📄 操作系统的4个程序.txt
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#include <stdio.h>
main( )
{
int p1,p2;
while((p1=fork( ))= = -1); /*创建子进程p1*/
if (p1==0) putchar('b');
else
{
while((p2=fork( ))= = -1); /*创建子进程p2*/
if(p2==0) putchar('c');
else putchar('a');
}
}
#include <stdio.h>
#include <unistd.h>
main( )
{
int p1,p2,i;
while((p1=fork( ))= = -1); /*创建子进程p1*/
if (p1= =0)
{
lockf(1,1,0); /*加锁，这里第一个参数为stdout（标准输出设备的描述符）*/
for(i=0;i<10;i++)
printf("daughter %d\n",i);
lockf(1,0,0); /*解锁*/
}
else
{
while((p2=fork( ))= =-1); /*创建子进程p2*/
if (p2= =0)
{
lockf(1,1,0); /*加锁*/
for(i=0;i<10;i++)
printf("son %d\n",i);
lockf(1,0,0); /*解锁*/
}
else
{
lockf(1,1,0); /*加锁*/
for(i=0;i<10;i++)
printf(" parent %d\n",i);
lockf(1,0,0); /*解锁*/
}
}
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
void waiting( ),stop( );
int wait_mark;
main( )
{
int p1,p2,stdout;
while((p1=fork( ))= =-1); /*创建子进程p1*/
if (p1>0)
{
while((p2=fork( ))= =-1); /*创建子进程p2*/
if(p2>0)
{
wait_mark=1;
signal(SIGINT,stop); /*接收到^c信号，转stop*/
waiting( );
kill(p1,16); /*向p1发软中断信号16*/
kill(p2,17); /*向p2发软中断信号17*/
wait(0); /*同步*/
wait(0);
printf("Parent process is killed!\n");
exit(0);
}
else
{
wait_mark=1;
signal(17,stop); /*接收到软中断信号17，转stop*/
waiting( );
lockf(stdout,1,0);
printf("Child process 2 is killed by parent!\n");
lockf(stdout,0,0);
exit(0);
}
}
else
{
wait_mark=1;
signal(16,stop); /*接收到软中断信号16，转stop*/
waiting( );
lockf(stdout,1,0);
printf("Child process 1 is killed by parent!\n");
lockf(stdout,0,0);
exit(0);
} }
void waiting( )
{
while(wait_mark!=0);
}
void stop( )
{
wait_mark=0;
}
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
int pid1,pid2;
main( )
{
int fd[2];
char outpipe[100],inpipe[100];
pipe(fd); /*创建一个管道*/
while ((pid1=fork( ))= =-1);
if(pid1= =0)
{
lockf(fd[1],1,0);
sprintf(outpipe,"child 1 process is sending message!");
/*把串放入数组outpipe中*/
write(fd[1],outpipe,50); /*向管道写长为50字节的串*/
sleep(5); /*自我阻塞5秒*/
lockf(fd[1],0,0);
exit(0);
}
else
{
while((pid2=fork( ))= =-1);
if(pid2= =0)
{ lockf(fd[1],1,0); /*互斥*/
sprintf(outpipe,"child 2 process is sending message!");
write(fd[1],outpipe,50);
sleep(5);
lockf(fd[1],0,0);
exit(0);
}
else
{ wait(0); /*同步*/
read(fd[0],inpipe,50); /*从管道中读长为50字节的串*/
printf("%s\n",inpipe);
wait(0);
read(fd[0],inpipe,50);
printf("%s\n",inpipe);
exit(0);
}
}
}
1)进程的软中断通信
<任务1>
编制一段程序,使用系统调用fork()创建两个子进程,再用系统调用signal()让父进程捕捉键盘上来的中断信号(即按Del键),当捕捉到中断信号后,父进程用系统调用kill() 向两个子进程发出信号,子进程捕捉到信号后,分别输出下列信息后终止：
child process l is killed by parent!
child process 2 is killed by parent!
父进程等待两个子进程终止后,输出以下信息后终止：
parent process is killed!
