Ls

ls (abbreviated from "LiSt") is a command in the Unix and Linux operating systems. It is similar to "dir" in DOS.

When executed, the ls command lists the contents of the current directory (or the given arguments) in the Unix/Linux command line interface (CLI). Seeming like one of the most used Unix commands, it's appropriately loaded with available options. Here is a sample display of its usage:

Sample ls Search

$ ls -laF
total 4
drwxr-xr-x   10 Brandon  None            0 Sep 30 16:48 ./
drwxr-xr-x   10 Brandon  None            0 Sep 30 16:48 ../
drwxr-xr-x    3 Brandon  None            0 Sep 30 19:02 bin/
-rw-r--r--    1 root     None           89 Dec 16 12:24 test
-rwxr-xr-x    1 Brandon  None           57 Sep 30 19:22 cygwin.bat*
-rw-r--r--    1 Brandon  None          766 Sep 30 19:22 cygwin.ico
drwxr-xr-x   15 Brandon  None            0 Sep 30 16:48 etc/
drwxr-xr-x    3 Brandon  None            0 Sep 30 19:27 home/
drwxr-xr-x   21 Brandon  None            0 Sep 30 19:02 lib/
drwxr-xr-x    2 Brandon  None            0 Sep 30 19:14 sbin/
-rw-r--r--    1 Brandon  None           22 Dec 16 12:24 testb3
drwxr-xr-x    3 Brandon  None            0 Sep 30 19:02 tmp/
drwxr-xr-x   20 Brandon  None            0 Sep 30 19:02 usr/
drwxr-xr-x    6 Brandon  None            0 Sep 30 19:02 var/

Some ls command line options

ls has a number of command line options, or "switches", that can modify the output. Some of these options are

• -F: adds a character that denotes the file's type, (/ for directories, * for executables, @ for links)
• -R: recursively lists contents in all subdirectories
• -l: long file format, including time, date, permissions and so on.
• -a: include dot and hidden files
• -f: unsorted output

Breakdown of output

The output given by ls in long listing form is broken into columns, as can be seen above. These columns can then be broken down to acquire information about listed files, directories and devices.

This is the tabular form of the first two listed items from the sample above with headings to explain each column:

Type	Permissions	Number of hard links	Owner	Group	Size	Date modified	Listing name
d	rwxr-xr-x	3	Brandon	None	0	Sep 30 19:02	bin/
-	rw-r--r--	1	root	None	89	Dec 16 12:24	test

Type column description

The very first character in a long listing gives the type of file.

Character	Type
-	Normal file
b	Block device
c	Character device
d	Directory
l	Symbolic link
p	Named pipe (FIFO)
s	Domain socket

Permissions description

example:

rwxr-xr--

The first three characters represent the owner's permissions on the item, the next three the the group's permissions, the last, everyone else.

Meaning of Characters by Character

As for the individual character meanings, the following is meant to explain that:

r - read permission;
w - write permission;
x - execute permission;
- - no permission;

Example

Given the output above, drwxr-xr--,

• This item is a directory;
• The file owner may read write and execute this item myself;
• The group this file belongs to may read and execute this file but not write to it;
• Everyone else may read this item but not write to it or execute it