C库函数 void (*signal(int sig, void (*func)(int)))(int)设置一个函数来处理信号，即信号数量sig的信号处理程序 。

声明

以下是signal()函数的声明。

void (*signal(int sig, void (*func)(int)))(int)

参数

• sig -- 这是信号的处理功能被设置的号码。以下是几个重要的标准信号的数字：

macro	signal
SIGABRT	(Signal Abort) Abnormal termination, such as is initiated by the function.
SIGFPE	(Signal Floating-Yiibai Exception) Erroneous arithmetic operation, such as zero divide or an operation resulting in overflow (not necessarily with a floating-yiibai operation).
SIGILL	(Signal Illegal Instruction) Invalid function image, such as an illegal instruction. This is generally due to a corruption in the code or to an attempt to execute data.
SIGINT	(Signal Interrupt) Interactive attention signal. Generally generated by the application user.
SIGSEGV	(Signal Segmentation Violation) Invalid access to storage: When a program tries to read or write outside the memory it is allocated for it.
SIGTERM	(Signal Terminate) Termination request sent to program.

• func -- 这是一个指向函数的指针。这可以是由程序员或一个以下预定义的函数的定义的函数：

SIG_DFL	默认处理：对于某一特定信号，该信号处理的默认操作。
SIG_IGN	忽略信号：信号被忽略。

返回值

这个函数返回前一个信号处理程序或错误SIG_ERR的值。

例子

下面的例子显示了signal()函数的用法。

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>

void sighandler(int);

int main()
{
   signal(SIGINT, sighandler);

   while(1) 
   {
      printf("Going to sleep for a second...
");
      sleep(1);
   }

   return(0);
}

void sighandler(int signum)
{
   printf("Caught signal %d, coming out...
", signum);
   exit(1);
}

让我们编译和运行上面的程序，这将产生以下结果，程序将无限循环中去。跳出程序使用Ctrl + C键。

Going to sleep for a second...
Going to sleep for a second...
Going to sleep for a second...
Going to sleep for a second...
Going to sleep for a second...
Caught signal 2, coming out...