=====signal=====
Syntax:

<code>
    #include <csignal>
    void ( *signal( int signal, void (* func) (int)) ) (int);
</code>

The signal() function sets func to be called when signal is received by your
program. func can be a custom signal handler, or one of these macros (defined
in the csignal header file):

^Macro^Explanation^
|SIG_DFL|default signal handling|
|SIG_IGN|ignore the signal|

Some basic signals that you can attach a signal handler to are:

^Signal^Description^
|SIGTERM|Generic stop signal that can be caught.|
|SIGINT|Interrupt program, normally ctrl-c.|
|SIGQUIT|Interrupt program, similar to SIGINT.|
|SIGKILL|Stops the program. Cannot be caught.|
|SIGHUP|Reports a disconnected terminal.|

The return value of signal() is the address of the previously defined function
for this signal, or SIG_ERR if there is an error.

For example, the following example uses the signal() function to call an arbitrary number of
functions when the user aborts the program. The functions are stored in a
vector, and a single "clean-up" function calls each function in that vector of
functions when the program is aborted:

<code>
  void f1() {
    cout << "calling f1()..." << endl;
  }

  void f2() {
    cout << "calling f2()..." << endl;
  }

  typedef void(*endFunc)(void);
  vector<endFunc> endFuncs;

  void cleanUp( int dummy ) {
    for( unsigned int i = 0; i < endFuncs.size(); i++ ) {
      endFunc f = endFuncs.at(i);
      (*f)();
    }
    exit(-1);
  }

  int main() {

    // connect various signals to our clean-up function
    signal( SIGTERM, cleanUp );
    signal( SIGINT, cleanUp );
    signal( SIGQUIT, cleanUp );
    signal( SIGHUP, cleanUp );

    // add two specific clean-up functions to a list of functions
    endFuncs.push_back( f1 );
    endFuncs.push_back( f2 );

    // loop until the user breaks
    while( 1 );

    return 0;
  }
</code>

Related Topics: [[raise]]