《Linux程序设计 第四版》之第三章的练习题

1、P103

一个目录扫描程序。

#include<stdio.h>
#include<dirent.h>
#include<sys/stat.h>

int isAdir(char* path);    //判断路径是否是目录类型
void printdirs(char* path,int depth)   //递归遍历打印文件与目录名
{

	DIR* dir=opendir(path);
	struct dirent* dirents;
	chdir(path);
	while(dirents=readdir(dir))
	{
	if(isAdir(dirents->d_name))
	{
	if(strcmp(".",dirents->d_name)==0||strcmp("..",dirents->d_name)==0)
		continue;
		printf("%*s%s/ \n",depth," ",dirents->d_name);
		printdirs(dirents->d_name,depth+1);

	}
	else
		printf("%*s%s/ \n",depth," ",dirents->d_name);
	}
	chdir("..");
	closedir(dir);

}
int isAdir(char* path)
{
	struct stat statbuff;
	//printf("%s",path);
	lstat(path,&statbuff);

	if(S_ISDIR(statbuff.st_mode))
		{

		return 1;
		}

	return 0;

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

	/* char* path[1023];
	gets(path);          //用户在程序中自己输入的Path
	chdir(path);*/
	char* path=".";     //用程序的参数当path
	if(argc >=2)
	{
	path = argv[1];
	}

	if(isAdir(path)==1)
		{
		printdirs(path,0);
		perror("wrong::");
		return 1;
		}
	printf("path is not a dir");

	return 1;

}

2、P112

使用mmap函数程序，来修改文件内容，将文件映射到内存，并且看成数组进行更改！

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/mman.h>
#define recordNum (50)
struct Record       //记录的结构
{
int integ;
char string[15];
}Record;
int creatfile(char* file)
{
	struct Record r;
	FILE* fp=fopen(file,"w+");
	int i=0;
	for(;i<50;i++)
	{
		r.integ=i;
		memset(r.string,0,15);
		sprintf(r.string,"Record-%d",i);   //格式化字符串输入到r.string中
		fwrite(&r,sizeof( r),1,fp);
	}
	fclose(fp);

}
void memomap(char* file)
{
	struct Record rECORD,*r;
	int f=open(file,O_RDWR);
	r=(struct Record *)mmap( 0 , recordNum*sizeof(struct Record), PROT_READ|PROT_WRITE, MAP_SHARED , f,0);   //内存映射函数
	r[20].integ=100;
	sprintf(r[20].string,"Record-%d",r[20].integ);
	msync((void*)r,recordNum*sizeof(rECORD),MS_SYNC);               //将该内存段的修改保存回文件中
	munmap((void*)r,recordNum*sizeof(rECORD));						//释放内存段
	close(f);
	return;
}

int main(int argc,char* argv[])
{
creatfile("records.date");
memomap("records.date");

	return 1;

}