h>

void signal_handler(int signal) {
  // Handle the signal
}

int main() {
  aiocb aio;  // Asynchronous I/O control block
  // ...
  aio_sigevent sigevent;
  sigevent.sigev_value.sival_ptr = &aio;
  sigevent.sigev_notify = SIGEV_SIGNAL;
  sigevent.sigev_signo = SIGIO;
  aio_setup(&aio, &sigevent, 0);
  aio_read(&aio);
  signal(SIGIO, signal_handler);  // Handle the SIGIO signal generated by the async I/O
  // ...
}
```

**10. Using a Thread-safe Signal Handler**

```c++
#include <csignal>
#include <thread>

void signal_handler(int signal) {
  // Thread-safe way to handle the signal
}

int main() {
  std::thread t(signal_handler);  // Create a thread to handle the signal
  // ...
}
```

**11. Using a Signal Queue**

```c++
#include <csignal>

void signal_handler(int signal, siginfo_t* info, void* context) {
  // Handle the signal using the queue information
}

int main() {
  sigset_t mask;
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  sigprocmask(SIG_BLOCK, &mask, nullptr);
  
  struct sigaction sa;
  memset(&sa, 0, sizeof(sa));
  sa.sa_sigaction = signal_handler;
  sa.sa_flags = SA_SIGINFO | SA_RESTART;
  sigaction(SIGINT, &sa, nullptr);  // Handle Ctrl+C using a signal queue

  while (true) {
    // Do something
    sigsuspend(&mask);  // Wait for a signal in the queue
  }
}
```

**12. Using a Timeout Signal**

```c++
#include <csignal>

void timeout_handler(int signal) {
  // Handle the timeout
}

int main() {
  struct itimerval itv;
  itv.it_value.tv_sec = 10;  // Set a 10-second timeout
  itv.it_value.tv_usec = 0;
  itv.it_interval.tv_sec = 0;  // No periodic timeout
  itv.it_interval.tv_usec = 0;
  setitimer(ITIMER_REAL, &itv, nullptr);  // Set the timeout using ITIMER_REAL
  signal(SIGALRM, timeout_handler);  // Handle the timeout signal (SIGALRM)
  // ...
}
```

**13. Using a Signal Blocker**

```c++
#include <csignal>

int main() {
  sigset_t mask;
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  block_signal(SIG_BLOCK, &mask);  // Block the signal using a signal blocker
  // ...
}
```

**14. Unblocking a Signal Using a Signal Blocker**

```c++
#include <csignal>

int main() {
  sigset_t mask;
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  block_signal(SIG_BLOCK, &mask);  // Block the signal
  // ...
  block_signal(SIG_UNBLOCK, &mask);  // Unblock the signal
}
```

**15. Sending a Signal Using a Signal Blocker**

```c++
#include <csignal>

int main() {
  pid_t pid;
  sigset_t mask;
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  block_signal(SIG_BLOCK, &mask);  // Block the signal
  pid = fork();
  if (pid) {
    // Parent process
    block_signal(SIG_UNBLOCK, &mask);  // Unblock the signal in the parent
    kill(pid, SIGINT);  // Send the SIGINT signal to the child
  } else {
    // Child process
    // ...
  }
}
```

**16. Waiting for a Signal Using a Signal Blocker**

```c++
#include <csignal>

int main() {
  sigset_t mask;
  sigemptyset(&mask);
  sigaddset(&mask, SIGINT);  // Block Ctrl+C (SIGINT)
  block_signal(SIG_BLOCK, &mask);  // Block the signal
  while (true) {
    int signal;
    wait_for_signal(&mask, &signal);  // Wait for a signal in the mask
    // Handle the signal using signal
  }
}
```

**17. Ignoring a Signal**

```c++
#include <csignal>

int main() {
  signal(SIGTERM, SIG_IGN);  // Ignore the SIGTERM signal
}
```

**18. Restricting a Signal to a Specific Thread**

```c++
#include <csignal>
#include <thread>

void signal_handler(int signal) {
  // Handle the signal in the specific thread
}

int main() {
  pthread_t thread;
  pthread_create(&thread, nullptr, signal_handler, nullptr);
  pthread_sigmask(SIG_BLOCK, &mask, nullptr);  // Block the signal in the main thread
  // ...
}
```

**19. Using a Signal Hook**

```c++
#include <csignal>

int main() {
  signal_hook<int>(SIGINT, [](int signal) {
    // Handle the SIGINT signal
  });
}
```

**20. Using a Boost.Signal**

```c++
#include <boost/signals2.hpp>

struct signal_type {
  int value;
};

boost::signals2::signal<void(const signal_type&)> signal;

int main() {
  signal.connect([](const signal_type& signal) {
    // Handle the signal
  });
  // ...
}
```

**21. Using a Qt Signal**

```c++
#include <QtCore>

class MyObject : public QObject {
  Q_OBJECT
public:
  Q_SIGNAL void mySignal(int value);
};

int main() {
  MyObject object;
  QObject::connect(&object, &MyObject::mySignal, [](int value) {
    // Handle the signal
  });
  // ...
}
```

**22. Using a Poco Signal**

