ls (abbreviated from "list") is a command in Unix-like operating systems. It is similar to " dir" in DOS. In most modern Unix variants, the dir command is also available, but it is simply another way of invoking the ls program.
When executed, the ls command lists the contents of the current directory (or the given arguments). It is a basic utility of the Unix-like command line interface (CLI). As one of the oldest and most popular Unix commands, it has acquired a vast number of options. Modern ls implementations, such as GNU ls, can produce colored output according to customizable configuration files.
1 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 softwareThis article refers to free software as defined by the Free Software Foundation. For software available free of charge, see Freeware. The term free software refers to software which, once obtained, can be used, copied, studied, modified and redistributed. and open sourceNote: "open source" in the intelligence community simply means "any information accessible to the public, possibly after paying a fee". This article is about open source software, a more common meaning for the term "open source". Open source or open sourc.
2 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/
3 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 symlinks)
-R: recursivelyIn mathematics and computer science, recursion is a particular way of specifying (or constructing) a class of objects (or an object from a certain class) with the help of a reference to other objects of the class: a recursive definition defines objects in lists contents in all subdirectories
-l: long file format, including time, date, permissions and so on.
-a: do not hide entries starting with a dot
-f: unsorted output
4 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 |
