Ls

ls (abbreviated from "List") is a command in Unix-like 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-like command line interface (CLI). Seeming like one of the most used Unix commands, it's appropriately loaded with available options.

Table of contents
1 History
2 Sample ls Search
3 Some ls command line options
4 Breakdown of output
5 Type column description
6 Permissions description

History

An ls utility first appeared in Version 5 AT&T UNIX. Today, two popular versions of ls include the Free Software Foundation's (part of the GNU coreutils package) and the one released by various BSD distributions, such as FreeBSD, OpenBSD, NetBSD, and Apple Computer's Darwin. Both are free software and open source.

Sample ls Search

Here is a sample display of its usage:

$ 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

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 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--,




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