@ author: Charles Hau @ date: Thu 3 Oct 2019 19:51:38 EDT
Download the source code. In the home folder of the project(also where Makefile located), run make A to compile, where A is one of these: cat cp diff ls mv rm stat
The binary file will be stored in /bin. I also put some sample files and directories for test. The source code is in src/source and src/header
Run ./myA to run the command, where A is same thing above.
All the programs has been run on Linux raspberry 4.19.0-6-686 #1 SMP Debian 4.19.67-2+deb10u1 (2019-09-20) i686 GNU/Linux, with compiler g++ 8.3.0.
Feel free to email me and have fun!
The key point of this program, is to encapsulate a buildin file management kit into a class called File.
The properties of File is mainly from stat():
struct stat {
dev_t st_dev; /* ID of device containing file */
ino_t st_ino; /* inode number */
mode_t st_mode; /* file type and mode */
nlink_t st_nlink; /* number of hard links */
uid_t st_uid; /* user ID of owner */
gid_t st_gid; /* group ID of owner */
dev_t st_rdev; /* device ID (if special file) */
off_t st_size; /* total size, in bytes */
blksize_t st_blksize; /* blocksize for filesystem I/O */
blkcnt_t st_blocks; /* number of 512B blocks allocated */
/* Since Linux 2.6, the kernel supports nanosecond
precision for the following timestamp fields.
For the details before Linux 2.6, see NOTES. */
struct timespec st_atim; /* time of last access */
struct timespec st_mtim; /* time of last modification */
struct timespec st_ctim; /* time of last status change */
#define st_atime st_atim.tv_sec /* Backward compatibility */
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
};(reference: https://manpages.debian.org/stretch/manpages-dev/stat.2.en.html)
About mode_t and how to check file type, see Appendix I
Besides, struct passwd and struct group are also used.
struct group {
char *gr_name; /* group name */
char *gr_passwd; /* group password */
gid_t gr_gid; /* group ID */
char **gr_mem; /* NULL-terminated array of pointers
to names of group members */
};
struct passwd {
char *pw_name; // username
char *pw_passwd; // user password
uid_t pw_uid; // user ID
gid_t pw_gid; // group ID
char *pw_gecos; // user information
char *pw_dir; // home directory
char *pw_shell; // shell program
};
(reference https://manpages.debian.org/stretch/manpages-dev/getpwuid.3.en.html)
In the program, we mainly use passwd getpwuid(st_uid) and group getgrgid(st_gid) to get user's group and owner.
- Firstly use type
bitset, transfer from int to binary, then to string. - Then use function
string to_rwx(int)switch to string.
std::bitset<9> res (sb.st_mode); // new a bitset res
string s_res = res.to_string('-','*'));
to_rwx(s_res)A string with formatted date.
ctime(&sb.st_atime)
ctime is a classical function from time.h, which take const *t_time as a param and return a string
Also, st_atime is from
#define st_atime st_atim.tv_sec and tv_sec actually is t_time
The Status Change Time and Modification Time is the same principle
print the error, with the format
pre-information, error number, error information
If a file is a context, read from it and return a string storing it.
It will have two errors: 1. size; 2. existence;
The instance variable children is made by pair<File, string>
The second string store a brief name of a file. Because in File.name, you have to store the whole path, so, in case of ls, it could be super inconvenient.
In File.expand(), we use two builtin class, dirent and DIR, referring to files and directories in file system.
What's noticeable is, in File.expand(), the File.name keeps increasing, from /f to /f/ff to /f/ff/fff, but we always keep its original name fff in pair<File, string>.
I use three versions of dump here. It will copy from a file, and store it in file or stream or char buffer.
There is bunches of system types built-in. It will mainly be used in class and myls.
S_IFMT 0170000 bit mask for the file type bit field
S_IFSOCK 0140000 socket
S_IFLNK 0120000 symbolic link
S_IFREG 0100000 regular file
S_IFBLK 0060000 block device
S_IFDIR 0040000 directory
S_IFCHR 0020000 character device
S_IFIFO 0010000 FIFO
Compare the above things with st_mode is illegal. You have to call those functions:
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.)