【C】——APUE小程序之递归遍历目录

　　递归降序遍历目录层次结构，并按文件类型计数。

　　先介绍相关的函数：

#include<dirent.h>

DIR *opendir(const char *pathname);        //打开目录
返回值：成功返回指针，出错返回NULL

struct dirent *readdir(DIR *dp);               //读取目录
返回值：成功返回指针，出错返回NULL

void rewinddir(DIR *dp);                           //重设读取目录的位置为开头位置

int closedir(DIR *dp);                             //关闭目录
返回值：成功返回0，出错返回-

long telldir(DIR *dp);                            //取得目录流的读取位置
返回值：与dp关联的目录中的当前位置

void seekdir(DIR *dp, long loc);              //设置下回读取目录的位置

struct dirent{
     ino_t d_ino;                         //i-node number
     char   d_name[NAME_MAX + ];            //null-terminated filename
}

　　改写APUE的代码：

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

 static int nreg = , ndir = , nblk = , nchr = , nfifo = , nslink = , nsock = , ntot = ;

 static char *fullpath;

 int myfunc(const char *pathname, const struct stat *statptr, int type)
 {
     switch(type){
     case :
         switch(statptr->st_mode & S_IFMT){
         case S_IFREG: nreg++;    break;
         case S_IFBLK: nblk++;    break;
         case S_IFCHR: nchr++;    break;
         case S_IFIFO: nfifo++;    break;
         case S_IFLNK: nslink++;    break;
         case S_IFSOCK: nsock++;    break;
         case S_IFDIR:{
             printf("for S_IFDIR for %s\n",pathname);
             }
         }
         break;
     case :        //文件夹
         ndir++;    break;
     case :
         printf("cant read directory %s\n",pathname);
     case :
         printf("stat error for %s\n",pathname);
     }

     return ;
 }

 int dopath()
 {
     struct stat     statbuf;        //文件信息
     struct dirent     *dirp;        //文件夹信息，包括i-node number   filename
     DIR         *dp;        //打开目录返回的指针
     char         *ptr;

     if((lstat(fullpath,&statbuf)) < )
         return(myfunc(fullpath,&statbuf,));
     if(S_ISDIR(statbuf.st_mode) == )        //判断是否是文件夹
         return(myfunc(fullpath,&statbuf,));

     myfunc(fullpath,&statbuf,);            //是目录则调用函数使目录数量自加一

     ptr = fullpath + strlen(fullpath);
     *ptr++ = '/';
     *ptr = ;

     if((dp = opendir(fullpath)) == NULL)
         return(myfunc(fullpath,&statbuf,));

     while((dirp = readdir(dp)) != NULL){
         if(strcmp(dirp->d_name,".") ==  || strcmp(dirp->d_name,"..") == )
             continue;
         strcpy(ptr, dirp->d_name);

         dopath();
     }

     closedir(dp);

 }

 void ftw(char *pathname)
 {
 #ifdef PATH_MAX
     const int PATH_LEN = PATH_MAX;
 #else
     const int PATH_LEN = ;
 #endif

     fullpath = malloc(PATH_LEN);

     strncpy(fullpath,pathname,PATH_LEN);

     fullpath[PATH_LEN - ] = '\0';

     dopath();
 }

 int main(int argc, char *argv[])
 {
     if(argc != ){
         printf("enter two args\n");
         exit();
     }

     ftw(argv[]);

     printf("regular files: }\n",nreg);
     printf("directories : }\n",ndir);
     printf("block special: }\n",nblk);
     printf("char special: }\n",nchr);
     printf("FIFOS: }\n",nfifo);
     printf("symboli links: }\n",nslink);
     printf("sockets: }\n",nsock);

 }

　　需要注意的是第60行的判断一定不能少，因为在linux下创建一个空目录的时候，用ls查看其属性发现里面大小是2.写一个程序看下一个空目录里都有神马？

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

 int main(int argc, char *argv[])
 {
     DIR *dp;
     struct dirent *dirp;
     char pathname[];

     if(argc != ){
         printf("please enter to args\n");
         exit();
     }

     puts(argv[]);

     strncpy(pathname, argv[], );

     if((dp = opendir(pathname)) == NULL){
         printf("opendir %s error\n",argv[]);
         exit();
     }

     while((dirp = readdir(dp)) != NULL){
         printf("%s\n",dirp->d_name);
     }

     closedir(dp);

     return ;
 }

　　虽然是个空目录但是给的结果却是

.

..

　　因此要忽略掉这两个，否则会进入死循环；