小记——linux目录

布满荆棘的人生 2022-09-23 14:00 271阅读 0赞

1. 获取当前目录

#include <unistd.h>
    char * getcwd (char *buf, size_t size);

==>例程：获取当前目录（POSIX版本）

char cwd[BUF_LEN];
    if (!getcwd (cwd, BUF_LEN)) {
    perror ("getcwd");
    exit (EXIT_FAILURE);
    }
    printf ("cwd = %s\n", cwd);

==>例程：获取当前目录（linux版本）

char *cwd;
    cwd = getcwd (NULL, 0);
    if (!cwd) {
    perror ("getcwd");
    exit (EXIT_FAILURE);
    }
    printf ("cwd = %s\n", cwd);
    free (cwd);

2. 改变当前目录

#include <unistd.h>
    int chdir (const char *path);
    int fchdir (int fd);

==>例程：改变当前目录与恢复  
The most common use of getcwd() is to save the current working directory so that the process can return to it later. For example:

char *swd;
    int ret;
    /* save the current working directory */
    swd = getcwd (NULL, 0);
    if (!swd) {
    perror ("getcwd");
    exit (EXIT_FAILURE);
    }
    /* change to a different directory */
    ret = chdir (some_other_dir);
    if (ret) {
    perror ("chdir");
    exit (EXIT_FAILURE);
    }
    /* do some other work in the new directory... */
    /* return to the saved directory */
    ret = chdir (swd);
    if (ret) {
    perror ("chdir");
    exit (EXIT_FAILURE);
    }
    free (swd);

另一个更高效的版本：

int swd_fd;
    swd_fd = open (".", O_RDONLY);
    if (swd_fd == −1) {
    perror ("open");
    exit (EXIT_FAILURE);
    }
    /* change to a different directory */
    ret = chdir (some_other_dir);
    if (ret) {
    perror ("chdir");
    exit (EXIT_FAILURE);
    }
    /* do some other work in the new directory... */
    /* return to the saved directory */
    ret = fchdir (swd_fd);
    if (ret) {
    perror ("fchdir");
    exit (EXIT_FAILURE);
    }
    /* close the directory's fd */
    ret = close (swd_fd);
    if (ret) {
    perror ("close");
    exit (EXIT_FAILURE);
    }

通过利用fd，内核可以直接操纵inode，所以效率更高。  
  
3. 创建目录

#include <sys/stat.h>
    #include <sys/types.h>
    int mkdir (const char *path, mode_t mode);

4. 删除目录

#include <unistd.h>
    int rmdir (const char *path);

仅对空目录有才会成功  
  
5. 读取目录内容

#include <sys/types.h>
    #include <dirent.h>
    DIR * opendir (const char *name);

DIR是一个目录流

5.1 读取目录流

#include <sys/types.h>
    #include <dirent.h>
    struct dirent * readdir (DIR *dir);

struct dirent {
    ino_t d_ino; /* inode number */
    off_t d_off; /* offset to the next dirent */
    unsigned short d_reclen; /* length of this record */
    unsigned char d_type; /* type of file */
    char d_name[256]; /* filename */
    };

5.2 关闭目录流

#include <sys/types.h>
    #include <dirent.h>
    int closedir (DIR *dir);

==>例程：查找目录中是否有特定的文件

/*
    * find_file_in_dir - searches the directory 'path' for a
    * file named 'file'.
    *
    * Returns 0 if 'file' exists in 'path' and a nonzero
    * value otherwise.
    */
    int find_file_in_dir (const char *path, const char *file)
    {
    struct dirent *entry;
    int ret = 1;
    DIR *dir;
    dir = opendir (path);
    errno = 0;
    while ((entry = readdir (dir)) != NULL) {
    if (strcmp(entry->d_name, file) == 0) {
    ret = 0;
    break;
    }
    }
    if (errno && !entry)
    perror ("readdir");
    closedir (dir);
    return ret;
    }