```c++
#include <Poco/Signal.h>

Poco::Signal<int> signal;

int main() {
  signal.connect([](int value) {
    // Handle the signal
  });
  // ...
}
```

**23. Using a Signalslot Signal**

```c++
#include <signalslot>

class MyObject {
public:
  signalslot::signal<int> mySignal;
};

int main() {
  MyObject object;
  object.mySignal.connect([](int value) {
    // Handle the signal
  });
  // ...
}
```

**24. Using a CMake Signal**

```cmake
add_custom_command(
  TARGET my_target
  POST_BUILD
  COMMAND my_script
  DEPENDS my_source
  VERBATIM
)
```

**25. Using a Ninja Signal**

```ninja
build my_target: my_source
  command = my_script
```

**26. Using a Meson Signal**

```meson
custom_target('my_target',
  input: 'my_source',
  command: 'my_script',
  install: true)
```

**27. Generating a Signal from a Breakpoint**

```gdb
set schedule-signal SIGSTOP
```

**28. Generating a Signal from a Python Script**

```python
import signal
signal.signal(signal.SIGINT, lambda x, y: print("Ctrl+C pressed"))
```

**29. Using a Thread-safe Signal Handler in Python**

```python
import signal
import threading

def signal_handler(signal, frame):
  print("Signal received")

thread = threading.Thread(target=signal.signal, args=(signal.SIGINT, signal_handler))
thread.start()
```

**30. Using a Timeout Signal in Python**

```python
import signal
import time

def timeout_handler(signal, frame):
  print("Timeout")

signal.signal(signal.SIGALRM, timeout_handler)
signal.alarm(10)
time.sleep(15)
```

**31. Using a Signal Queue in Python**

```python
import signal
import threading

def signal_handler(signal, frame, info):
  print("Signal received", info.si_signo)

thread = threading.Thread(
  target=signal.signal, args=(signal.SIGINT, signal_handler), kwargs={'siginfo': True}
)
thread.start()
```

**32. Using a Signal Blocker in Python**

```python
import signal

def signal_handler(signal, frame):
  print("Signal received")

signal.signal(signal.SIGINT, signal_handler)
signal.siginterrupt(signal.SIGINT, False)
```

**33. Sending a Signal Using a Signal Blocker in Python**

```python
import signal
import os

def signal_handler(signal, frame):
  print("Signal received")

pid = os.fork()
if pid:
  # Parent process
  signal.siginterrupt(signal.SIGINT, False)
  os.kill(pid, signal.SIGINT)
else:
  # Child process
  signal.signal(signal.SIGINT, signal_handler)
```

**34. Waiting for a Signal Using a Signal Blocker in Python**

```python
import signal
import time

def signal_handler(signal, frame):
  print("Signal received")

signal.signal(signal.SIGINT, signal_handler)
signal.siginterrupt(signal.SIGINT, False)
while True:
  time.sleep(1)
```

**35. Ignoring a Signal in Python**

```python
import signal

signal.signal(signal.SIGINT, signal.SIG_IGN)
```

**36. Restricting a Signal to a Specific Thread in Python**

```python
import signal
import threading

def signal_handler(signal, frame):
  print("Signal received")

thread = threading.Thread(target=signal.signal, args=(signal.SIGINT, signal_handler))
thread.start()
thread.join()
```

**37. Using a Signal Hook in Python**

```python
import signal

def signal_handler(signal, frame):
  print("Signal received")

signal.signal(signal.SIGINT, signal_handler)
signal.hook_signal(signal.SIGINT)
```

**38. Using a Boost.Signal in Python**

```python
import boost

class MyObject:
  def __init__(self):
    self.signal = boost.signals2.signal<void(int)>()

    self.signal.connect(lambda value: print("Signal emitted"))

    self.signal(1)  # Emit the signal
```

**39. Using a Qt Signal in Python**

```python
from PyQt5.QtCore import pyqtSignal

class MyObject(QObject):
  mySignal = pyqtSignal(int)

    self.mySignal.connect(lambda value: print("Signal emitted"))

    self.mySignal.emit(1)  # Emit the signal
```

**40. Using a Poco Signal in Python**

```python
import poco

class MyObject:
  def __init__(self):
    self.signal = poco.Signal<int>()

    self.signal.connect(lambda value: print("Signal emitted"))

    self.signal(1)  # Emit the signal
```

**41. Using a Signalslot Signal in Python**

```python
import signalslot

class MyObject:
  def __init__(self):
    self.mySignal = signalslot.Signal()

    self.mySignal.connect(lambda: print("Signal emitted"))

    self.mySignal()  # Emit the signal
```

**42. Using a CMake Signal in Python**

```python
import cmake

target = cmake.Target("my_target")
target.add_custom_command(
  command="my_script",
  inputs="my_source",
  dependencies=target.get_dependency("my_dependency")
)
```

**43. Using a Ninja Signal in Python**

```python
import ninja

build = ninja.Build("my_target", "my_source", "my_script")
build.add_variable("dependency", "my_dependency")
```

**44. Using a Meson Signal in Python**

```python
import meson

```