signal notes

1. code example

#include <signal.h>

static void my_signal_handler(int sig)
{
    printf("receive signal %d", sig);
}

int main(/*int argc, char **argv*/) {
    struct sigaction sa;
   /* Set up the signal handler */
    sa.sa_handler = my_signal_handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_ONESHOT;
   /* 攔截Ctl+C 及 kill */
    if (sigaction(SIGINT , &sa, NULL) == -1) {
        return 1;
    }
    if (sigaction(SIGTERM , &sa, NULL) == -1) {
        return 1;
    }
}

2 常見 signal id

#define SIGINT 2 /* Interrupt (ANSI). */ 按 Ctl + C

#define SIGQUIT 3 /* Quit (POSIX). */

#define SIGILL 4 /* Illegal instruction (ANSI). */

#define SIGTRAP 5 /* Trace trap (POSIX). */

#define SIGABRT 6 /* Abort (ANSI). */

#define SIGIOT 6 /* IOT trap (4.2 BSD). */

#define SIGBUS 7 /* BUS error (4.2 BSD). */

#define SIGFPE 8 /* Floating-point exception (ANSI). */

#define SIGKILL 9 /* Kill, unblockable (POSIX). */  不可用

#define SIGUSR1 10 /* User-defined signal 1 (POSIX). */

#define SIGSEGV 11 /* Segmentation violation (ANSI). */

#define SIGUSR2 12 /* User-defined signal 2 (POSIX). */

#define SIGPIPE 13 /* Broken pipe (POSIX). */

#define SIGALRM 14 /* Alarm clock (POSIX). */

#define SIGTERM 15 /* Termination (ANSI). */ kill <process id>

#define SIGSTKFLT 16 /* Stack fault. */

#define SIGCLD SIGCHLD /* Same as SIGCHLD (System V). */

#define SIGCHLD 17 /* Child status has changed (POSIX). */

#define SIGCONT 18 /* Continue (POSIX). */

#define SIGSTOP 19 /* Stop, unblockable (POSIX). */ 不可用

3. sa.sa_flags

  
  

   
   

    
    
     
     SA_NOCLDSTOP
    
    
    
    

     
     If
     
     signumis
     
     SIGCHLD, do not receive notification when child processes stop (i.e., when childprocesses receive one of
     
     SIGSTOP, 
     
     SIGTSTP, 
     
     SIGTTINor
     
     SIGTTOU).
    
    
    
    
     
     SA_ONESHOT or 
     
     SA_RESETHAND
    
    
    
    

     
     Restore the signal action to the default state once the signal handlerhas been called.
    
    
    
    
     
     SA_ONSTACK
    
    
    
    

     
     Call the signal handler on an alternate signal stack provided by 
     
     sigaltstack(2).If an alternate stack is not available, the default stack will be used.
    
    
    
    
     
     SA_RESTART
    
    
    
    

     
     Provide behaviour compatible with BSD signal semantics by making certainsystem calls restartable across signals.
    
    
    
    
     
     SA_NOMASK or 
     
     SA_NODEFER
    
    
    
    

     
     Do not prevent the signal from being received from within its own signalhandler.
    
    
    
    
     
     SA_SIGINFO
    
    
    
    

     
     The signal handler takes 3 arguments, not one.  In this case,
     
     sa_sigactionshould be set instead of
     
     sa_handler.(The sa_sigaction field was added in Linux 2.1.86.)
    
    
   
   
  
  
 
 

4. 若是攔截 Ctrl+c 或kill, process 將無法被外部結束. 記得要自己叫exit(0)