第十二周学习报告

第十二周（11.23-11.29）:

一、学习目标

掌握进程控制
掌握信号处理的方法
掌握管道和fifo进行进程间通信的方法

二、学习资源

编译、运行、阅读、理解process.tar.gz压缩包中的代码

三、学习任务
（提示：请将要求学生完成的任务、测验或思考题列在此处）

编译、运行、阅读、理解process.tar.gz压缩包中的代码

一些头文件的用处：

stdio.h	标准输入输出
stdlib.h	C标准函数库
unistd.h	Unix类系统定义符号常量

exec1

#include <stdio.h>
#include <unistd.h>
int main()
{
char	*arglist[3];
arglist[0] = "ls";
arglist[1] = "-l";
arglist[2] = 0 ;//NULL
printf("* * * About to exec ls -l
");//不成功调用exevp，返回-1
execvp( "ls" , arglist );
printf("* * * ls is done. bye");
return 0;
}

• 没打印出“* * * ls is done. bye”这句话

exec2

#include <stdio.h>
#include <unistd.h>
int main()
{
char	*arglist[3];
arglist[0] = "ls";
arglist[1] = "-l";
arglist[2] = 0 ;
printf("* * * About to exec ls -l
");
execvp( arglist[0] , arglist );
printf("* * * ls is done. bye
");
}

• 运行结果同1

exec3

#include <stdio.h>
#include <unistd.h>
int main()
{
char	*arglist[3];
char    *myenv[3];
myenv[0] = "PATH=:/bin:";
myenv[1] = NULL;
arglist[0] = "ls";
arglist[1] = "-l";
arglist[2] = 0 ;
printf("* * * About to exec ls -l
");
execlp("ls", "ls", "-l", NULL);
printf("* * * ls is done. bye
");
}

• 运行结果同1

forkdemo1

#include	<stdio.h>
#include    <sys/types.h>
#include    <unistd.h>
int main()
{
int	ret_from_fork, mypid;
mypid = getpid();			   
printf("Before: my pid is %d
", mypid);//打印PID
ret_from_fork = fork();//一次调用fork
sleep(1);//休息一秒
printf("After: my pid is %d, fork() said %d
",
		getpid(), ret_from_fork);//父进程打印子进程PID
return 0;
}

forkdemo2

#include <stdio.h>
#include <unistd.h>
int main()
{
printf("before:my pid is %d
", getpid() );
fork();//第一次调用fork
fork();//第二次调用fork
printf("aftre:my pid is %d
", getpid() );//输出四次aftre
return 0;
}

foekdemo3

#include	<stdio.h>
#include    <stdlib.h>
#include    <unistd.h>
int main()
{
int	fork_rv;

printf("Before: my pid is %d
", getpid());

fork_rv = fork();		/* create new process	*/

if ( fork_rv == -1 )		/* check for error	*/
	perror("fork");
else if ( fork_rv == 0 ){ 
	printf("I am the child.  my pid=%d
", getpid());

	exit(0);
}
else{
	printf("I am the parent. my child is %d
", fork_rv);
	exit(0);
}
return 0;
}

• 先输出父亲进程PID
• 表面身份并输出子进程PID

forkdemo4

#include	<stdio.h>
#include    <stdlib.h>
#include    <unistd.h>
int main()
{
int	fork_rv;
printf("Before: my pid is %d
", getpid());
fork_rv = fork();		/* create new process	*/
if ( fork_rv == -1 )		/* check for error	*/
	perror("fork");
else if ( fork_rv == 0 ){ 
	printf("I am the child.  my pid=%d
", getpid());
	printf("parent pid= %d, my pid=%d
", getppid(), getpid());
	exit(0);
}
else{
	printf("I am the parent. my child is %d
", fork_rv);
	sleep(10);
	exit(0);
}
return 0;
}

• 输出父亲进程PID
• 表明身份，输出PID
• 总结父进程和子进程PID

forkgdb

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int  gi=0;
int main()
{
int li=0;
static int si=0;
int i=0;
pid_t pid = fork();
if(pid == -1){
	exit(-1);
}
else if(pid == 0){
	for(i=0; i<5; i++){
		printf("child li:%d
", li++);
		sleep(1);
		printf("child gi:%d
", gi++);
		printf("child si:%d
", si++);
	}
	exit(0);	
}
else{
	for(i=0; i<5; i++){
		printf("parent li:%d
", li++);
		printf("parent gi:%d
", gi++);
		sleep(1);
		printf("parent si:%d
", si++);
	}
exit(0);	
}
return 0;
}

