转自 http://blog.csdn.net/elbort/article/details/7594772
sigprocmask函数：
功能描述：
设定对信号屏蔽集内的信号的处理方式(阻塞或不阻塞)。
用法：
#include <signal.h>
int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
NOTE： If oldset is non-null, the previous value of the signal mask is stored in oldset.
参数：
how：用于指定信号修改的方式，可能选择有三种
SIG_BLOCK //加入信号到进程屏蔽。
SIG_UNBLOCK //从进程屏蔽里将信号删除。
SIG_SETMASK //将set的值设定为新的进程屏蔽。
相应函数命令：
sigset_t set
sigemptyset(&set) :清空阻塞信号集合变量
sigfillset(&set) ：添加所有的信号到阻塞集合变量里
sigaddset(&set,SIGINT):添加单一信号到阻塞信号集合变量
sigdelset(&set,SIGINT):从阻塞信号集合变量中删除单一信号
sigismember(&set，int signum)：这个函数测试信号signum是否包含在信号集合set中，如果包含返回1，不包含返回0，出错返回-1。错误代码也只有一个EINVAL，表示signum不是有效的信号代码。
代码说明：最简单的一个例子
#include <stdio.h>
#include <signal.h>
int main()
{
sigset_t set; //定义阻塞信号集的变量
sigemptyset(&set); //清空变量set的阻塞信号
sigaddset(&set,SIGINT); //添加将要阻塞的信号"SIGINT"到阻塞信号集变量
sigdelset(&set,SIGINT); //从已有的阻塞信号集变量中删除阻塞信号"SIGINT"
sigaddset(&set,SIGQUIT); //添加将要阻塞的信号"SIGQUIT"到阻塞信号集变量
sigprocmask(SIG_SETMASK,&set,NULL);// 将当前的阻塞信号集合变量set设置为该进程信号阻塞列表
while(1); //
return 0;
}
结果显示：
[[email protected] test1]$ ./test
^\^\
^C
[[email protected] test1]$
说明： ^\ 键盘上是ctrl + \ 对应信号 SIGQUIT
^c 键盘上是ctrl + c 对应信号 SIGINT
该结果说明test进程屏蔽了信号SIGQUIT，没有屏蔽信号SIGINT。
sigpending 函数:
功能：返回在阻塞期间接收到阻塞信号的集合。
代码说明：
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
int main( void )
{
sigset_t set, oset, pset;
sigemptyset( &set );
sigaddset( &set, SIGINT );
sigaddset(&set,SIGQUIT);
sigaddset(&set,SIGABRT);
sigprocmask( SIG_BLOCK, &set, &oset );
printf( "Old set was %8.8ld.\n", oset );
printf( "set is %8.8ld.\n", set );
sigpending( &pset );
printf( "Pending set is %8.8ld.\n", pset );
kill( getpid(), SIGINT );
sigpending( &pset );
printf( "Pending set is %8.8ld.\n", pset );
kill( getpid(), SIGQUIT );
sigpending( &pset );
printf( "Pending set is %8.8ld.\n", pset );
kill( getpid(), SIGABRT );
sigpending( &pset );
printf( "Pending set is %8.8ld.\n", pset );
// sigprocmask( SIG_UNBLOCK, &set, &oset );
if(sigismember(&pset,SIGINT) == 1)
{
printf("SIGINT was came.\n");
}
if(sigismember(&pset,SIGQUIT) == 1)
{
printf("SIGQUIT was came.\n");
}
if(sigismember(&pset,SIGABRT) == 1)
{
printf("SIGABRT was came.\n");
}
/* The program terminates with a SIGINT */
return( EXIT_SUCCESS );
}
运行结果：
[[email protected] test1]$ ./test2
Old set was 00000000.
set is 00000038.
Pending set is 00000000.
Pending set is 00000002.
Pending set is 00000006.
Pending set is 00000038.
SIGINT was came.
SIGQUIT was came.
SIGABRT was came.
