How to use ls command to list files in Linux? (code example)

The ls command is one of the basic commands that any Linux user should know; it is used to list information about files and directories in a file system. The following article will show you how to use the ls command in Linux. I hope it will be helpful to you.

How to use the ls command?

The syntax of the ls command is as follows:

ls [OPTIONS] [FILES]

The ls command has many [OPTIONS] options. Here are some commonly used options:

●　-l : You can make ls list files in long list format.

●　-a: Display all files and directories, including the following files.

●　-t: List the files in order of creation (modification) time.

●　-r: Display files in reverse order (originally in English alphabetical order).

●　-R: If there are files in the directory, the files in the directory will be listed in sequence.

When used without parameters, the ls command will list the names of all files in the current working directory in alphabetical order.

ls

Output:

cache  empty  games  lib  local  mail  opt  run

To list the files in a specific directory, you need to pass the path of the directory to the ls command. For example, to list the contents of the directory /etc, you would type:

ls /etc

You can also pass multiple directories and files to the ls command separated by spaces:

ls /etc /var /etc/passwd

If the logged-in user does not read permission to the directory, the user will receive a message stating that the ls command cannot open the directory:

ls /root

Output:

ls: cannot open directory '/root': Permission denied

How to list long List format?

The default output of the ls command only displays the name of the file, which is not very informative. However, when using the long list format, the ls command will display the following file information:

● File type

● File permissions

● Number of hard links to the file

● File owner

● File group

● File size

● Date and time

● File name

We can Use the -l (lowercase L) option to cause ls to output file information in a long listing format. For example:

ls -l /etc/hosts

Output:

-rw-r--r-- 1 root root 337 Oct  4 11:31 /etc/hosts

Explanation: Let us explain the output information

1. The first character '-' displays the file type

In our example, the first character is -, indicating a regular file. The values ​​for other file types are as follows:

● -: Regular files

● b: Block special files

● c: Character special files

● d : Directory

● l : Symbolic link

● n : Network file

● p : FIFO

● s : Socket

2. Nine characters (rw-r--r--) display file permissions

The first three characters are for users, the last three characters are for groups, and the last three characters are for others. We can use the chmod command to change file permissions; the permission characters can take the following values:

● r: permission to read the file

● w: permission to write the file

● x: Permission to execute the file

● s: Setgid bit

● t: Stickiness

In our example, rw-r--r-- represents the user The file can be read and written, while the group and others can only read the file. However, the number of nine characters (rw-r--r--) followed by 1 allows the number of characters following the hard link to the file.

3. root root 337

Two fields root root display the file owner and group, followed by the file size (337) in bytes. If you want to output the dimensions in a readable format, you need to use the -h option. Users can change file owners using the chmod command.

4, Oct 4 11:31

Oct 4 11:31 is the last modification date and time of the file.

5./etc/hosts

/etc/hosts is the name of the file.

How to display hidden files?

In Linux, hidden files are any files starting with a dot (.); and by default, the ls command will not display hidden files.

How to display all files, including hidden files, you need to use the -a option:

ls -la ~/

Output:

drwxr-x--- 10 linuxize  linuxize  4096 Feb 12 16:28 .
drwxr-xr-x 18 linuxize  linuxize  4096 Dec 26 09:21 ..
-rw-------  1 linuxize  linuxize  1630 Nov 18  2017 .bash_history
drwxr-xr-x  2 linuxize  linuxize  4096 Jul 20  2018  bin
drwxr-xr-x  2 linuxize  linuxize  4096 Jul 20  2018  Desktop
drwxr-xr-x  4 linuxize  linuxize  4096 Dec 12  2017 .npm
drwx------  2 linuxize  linuxize  4096 Mar  4  2018 .ssh

We also use the -l option to display all files details.

How to modify the ls output order?

By default, the ls command lists files in alphabetical order; but we can also modify the output order:

● --sort=extension (or -X) : Sort alphabetically by entry extension

● --sort=size (or -S): Sort by file size

● --sort=time (or -t): Sort by file size Modification time sorting

● --sort=version (or -v): Natural type (version) number in the text

If you want to get the results in reverse sort order, you need to use -r options.

For example, to sort the files in the /var directory by modification time in reverse sort order, you would use:

ls -ltr /var

It is worth mentioning that the ls command does not display the directory content occupation of total space.

How to list subdirectories recursively?

Use the -R option to tell the ls command to display the contents of the subdirectory:

ls -R

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