• 该程序是并发执行的
• 当一个程序执行时，另一个程序在休眠交替

psh1

#include	<stdio.h>
#include	<stdlib.h>
#include	<string.h>
#include    <unistd.h>

#define	MAXARGS		20				
#define	ARGLEN		100				

int execute( char *arglist[] )
{
execvp(arglist[0], arglist);		
perror("execvp failed");
exit(1);
}
char * makestring( char *buf )
{
char	*cp;
buf[strlen(buf)-1] = '';		
cp = malloc( strlen(buf)+1 );		
if ( cp == NULL ){			
	fprintf(stderr,"no memory
");
	exit(1);
}
strcpy(cp, buf);		
return cp;			
}
int main()
{
char	*arglist[MAXARGS+1];		
int		numargs;			
char	argbuf[ARGLEN];			
numargs = 0;
while ( numargs < MAXARGS )
{					
	printf("Arg[%d]? ", numargs);
	if ( fgets(argbuf, ARGLEN, stdin) && *argbuf != '
' )
		arglist[numargs++] = makestring(argbuf);
	else
	{
		if ( numargs > 0 ){		
			arglist[numargs]=NULL;	
			execute( arglist );	
			numargs = 0;		
		}
	}
}
return 0;
}

• 手动输入指令，回车表示结束

push2

• 同push1，多了循环

testbuf1

#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("hello");
fflush(stdout);
while(1);
}

• 输出：
  

testbuf2

#include <stdio.h>
int main()
{
printf("hello
");
while(1);
}

• 输出同testbuf1

testbuf3

 #include <stdio.h>
int main()
{
fprintf(stdout, "1234", 5);
fprintf(stderr, "abcd", 4);
}

• 输出：
  

testpid

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>	
int main()
{
printf("my pid: %d 
", getpid());//输出进程PID
printf("my parent's pid: %d 
", getppid());//输出父亲进程PID
return 0;
}

• 输出见代码分析

testpp

#include <stdio.h>
#include <stdlib.h>
int main()
{
char **pp;
pp[0] = malloc(20);
return 0;
}

• 输出
  

testsystem

#include	<stdlib.h>
int main ( int argc, char *argv[] )
{
system(argv[1]);
system(argv[2]);
return EXIT_SUCCESS;
}				/* ----------  end of function main  ---------- */

waitdemo

#include	<stdio.h>
#include    <stdlib.h>
#include    <sys/types.h>
#include    <sys/wait.h>
#include    <unistd.h>
#define	DELAY	4
void child_code(int delay)
{
printf("child %d here. will sleep for %d seconds
", getpid(), delay);
sleep(delay);
printf("child done. about to exit
");
exit(17);
}
void parent_code(int childpid)
{
int wait_rv=0;		/* return value from wait() */
wait_rv = wait(NULL);
printf("done waiting for %d. Wait returned: %d
", 
		childpid, wait_rv);
}
int main()
{
int  newpid;
printf("before: mypid is %d
", getpid());
if ( (newpid = fork()) == -1 )
	perror("fork");
else if ( newpid == 0 )
	child_code(DELAY);
else
	parent_code(newpid);
return 0;
}

• 输出当前进程
• 当子进程存在，则终止子进程，输出子进程PID

waitdemo2

 #include	<stdio.h>
 #include    <stdlib.h>
 #include    <sys/types.h>
 #include    <sys/wait.h>
 #include    <unistd.h>
 #define	DELAY	10
 void child_code(int delay)
{
printf("child %d here. will sleep for %d seconds
", getpid(), delay);
sleep(delay);
printf("child done. about to exit
");
exit(27);
 }
void parent_code(int childpid)
{
int wait_rv;	
int child_status;
int high_8, low_7, bit_7;
wait_rv = wait(&child_status);
printf("done waiting for %d. Wait returned: %d
", childpid, wait_rv);
high_8 = child_status >> 8;     /* 1111 1111 0000 0000 */
low_7  = child_status & 0x7F;   /* 0000 0000 0111 1111 */
bit_7  = child_status & 0x80;   /* 0000 0000 1000 0000 */
printf("status: exit=%d, sig=%d, core=%d
", high_8, low_7, bit_7);
}
int main()
{
int  newpid;
printf("before: mypid is %d
", getpid());
if ( (newpid = fork()) == -1 )
	perror("fork");
else if ( newpid == 0 )
	child_code(DELAY);
else
	parent_code(newpid);
}

• 输出结果同1

environvar

#include <stdio.h>
int main(void)
{
extern char **environ;
int i;
for(i = 0; environ[i] != NULL; i++)
	printf("%s
", environ[i]);
return 0;
}

• 输出所用的所有的详细信息