Linux系统编程之——实现ls-l命令
功能描述：
仿写ls -l的功能(编写myls_l程序),参数通过命令行传入:
1、获取当前工作目录路径并对该目录实现遍历。
2、仿ls -l以列表形式出当前工作目录下的所有文件(包括子目录)
需显示的文件属性。
知识要点
- ✓ Linux目录操作方法
– 打开目录、关闭目录- ✓ 读取目录文件
- ✓ Linux文件属性获取
- ✓ 文件属性解析相关的重要数据结构、函数、宏和文件掩码
源代码
/*************************************************************************
> File Name: myls.c
> Author: 张泽锋
> Mail: [email protected]
> Created Time: 2019年05月02日 星期四 20时13分38秒
> 功能描述：实现ls -l 命令的功能
************************************************************************/
#include 重要的函数原型与数据类型参考
/* //用到的函数原型
*
* char *getcwd(char *buf, size_t size); //获取当前目录
* int chdir(const char *path); //改变当前目录
* DIR *opendir(const char *name); //打开目录
* struct dirent *readdir(DIR *dirp); //读目录内容
* int closedir(DIR *dirp); //关闭目录
*
* int stat(const char *pathname, struct stat *statbuf); //获取文件信息
*
* struct passwd *getpwuid(uid_t uid); //获取用户信息
* struct group *getgrgid(gid_t gid); //获取用户组信息
*/
//用到的数据类型
#if 0
struct dirent
{
#ifndef __USE_FILE_OFFSET64
__ino_t d_ino;
__off_t d_off;
#else
__ino64_t d_ino;
__off64_t d_off;
#endif
unsigned short int d_reclen;
unsigned char d_type;
char d_name[256]; /* We must not include limits.h! */
};
struct stat {
unsigned long st_dev; /* Device. */
unsigned long st_ino; /* File serial number. */
unsigned int st_mode; /* File mode. */
unsigned int st_nlink; /* Link count. */
unsigned int st_uid; /* User ID of the file's owner. */
unsigned int st_gid; /* Group ID of the file's group. */
unsigned long st_rdev; /* Device number, if device. */
unsigned long __pad1;
long st_size; /* Size of file, in bytes. */
int st_blksize; /* Optimal block size for I/O. */
int __pad2;
long st_blocks; /* Number 512-byte blocks allocated. */
long st_atime; /* Time of last access. */
unsigned long st_atime_nsec;
long st_mtime; /* Time of last modification. */
unsigned long st_mtime_nsec;
long st_ctime; /* Time of last status change. */
unsigned long st_ctime_nsec;
unsigned int __unused4;
unsigned int __unused5;
};
/* A record in the user database. */
struct passwd
{
char *pw_name; /* Username. */
char *pw_passwd; /* Hashed passphrase, if shadow database
not in use (see shadow.h). */
__uid_t pw_uid; /* User ID. */
__gid_t pw_gid; /* Group ID. */
char *pw_gecos; /* Real name. */
char *pw_dir; /* Home directory. */
char *pw_shell; /* Shell program. */
};
/* The group structure. */
struct group
{
char *gr_name; /* Group name. */
char *gr_passwd; /* Password. */
__gid_t gr_gid; /* Group ID. */
char **gr_mem; /* Member list. */
};
struct timespec {
long ts_sec;
long ts_nsec;
};
//文件属性检测宏：
Because tests of the above form are common, additional macros are defined by POSIX to allow the test of the file type in st_mode to be
written more concisely:
S_ISREG(m) is it a regular file?
S_ISDIR(m) directory?
S_ISCHR(m) character device?
S_ISBLK(m) block device?
S_ISFIFO(m) FIFO (named pipe)?
S_ISLNK(m) symbolic link? (Not in POSIX.1-1996.)
S_ISSOCK(m) socket? (Not in POSIX.1-1996.)
The preceding code snippet could thus be rewritten as:
stat(pathname, &sb);
if (S_ISREG(sb.st_mode)) {
/* Handle regular file */
}
S_IRWXU 00700 owner has read, write, and execute permission
S_IRUSR 00400 owner has read permission
S_IWUSR 00200 owner has write permission
S_IXUSR 00100 owner has execute permission
S_IRWXG 00070 group has read, write, and execute permission
S_IRGRP 00040 group has read permission
S_IWGRP 00020 group has write permission
S_IXGRP 00010 group has execute permission
S_IRWXO 00007 others (not in group) have read, write, and
execute permission
S_IROTH 00004 others have read permission
S_IWOTH 00002 others have write permission
S_IXOTH 00001 others have execute permission
#endif