(程序)
/*e-1-31*/
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
int wait_flag;
void stop();
main() {
int pid1,pid2;
signal(3,stop); //or signal(14,stop);
while((pid1=fork())==-1);
if(pid1>0) {
while((pid2=fork())==-1);
if(pid2>0) {
// wait_flag=1;
sleep(5);
kill(pid1,16);
kill(pid2,17);
wait(0);
wait(0);
printf("Parent process is killed !!\n");
exit(0);
}
else {
// wait_flag=1;
signal(17,stop);
printf("Child process 2 is killed by parent !!\n");
exit(0);
}
}
else {
// wait_flag=1;
signal(16,stop);
printf("Child process 1 is killed by parent !!\n");
exit(0);
}
}
void stop() {
wait_flag=0;
}
(运行结果)
child process 1 is killed by parent!
child process 2 is killed by parent!
Parent process is killed!
分析
(1)上述程序中,实用函数signal()都放在一段程序的前面部位,而不是在其他接收信号处。这是因为signal()的执行只是为进程指定信号量16或17的作用,以及分配相应的与 stop()过程链接的指针。从而signal()函数必须在程序前面部分执行。
(2)该程序段前面部分用了两个wait(0),为什么?请读者思考。
(3)该程序段中每个进程退出时都用了语句exit(0),为什么?请读者思考。
<任务2>
在上面任务1中,增加语句signal(SIGINT,SIG_IGN)和语句signal(SIGQUIT, SIG_IGN),观察执行结果,并分析原因。这里signal(SIGINT,SIG_IGN)和signal(SIGQUIT,SIG_IGN)分别为忽略'Del'键信号以及忽略中断信号。
(程序)
/*e-1-32*/
#include<unistd.h>
#include<signal.h>
#include<stdio.h>
int pid1,pid2;
int EndFlag=0;
//pf1=0;
//pf2=0;
void IntDelete()
{
kill(pid1,10);
kill(pid2,12);
EndFlag=1;
}
void Int1()
{
printf("child process 1 is killed ! by parent\n");
exit(0);
}
void Int2()
{
printf("child process 2 is killed ! by parent\n");
exit(0);
}
waiting()
{ while(EndFlag==0);}
main()
{
//int exitpid;
signal(SIGINT,SIG_IGN);
signal(SIGQUIT,SIG_IGN);
while((pid1=fork())==-1);
if(pid1==0)
{
//signal(SIGINT,SIG_IGN);
signal(10,Int1);
signal(SIGINT,SIG_IGN);
pause();
exit(0);
}
else
{
while((pid2=fork())==-1);
if(pid2==0)
{
//signal(SIGINT,SIG_IGN);
signal(12,Int2);
signal(SIGINT,SIG_IGN);
pause();
exit(0);
}
else
{
signal(SIGINT,IntDelete);
//waitpid(-1,&exitcode,0);
waiting();
printf("parent process is killed\n");
exit(0);
}
}
}
<运行结果>
请读者将上述程序输入计算机后,执行并观察。
<分析> 由于忽略了中断与退出信号,程序会一直保持阻塞状态而无法退出。
2)进程的管道通信
(任务)
编制一段程序,实现进程的管道通信。使用系统调用pipe()建立一条管道线。两个子进程p1和p2分别向管道各写一句话：
child 1 is sending message!
child 2 is sending message!
而父进程则从管道中读出来自于两个子进程的信息,显示在屏幕上。
(程序)
/*e-1-4*/
#include<unistd.h>
#include<signal.h>
#include<stdio.h>
int pid1,pid2;
main()
{
int fd[2];
char OutPipe[100],InPipe[100];
pipe(fd);
while((pid1=fork())==-1);
if(pid1==0)
{
lockf(fd[1],1,0);
sprintf(OutPipe,"child 1 process is sending message!");
write(fd[1],OutPipe,50);
sleep(5);
lockf(fd[1],0,0);
exit(0);
}
else
{
while((pid2=fork())==-1);
if(pid2==0)
{
lockf(fd[1],1,0);
sprintf(OutPipe,"child 2 proeess is sending message!");
write(fd[1],OutPipe,50);
sleep(5);
lockf(fd[1],0,0);
exit(0);
}
else
{
wait(0);
read(fd[0],InPipe,50);
printf("%s\n",InPipe);
wait(0);
read(fd[0],InPipe,50);
printf("%s\n",InPipe);
exit(0);
}
}
}
(运行结果)
child 1 is sending message!
child 2 is sending message!
(分析)
请读者自行完成。
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