UNIX环境高级编程学习之第十章信号-用信号实现父子进程同步
[code lang=”cpp”]/* FileName:ParentAndChildProcessSynchronous.c
Date: 20100309
Description: 用信号实现父子进程同步。
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
static volatile sig_atomic_t sigflag;
static sigset_t newmask, oldmask, zeromask;
static void sig_usr(int signo)
{
sigflag = 1;
}
void TELL_WAIT(void)
{
if (signal(SIGUSR1, sig_usr) == SIG_ERR)
{
printf("signal(SIGUSR1) ERROR /n");
exit(-1);
}
if (signal(SIGUSR2, sig_usr) == SIG_ERR)
{
printf("signal(SIGUSR2) ERROR /n");
exit(-1);
}
sigemptyset(&zeromask);
sigemptyset(&newmask);
sigaddset(&newmask, SIGUSR1);
sigaddset(&newmask, SIGUSR2);
if (sigprocmask(SIG_BLOCK, &newmask, &oldmask) < 0)
{
printf("SIB_BLOCK ERROR /n");
exit(-1);
}
}
void TELL_PARENT(pid_t pid)
{
kill(pid, SIGUSR2);
}
void WAIT_PARENT(void)
{
while (sigflag == 0)
{
sigsuspend(&zeromask);
}
sigflag = 0;
if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
{
printf("SIG_SETMASK ERROR/n");
exit(-1);
}
}
void TELL_CHILD(pid_t pid)
{
kill(pid, SIGUSR1);
}
void WAIT_CHILD(void)
{
while (sigflag == 0)
{
sigsuspend(&zeromask);
}
sigflag = 0;
if (sigprocmask(SIG_SETMASK, &oldmask, NULL) < 0)
{
printf("SIG_SETMASK ERROR/n");
exit(-1);
}
}
static void charatatime(char* );
int main(int argc, char* argv[])
{
pid_t pid;
TELL_WAIT();
if ((pid = fork()) < 0)
{
printf("fork error/n");
exit(-1);
}else if (pid == 0){
WAIT_PARENT();
charatatime("output from child/n");
}else{
charatatime("output from parent/n");
TELL_CHILD(pid);
}
return 0;
}
static void charatatime(char* str)
{
char* ptr;
int c;
setbuf(stdout, NULL);
for (ptr = str; (c = *ptr++) != 0;) // 无缓冲的标准输出
{
putc(c, stdout);
}
}

[/code]

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