Lab1-Xv6 and Unix utilities

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sleep(esay)

  1. 根据提示查看user/echo.c的写法

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    //echo.c
    #include "kernel/types.h"
    #include "kernel/stat.h"
    #include "user/user.h"

    int
    main(int argc, char *argv[])
    {
      int i;

      for(i = 1; i < argc; i++){
        write(1, argv[i], strlen(argv[i]));
        if(i + 1 < argc){
          write(1, " ", 1);
        } else {
          write(1, "\n", 1);
        }
      }
      exit(0);
    }
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    //rm.c
    #include "kernel/types.h"
    #include "kernel/stat.h"
    #include "user/user.h"

    int
    main(int argc, char *argv[])
    {
      int i;

      if(argc < 2){
        fprintf(2, "Usage: rm files...\n");
        exit(1);
      }

      for(i = 1; i < argc; i++){
        if(unlink(argv[i]) < 0){
          fprintf(2, "rm: %s failed to delete\n", argv[i]);
          break;
        }
      }

      exit(0);
    }

  2. 编写sleep.c

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    #include "kernel/types.h"
    #include "kernel/stat.h"
    #include "user/user.h"

    int main(int argc,char *argv[])
    {
        if(argc==1)
        {
            write(1,"error:missing argument\n",24);
            exit(1);
        }
        int n = atoi(argv[1]);
        sleep(n);
        exit(0);
    }

  3. 在Makefile中添加sleep.c
    image-20221221135738521

  4. 运行测试
    image-20221221151232885
    输入sleep 10会等待一会才出现命令提示符，忘记输入参数会报错。

  5. 提交
    image-20221221151455714
    提交发现三个测试点全部通过。

pingpong(esay)

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#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"

int main()
{
	int p[2];
	char buf[512];
	pipe(p);
	if(fork()==0)
	{
		read(p[0],buf,sizeof buf);
		write(p[1],"this is child",13);
		printf("%d: received ping\n",getpid());	
//		printf("--\n%s\n",buf);
		exit(0);
	}
	else
	{
		write(p[1],"this is parent",14);
		wait(0);
		read(p[0],buf,sizeof buf);
		printf("%d: received pong\n",getpid());
//		printf("++\n%s\n",buf);
		exit(0);
	}

}

主要是进程间通过管道通信。

提交结果：

image-20221221154512781

primes (moderate)/(hard)

类似于素数筛的程序，不过下面的程序一直会停在第二层。

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#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "stddef.h"
int* process(int pl[])
{
	printf("start!\n");
	int num,now_prime;
	int pr[2];
	int cnt =0;
	int st = 0;
	pipe(pr);
	printf("create pipe\n");
	int statue;
	printf("pl[0] is %d\npl[1] is %d\n",pl[0],pl[1]);
	statue = read(pl[0],&num,4);
	printf("have read\n");
	while(statue)
	{	
		printf("%d***%d\n",statue,num);	
		if(cnt==0)
		{	
			now_prime = num;
			printf("prime %d\n",num);
		}
		else
		{
			if(num%now_prime!=0)
			{
				
				write(pr[1],&num,sizeof num);
			}
		}
		cnt+=1;
		st = 1;
		statue = read(pl[0],&num,4);
	}
//	close(pl[0]);
//	close(pr[1]);
	int *res = NULL;
	if(st)
		res = pr;
	return res;
}

int main()
{
	int pl[2];
	int *p=NULL;
	pipe(pl);
	close(pl[0]);
	for(int i =2;i<=5;i++)
	{
//		char *next = itoa(i);
		write(pl[1],&i,sizeof i);
	}
 	close(pl[1]);
	p = process(pl);
	printf("%d\n",p);
	printf("first p[0] is %d,p[1] is %d\n",p[0],p[1]);
	while(p!=NULL)
	{			
		printf("%d\n",p);
		printf("ex1 p[0] is %d,p[1] is %d\n",p[0],p[1]);
		if(fork()==0)
		{
			printf("===\n");
			printf("ex p[0] is %d,p[1] is %d\n",p[0],p[1]);
			p = process(p);
			printf("---\n");
			exit(0);
		}
		else
		{
//			while(wait(0)!=-1);
			wait(0);
			exit(0);
		}
	}
	exit(0);
}

正确做法：

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#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
void process(int *lastfp)
{
	close(lastfp[1]);
	int num,p;
	int fp[2];
	if(read(lastfp[0],&p,4))
	{
		printf("prime %d\n",p);
		pipe(fp);
		if(fork()==0)
		{
			process(fp);
		}
		else
		{
			close(fp[0]);
			while(read(lastfp[0],&num,4))
			{
				if(num%p!=0)
                        	{
                                	write(fp[1],&num,sizeof num);
                          	}

			}
			close(fp[1]);
			wait(0);
			exit(0);
		}
	}
	else
	{
		
	}
	close(lastfp[0]);
	exit(0);
}
int main()
{
	int fp[2];
	pipe(fp);
	if(fork()==0)
	{
		process(fp);
	}
	else
	{
		close(fp[0]);
		for(int i = 2;i<=35;i++)
		{
			write(fp[1],&i,sizeof i);
		}
		close(fp[1]);
		wait(0);
	}
	exit(0);
}

提交结果

image-20221222112626733

find (moderate)

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#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "kernel/fs.h"



void find(char *path,char *x)
{
	char buf[512],*p;
	int fd;
	struct dirent de;
	struct stat st;

	if((fd=open(path,0))<0)
	{
		fprintf(2, "find: cannot open %s\n", path);
		return;
	}
	if(fstat(fd, &st) < 0)
	{
		fprintf(2, "find: cannot stat %s\n", path);
	    	close(fd);
    		return;
  	}
	strcpy(buf,path);
	p = buf+strlen(buf);
	*p++='/';
	while(read(fd,&de,sizeof de)==sizeof de)
	{
		if (de.inum==0||strcmp(de.name,".")==0||strcmp(de.name,"..")==0)
			continue;
		memmove(p,de.name,DIRSIZ);
		p[DIRSIZ]=0;
		if (stat(buf,&st)<0)
		{
			fprintf(2,"find: cannot stat %s\n",buf);
			continue;
		}
		
	
		switch(st.type)
		{
			case T_FILE:
				if(strcmp(de.name,x)==0)
					printf("%s\n",buf);
				break;
			case T_DIR:
				find(buf,x);
				break;
		}
	}
	close(fd);
	return ;
}

int main(int argc,char *argv[])
{
	char *path = argv[1];
	char *x = argv[2];
//	printf("%s %s\n",path,x);
	find(path,x);
	exit(0);
}

两个结构体分别定义在kernel/stat.h和kernel/fs.h中

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// stat.h
#define T_DIR     1   // Directory
#define T_FILE    2   // File
#define T_DEVICE  3   // Device

struct stat {
  int dev;     // File system's disk device
  uint ino;    // Inode number
  short type;  // Type of file
  short nlink; // Number of links to file
  uint64 size; // Size of file in bytes
};




//fs.h(部分)
// Directory is a file containing a sequence of dirent structures.
#define DIRSIZ 14

struct dirent {
  ushort inum;
  char name[DIRSIZ];
};

memmove()和memcpy()功能一样，区别在于memcpy()会一个一个复制，而memmove()会先将数据复制到中间缓冲区，然后再从缓冲区复制到目的地。

提交结果：

image-20221222183528256

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