signal

向右看齐 2022-08-10 06:26 152阅读 0赞

[signal][]

目录[(?)][Link 1][\[+\]][Link 1]

## 函数名: signal ##

**表头文件**\#include<signal.h>

**功 能：**设置某一信号的对应动作

**函数原型**：void (\*signal(int signum,void(\* handler)(int)))(int);

或者：typedef void(\*sig\_t) ( int );

sig\_t signal(int signum,sig\_t handler);

**参数说明**：

第一个参数signum指明了所要处理的信号类型，它可以取除了SIGKILL和SIGSTOP外的任何一种信号。

第二个参数handler描述了与信号关联的动作，它可以取以下三种值：

（1）一个无返回值的函数地址

此函数必须在signal()被调用前申明，handler中为这个函数的名字。当接收到一个类型为sig的信号时，就执行handler 所指定的函数。这个函数应有如下形式的定义：

void func(int sig);

sig是传递给它的唯一参数。执行了signal()调用后，进程只要接收到类型为sig的信号，不管其正在执行程序的哪一部分，就立即执行func()函数。当func()函数执行结束后，控制权返回进程被中断的那一点继续执行。

（2）SIG\_IGN

这个符号表示忽略该信号，执行了相应的signal()调用后，进程会忽略类型为sig的信号。

（3）SIG\_DFL

这个符号表示恢复系统对信号的默认处理。

**函数说明**：

signal()会依参数signum 指定的信号编号来设置该信号的处理函数。当指定的信号到达时就会跳转到参数handler指定的函数执行。当一个信号的信号处理函数执行时，如果进程又接收到了该信号，该信号会自动被储存而不会中断信号处理函数的执行，直到信号处理函数执行完毕再重新调用相应的处理函数。但是如果在信号处理函数执行时进程收到了其它类型的信号，该函数的执行就会被中断。

**返回值：**返回先前的信号处理 [函数指针][Link 2]，如果有错误则返回SIG\_ERR(-1)。

下面的情况可以产生Signal：

1.  按下CTRL+C产生SIGINT
2.  [硬件中断][Link 3]，如除0，非法内存访问（SIGSEV）等等
3.  Kill函数可以对进程发送Signal
4.  Kill命令。实际上是对Kill函数的一个包装
5.  [软件][Link 4]中断。如当Alarm Clock超时（SIGURG），当Reader中止之后又向管道写数据（SIGPIPE），等等

程序例:

/\* This example installs a signal handler routine for SIGFPE,

catches an integer overflow condition, makes an adjustment

to AX register, and returns. This example program MAY cause

your computer to crash, and will produce runtime errors

depending on which memory model is used.

\*/

\#pragma inline

\#include <stdio.h>

\#include <signal.h>

void Catcher(int sig, int type, int \*reglist)

printf("Caught it!\\n");

\*(reglist + 8) = 3; /\* make return AX = 3 \*/

int main(void)

signal(SIGFPE, Catcher);

asm mov ax,07FFFH /\* AX = 32767 \*/

asm inc ax /\* cause overflow \*/

asm into /\* activate handler \*/

/\* The handler set AX to 3 on return. If that hadn't happened,

there would have been another exception when the next 'into'

was executed after the 'dec' instruction. \*/

asm dec ax /\* no overflow now \*/

asm into /\* doesn't activate \*/

return 0;

