unix环境高级编程-4.21-读目录

本节主要讲述了对unix系统对读目录的讲述。首先了解一下了解一下下面的函数

#include <dirent.h>DIR* opendir(const char* pathname);                    成功返回指针，错误返回null；struct dirent *readdir(DIR *dp);//成功返回其指针，若在目录结尾或出错则返回null;void rewinddir(DIR* dp);int closedir(DIR* dp);//成功返回0，出错返回-1；long telldir(DIR* dp);//////返回与dp关联的目录中的当前的位置void seekdir(DIR * dp,long loc);

 

struct dirent * readdir (DIR *dirstream) [Function]
This function reads the next entry from the directory. It normally returns a pointer to
a structure containing information about the file. This structure is statically allocated
and can be rewritten by a subsequent call.
Portability Note: On some systems readdir may not return entries for ‘.’ and ‘..’,
even though these are always valid file names in any directory. See Section 11.2.2
[File Name Resolution], page 224.
If there are no more entries in the directory or an error is detected, readdir returns
a null pointer. The following errno error conditions are defined for this function:
EBADF The dirstream argument is not valid.
readdir is not thread safe. Multiple threads using readdir on the same dirstream
may overwrite the return value. Use readdir_r when this is critical.

 

 

int closedir (DIR *dirstream) [Function]
This function closes the directory stream dirstream. It returns 0 on success and -1
on failure.
The following errno error conditions are defined for this function:
EBADF The dirstream argument is not valid.

其他的就不写了，本章主要是通过运用以上函数来实现遍历目录层次结构，并按文件类型进行技术。

 

直接上代码：

#include "apue.h"#include <dirent.h>#include<limits.h>typedef int Myfunc(const char* ,const struct stat* ,int);static Myfunc myfunc;static int myftw(char* ,Myfunc*);static int dopath(Myfunc *);static long nreg,ndir,nblk,nchr,nfifo,nslink,nsock,ntot;int main(int argc,char** argv){    int ret;    if(argc!=2)        err_quit("usage:ftw<starting-pathname>");    ret=myftw(argv[1],myfunc);    ntot=nreg+ndir+nblk+nchr+nfifo+nslink+nsock;    if(ntot==0)        ntot=1;    printf("regular files= %7ld,%5.2f %%\n",nreg,nreg*100.0/ntot);    printf("regular files= %7ld,%5.2f %%\n",ndir,ndir*100.0/ntot);    printf("regular files= %7ld,%5.2f %%\n",nblk,nblk*100.0/ntot);    printf("regular files= %7ld,%5.2f %%\n",nchr,nchr*100.0/ntot);    printf("regular files= %7ld,%5.2f %%\n",nfifo,nfifo*100.0/ntot);    printf("regular files= %7ld,%5.2f %%\n",nslink,nslink*100.0/ntot);    printf("regular files= %7ld,%5.2f %%\n",nsock,nsock*100.0/ntot);}char*path_alloc(int* size) { char *p = NULL; if(!size) return NULL; p = malloc(256); if(p) *size = 256; else *size = 0; return p; } #define FTW_F 1 #define FTW_D 2 #define FTW_DNR 3 #define FTW_NS 4 static char *fullpath; static int myftw(char* pathname,Myfunc* func) {    int len;    fullpath=path_alloc(&len);    strncpy(fullpath,pathname,len);    fullpath[len-1]=0;    return (dopath(func)); } static int dopath(Myfunc* func) {    struct stat statbuf;    struct dirent *dirp;    DIR* dp;    int ret;    char *ptr;    if(lstat(fullpath,&statbuf)<0)        return (func(fullpath,&statbuf,FTW_NS));    if(S_ISDIR(statbuf.st_mode)==0)        return (func(fullpath ,&statbuf, FTW_F));        if((ret=func(fullpath,&statbuf,FTW_D))!=0)        return (ret);     ptr=fullpath+strlen(fullpath);     *ptr++='/';     *ptr=0;     if((dp=opendir(fullpath))==NULL)        return(func(fullpath,&statbuf,FTW_DNR));      while((dirp=readdir(dp))!=NULL){          if(strcmp(dirp->d_name,".")==0||             strcmp(dirp->d_name,"..")==0)             continue;         strcpy(ptr,dirp->d_name);         if((ret=dopath(func))!=0)            break;          }        ptr[-1]=0;        if(closedir(dp)<0)            err_ret("can't clost dir %s",fullpath);        return(ret); } static int myfunc(const char* pathname,const struct stat* statptr,int type) {    switch(type)    {        case FTW_F:           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:                  err_dump("for S_IFDIR for %s",pathname);            }            break;        case FTW_D:             ndir++;             break;        case FTW_DNR:             err_ret("can't read directory %s",pathname);             break;        case FTW_NS:             err_ret("stat error for %s",pathname);             break;        default:             err_dump("unkown type %d for pathname %s",type,pathname);        }        return(0); }

这个经过修正可以正常运行了

运行结果