experiment_2.c

初学Linux的很好的练习程序

/*exc2.c实验二源码*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
#include <syslog.h>
#define MAXFILE 65535
int main(void)
{
	pid_t child1,child2;
	int i;
	child1 = fork();
/*创建子进程1*/
	if( child1 == -1 ){
		perror("child1 fork");
		exit(1);
	}
	else if( child1 > 0 )
		exit( 0 );
/*打开日志服务*/
	openlog("exc2_info", LOG_PID, LOG_DAEMON);
/*以下几步是编写守护进程的常规步骤*/
	setsid();
	chdir( "/" );
	umask( 0 );
	for( i = 0 ; i < MAXFILE ; i++ )
	{
		close( i );
	}
/*创建子进程2*/
	child2 = fork();
	if( child2 == -1 ){
		perror("child2 fork");
		exit(1);
	}
	else if( child2 == 0 ){
/*在日志中写入字符串*/
		syslog( LOG_INFO, " child2 will sleep for 10s ");
		sleep(10);
		syslog( LOG_INFO, " child2 is going to exit! ");
		exit(0);
	}
	else{
		waitpid( child2, NULL, 0);
		syslog( LOG_INFO , " child1 noticed that child2 has exited " );
/*关闭日志服务*/
		closelog();
		while(1){
			sleep(10);
		}	
	}
}