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The content of this article mainly focuses on how to tell the linux ll command. The content of the article is clear and well-organized. It is very suitable for beginners to learn and is worth reading. Interested friends can follow the editor to read together. I hope you can get something through this article!

1. Ll command

Ll is not a basic command under linux, it's actually an alias for ls-l.

Ubuntu does not support the command ll by default, and you must use ls-l, which is not very convenient to use.

If you want to use this command, you can make the following modifications:

Open ~ / .bashrc

Find the # alias ll='ls-lump and remove the preceding #. (close the original terminal for the command to take effect)

In this way, individual users can use the ll command, and when switching to superuser, the prompt cannot find the command when using the ll command, that is because you only modify the configuration of the individual user, so the problem can be solved by switching to root and doing the same operation.

Revelation: we can add any other command aliases by modifying ~ / .bashrc.

2. The result of the ll command

Drwxr-xr-x 2 root root 48 2013-11-27 16:34 test/

The first field represents the properties of the file. Linux files are basically divided into three attributes: readable (r), writable (w), and executable (x).

Here are ten squares to add (when the program is implemented, it is actually ten bit bits).

The first letter indicates the file type

"-", an ordinary document. The "d" directory, the letter "d", is the abbreviation of dirtectory (directory). "l" symbolic link. Please note that a directory or folder is a special file, which contains information about other files and folders. "b" block device file. The "c" character device file.

The following three characters are divided into three groups, each indicating the read, write and execution permissions of this file, for owner, group, and others.

Because Linux is a multi-user and multi-tasking system, a file may be used by many people at the same time, so we must set the permissions for each file. The permission locations of the files are arranged in the following order (take-rwxr-xr-x as an example):

Rwx (Owner) rMurx (Group) rMurx (Other)

The permissions shown in this example are: users themselves can read, write, and execute; the same group of users can read, not write, and execute; other users can read, not write, and execute.

In addition, the execution part of some program attributes is not X, but S, which means that the user who executes the program can temporarily have the same authority as the owner to execute the program. It generally appears in instructions or programs such as system management, which allow users to have the identity of root when they execute them.

The second field represents the number of files. If it is a file, then this number is naturally 1, if it is a directory, then its number is the number of files in that directory.

The third field represents the owner of the file or directory. If the user is currently on his or her own Home, then this column is probably full of its account name.

The fourth field indicates the group to which it belongs (group). Each user can have more than one group, but most users should belong to only one group, and only when the system administrator wants to give special permissions to a user will he be given another group.

The fifth field indicates the file size. The file size is represented by byte, while the empty directory is generally 1024byte, of course, you can use other parameters to make the file display in different units, such as using ls-k is to use kb to show the size of a file, but generally we still give priority to byte.

The sixth field indicates the time of the last modification. Expressed in the format "month, day, time", for example, 5:46 on Aug 15 means 5:46 in the morning on August 15th.

The seventh field represents the file name. We can use ls-a to show hidden file names.

Use the chmod command to modify file permissions

What is Linux system Linux is a free-to-use and free-spread UNIX-like operating system, is a POSIX-based multi-user, multi-task, multi-threaded and multi-CPU operating system, using Linux can run major Unix tools, applications and network protocols.

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