Linux系统编程25 目录和用户操作 - 分析目录，读取目录内容的两种方法，glob函数解析

实验1： 使用glob()查找解析目标目录， etc/ 下有多少 以a开头的 .conf文件
实验2： 把目标目录当做目录流 来解析

---

NAME
glob, globfree - find pathnames matching a pattern, free memory from glob()
glob 解析模式或者通配符

SYNOPSIS
#include <glob.h>

/*
	const char *pattern 目标通配文件名
	flags 特殊要求，位图
	int (*errfunc) (const char *epath, int eerrno) 出错的路径和原因
	glob_t *pglob 存放通配的结果
*/
   int glob(const char *pattern, int flags, 
   			int (*errfunc) (const char *epath, int eerrno),
            glob_t *pglob);
   void globfree(glob_t *pglob);

       typedef struct {
           size_t   gl_pathc;    /* Count of paths matched so far  */
           char   **gl_pathv;    /* List of matched pathnames.  */
           size_t   gl_offs;     /* Slots to reserve in gl_pathv.  */
       } glob_t;

实验1： 使用glob()查找解析目标目录， etc/ 下有多少 以a开头的 .conf文件

mhr@ubuntu:~/work/linux/wenjianxitong/20$ 
mhr@ubuntu:~/work/linux/wenjianxitong/20$ ls /etc/a*.conf
/etc/adduser.conf  /etc/apg.conf  /etc/appstream.conf
mhr@ubuntu:~/work/linux/wenjianxitong/20$ 

.

#include <stdio.h>
#include <stdlib.h>
#include <glob.h>

#define PAT "/etc/a*.conf"
//#define PAT "/etc/*"  //  etc 下的所有文件，但不包括隐藏文件
//#define PAT "/etc/.*"  //  etc 下的隐藏文件

#if 0
static int errfunc_(const char *errpath,int eerrno)
{
	puts(errpath);
	fprintf(stderr,"ERROR MSG:%s\n", strerror(eerrno));
	return 0;
}
#endif

int main()
{
	glob_t globres;
	int i,err;

	err = glob(PAT,0,NULL,&globres);
	if(err)
	{
		printf("Error code = %d\n",err);
		exit(1);
	}

	for(i = 0; i < globres.gl_pathc; i++)
		puts(globres.gl_pathv[i]);

	globfree(&globres);
	exit(0);

}

mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ gcc glob.c 
mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ ./a.out
/etc/adduser.conf
/etc/apg.conf
/etc/appstream.conf
mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ 
mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ ls -l /etc/a*.conf
-rw-r--r-- 1 root root 3028 Apr 20  2016 /etc/adduser.conf
-rw-r--r-- 1 root root  112 Jan 10  2014 /etc/apg.conf
-rw-r--r-- 1 root root  389 Apr 18  2016 /etc/appstream.conf
mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ 

---

NAME
opendir, fdopendir - open a directory

SYNOPSIS
#include <sys/types.h>
#include <dirent.h>

   DIR *opendir(const char *name);
   DIR *fdopendir(int fd);

DESCRIPTION
The opendir() function opens a directory stream corresponding to the directory name, and returns a pointer to the directory stream. The stream is positioned at the first entry in the direc‐tory.

The fdopendir() function is like opendir(), but returns a directory stream for the directory referred to by the open file descriptor fd. After a successful call to fdopendir(), fd is used internally by the implementation, and should not otherwise be used by the application.

RETURN VALUE
The opendir() and fdopendir() functions return a pointer to the directory stream. On error, NULL is returned, and errno is set appropriately.

---

CLOSEDIR(3) Linux Programmer’s Manual CLOSEDIR(3)

NAME
closedir - close a directory

SYNOPSIS
#include <sys/types.h>

   #include <dirent.h>

   int closedir(DIR *dirp);

---

READDIR(3) Linux Programmer’s Manual READDIR(3)

NAME
readdir, readdir_r - read a directory

SYNOPSIS
#include <dirent.h>

   struct dirent *readdir(DIR *dirp);
   int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);


      struct dirent {
           ino_t          d_ino;       /* inode number */
           off_t          d_off;       /* not an offset; see NOTES */
           unsigned short d_reclen;    /* length of this record */
           unsigned char  d_type;      /* type of file; not supported
                                          by all filesystem types */
           char           d_name[256]; /* filename */
       };

On success, readdir() returns a pointer to a dirent structure,If the end of the directory stream is reached, NULL is returned and errno is not changed. If an error occurs, NULL is returned and errno is set appropriately.

---

实验2： 把目标目录当做目录流 来解析

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <dirent.h>

#define PAT "/etc"

int main()
{
	DIR *dp;
	struct dirent *cur;
	
	dp = opendir(PAT);
	if(dp == NULL)
	{
		perror("opendir()");
		exit(1);
	}

	while((cur = readdir(dp)) != NULL)
		puts(cur->d_name);
	
	closedir(dp);
	exit(0);
}





mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ 
mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ gcc readdir.c
mhr@ubuntu:~/work/linux/muluheyonghucaozuo/25$ ./a.out 
.
..
printcap
lightdm
sysctl.conf
perl
subuid
nsswitch.conf
machine-id
brltty
acpi
papersize
cupshelpers
brlapi.key
polkit-1
debian_version
libaudit.conf
rc6.d
pm
ghostscript
subgid-
...