2 Signals:

<table style="border-collapse:collapse; border-spacing:0px; margin:5px 0px; word-wrap:break-word; word-break:break-all; font-size:12px; line-height:22px; color:rgb(0,0,0); border-right-width:1px; border-right-style:solid; border-right-color:rgb(220,222,224); border-left-width:1px; border-left-style:solid; border-left-color:rgb(220,222,224); font-family:arial,宋体,sans-serif"> 
 <tbody> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px"> 
     <strong>Signal</strong> 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px"> 
     <strong>Description</strong> 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGABRT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      由调用abort函数产生，进程非正常退出 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGALRM 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      用alarm函数设置的timer超时或setitimer函数设置的interval timer超时 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGBUS 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      某种特定的硬件异常，通常由内存访问引起 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGCANCEL 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      由Solaris Thread Library内部使用，通常不会使用 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGCHLD 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      进程Terminate或Stop的时候，SIGCHLD会发送给它的父进程。缺省情况下该Signal会被忽略 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGCONT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当被stop的进程恢复运行的时候，自动发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGEMT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      和实现相关的硬件异常 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGFPE 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      数学相关的异常，如被0除，浮点溢出，等等 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGFREEZE 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Solaris专用，Hiberate或者Suspended时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGHUP 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      发送给具有Terminal的Controlling Process，当terminal被disconnect时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGILL 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      非法指令异常 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGINFO 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      BSD signal。由Status Key产生，通常是CTRL+T。发送给所有Foreground Group的进程 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGINT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      由Interrupt Key产生，通常是CTRL+C或者DELETE。发送给所有ForeGround Group的进程 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGIO 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      异步IO事件 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGIOT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      实现相关的硬件异常，一般对应SIGABRT 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGKILL 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      无法处理和忽略。中止某个进程 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGLWP 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      由Solaris Thread Libray内部使用 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGPIPE 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      在reader中止之后写Pipe的时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGPOLL 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当某个事件发送给Pollable Device的时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGPROF 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Setitimer指定的Profiling Interval Timer所产生 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGPWR 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      和系统相关。和UPS相关。 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGQUIT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      输入Quit Key的时候（CTRL+\）发送给所有Foreground Group的进程 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGSEGV 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      非法内存访问 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGSTKFLT 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Linux专用，数学协处理器的栈异常 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGSTOP 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      中止进程。无法处理和忽略。 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGSYS 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      非法系统调用 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGTERM 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      请求中止进程，kill命令缺省发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGTHAW 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Solaris专用，从Suspend恢复时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGTRAP 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      实现相关的硬件异常。一般是调试异常 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGTSTP 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Suspend Key，一般是Ctrl+Z。发送给所有Foreground Group的进程 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGTTIN 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当Background Group的进程尝试读取Terminal的时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGTTOU 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当Background Group的进程尝试写Terminal的时候发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGURG 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当out-of-band data接收的时候可能发送 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGUSR1 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      用户自定义signal 1 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGUSR2 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      用户自定义signal 2 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGVTALRM 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      setitimer函数设置的Virtual Interval Timer超时的时候 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGWAITING 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Solaris Thread Library内部实现专用 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGWINCH 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当Terminal的窗口大小改变的时候，发送给Foreground Group的所有进程 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGXCPU 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      当CPU时间限制超时的时候 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGXFSZ 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      进程超过文件大小限制 
    </div> </td> 
  </tr> 
  <tr> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      SIGXRES 
    </div> </td> 
   <td align="left" style="margin:0px; padding:2px 10px; height:12px; border:1px solid rgb(220,222,224)"> 
    <div style="margin-bottom:0px">
      Solaris专用，进程超过资源限制的时候发送 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

## [编辑本段][Link 5]注意点 ##

1、不要使用低级的或者STDIO.H的IO函数

2、不要使用对操作

3、不要进行 [系统调用][Link 6]

4、不是浮点信号的时候不要用 **longjmp**

5、signal函数是由ISO C定义的。因为ISO C不涉及 [多进程][Link 7]， [进程组][Link 8]以及终端I/O等，所以他对信号的定义非常含糊，以至于对UNIX系统而言几乎毫无用处。

备注：因为signal的语义与现实有关，所以最好使用sigaction函数替代本函数。

[signal]: http://www.csdn.net/tag/signal
[Link 1]: http://blog.csdn.net/cqkxboy168/article/details/10904031#
[Link 2]: http://baike.baidu.com/view/1604730.htm
[Link 3]: http://baike.baidu.com/view/486976.htm
[Link 4]: http://baike.baidu.com/view/37.htm
[Link 5]: http://baike.baidu.com/link?url=NX44tgTjHfF2-kcRV_iRy-KRuEZhzB_S3db9m9uZCeYzidrJqQfkL7-HgQsGsT2Y#
[Link 6]: http://baike.baidu.com/view/47173.htm
[Link 7]: http://baike.baidu.com/view/549647.htm
[Link 8]: http://baike.baidu.com/view/1545127.htm