[[email protected] test1]$
注意：红色那句去掉//会得到完全不同的结果。为什么？？
//测试后，发现真的是
SIGINT was came.
SIGQUIT was came.
SIGABRT was came. 这三句话没有打印出来，不太好理解啊，sigprocmask( SIG_UNBLOCK, &set, &oset );这句话是去掉进程的信号屏蔽set，那么sigismember(&pset,SIGINT)这句&pset的信号屏蔽也是空？因为是针对相同的进程？暂且只能这么解释了.
sigsuspend函数
功能：它有一套属于自己的屏蔽信号mask，能够选择性接收某些信号。在接收到可行信号(也即是没有被屏蔽的信号)之前，运行到它时，它会一直悬挂着，有点类似pause（）函数。接受到可行信号后，它会退出悬挂并执行相应的信号函数。接收到的信号源：1.之前运行sigprocmask（）函数中阻塞的信号；2.悬挂后接受到的信号。
代码说明：
Example:sigsuspend (Correct Way to Wait for Single Signal)
sigset_tmaskall, maskmost, maskold;
intsignum = SIGUSR1;
sigfillset(&maskall);
sigfillset(&maskmost);
sigdelset(&maskmost,signum);
sigprocmask(SIG_SETMASK,&maskall, &maskold);
sigsuspend(&maskmost);
sigprocmask(SIG_SETMASK,&maskold, NULL);
sigsuspend的整个原子操作过程为：
(1) 设置新的mask阻塞当前进程；
(2) 收到信号，恢复原先mask；
(3) 调用该进程设置的信号处理函数；
(4) 待信号处理函数返回后，sigsuspend返回。
具体例子说明：
#include <stdio.h>
#include <signal.h>
#include "unistd.h"
void fun_int()
{
printf("\nsigsuspend catch SIGINT\n");
printf("The sigsuspend already restore the old mask for sigprocmask.Now still in the signal handle,next will sleep 5 seconds you can press ctrl-c to test\n");
sleep(5);
return;
}
int main()
{
sigset_t set;
sigfillset(&set);
signal(SIGINT,fun_int);
sigprocmask(SIG_SETMASK,&set,NULL);
sigdelset(&set,SIGINT);
printf("Here is the sigprocmask signal block,before use sigsuspend\n");
sleep(5);
printf("\nsleep over,next is sigsuspend\n");
sigsuspend(&set);
printf("\nI have return from the handler.I will sleep 5 seconds You can press ctrl-c to send sigint to test the mask of SIGINT restore from sigsuspend for sigprocmask\n");
sleep(10);
printf("\nTest finish\n");
return 0;
}
结果显示：
1.sigsuspend 接收信号来源为sigprocmask() block期间接收到的信号
[[email protected] test1]$ ./test
Here is the sigprocmask signal block,before use sigsuspend
^\^\^\
^C^C^C
sleep over,next is sigsuspend
sigsuspend catch SIGINT
The sigsuspend already restore the old mask for sigprocmask.Now still in the signal handle,next will sleep 5 seconds you can press ctrl-c to test
^C^C^C
I have return from the handler.I will sleep 5 seconds You can press ctrl-c to send sigint to test the mask of SIGINT restore from sigsuspend for sigprocmask
^C^C^C^\^\^\
Test finish
[[email protected] test1]$
2.sigsuspend 接收信号来源为线程进入悬挂后接收的信号
[[email protected] test1]$ ./test
Here is the sigprocmask signal block,before use sigsuspend
^\^\^\^\^\
sleep over,next is sigsuspend
^\^\^\^\^\
^C
sigsuspend catch SIGINT
The sigsuspend already restore the old mask for sigprocmask.Now still in the signal handle,next will sleep 5 seconds you can press ctrl-c to test
^C^C^C^C^C
I have return from the handler.I will sleep 5 seconds You can press ctrl-c to send sigint to test the mask of SIGINT restore from sigsuspend for sigprocmask
^C^C^C^C^C^\^\^\
Test finish
[[email protected] test1]$