ls
ls
(think list) is one of the most-used commands in Unix-like operating systems. ls
prints the files and sub-directories located in the current working directory, or, in the directory specified as an argument by the user.
ls
is incredibly useful for navigation. When working with a graphical user interface (GUI), like Finder in MacOS or File Explorer in Windows, the files and folders in a directory are shown to you each time you navigate to and from a specific directory.
When navigating files and folders via a shell, this is not quite as straightforward. When using cd
to navigate to a particular directory, you will not have a nice list of files and folders presented to you upon navigating to said directory. Instead, we use ls
to list the files and folders, and see what options we have for navigation. For example, let’s say our current working directory is /home/john/
, and we want to go to our projects folder (/home/john/projects
) to see what projects we have. To navigate to our projects folder, we can use cd
.
cd projects
bash
Unfortunately, cd
will simply change your current working directory, and that is all that will happen. How do you know what projects reside in our projects folder? Well, we can use ls
to list the files and folders in our projects folder.
ls
bash
project_1 project_2 project_3 project_4 readme.txt
Now, we know we can use cd
to navigate to any of the following project folders: project_1
, project_2
, project_3
, and project_4
. Let’s navigate to our project_1
folder, and list the files and folders in our project_1
folder.
cd project_1
ls
bash
This would result in an output that looks something like this.
schedule.pdf code.py STAT_190 MA_165
bash
Here you can see that there are two files, and two sub-directories located in the project_1
directory. From here, you can cd
into the STAT_190
or the MA_165
sub-directory.
ls
and cd
are often used hand-in-hand. This makes sense: it is unlikely that you will remember the files located in each directory and sub-directory when navigating in the terminal.
options
Like most unix utilities, there are many options that are used with ls
. The following is an example of using ls
with the -a
option.
ls -a
bash
Here are a few, and what they do!
-
-a
: list all files, including hidden files. -
-l
: outputs the files in the directory in a list format. -
-S
: sorts the output by the size of each file (please note that this is a capital S). -
-h
: stands for "human-readable" and outputs the size of each file in a human-readable format. -
-R
: recursively lists files in the current directory and (recursively) in all subdirectories, including child directories, grandchild directories, etc. -
-d
: limits the output to the directories themselves, and does not show the contents inside the directories
Multiple options can be given 1-by-1, like in the following example.
ls -a -l
# order of options does not matter
ls -l -a
bash
Or, rather than providing a new dash for each option, you can "smash" every option together.
ls -la
# order still doesn't matter
ls -al
bash
Dr Ward usually uses ls -la
, which lists all files (including hidden files) and outputs the files in the directory in a list format.
For instance, in the directory /anvil/projects/tdm/data/fars
if we type: ls -la
we get the following results:
x-mdw@login04.anvil:[fars] $ ls -la total 32849 drwxrwsr-x+ 49 x-kamstut x-tdm-admin 16384 Jul 30 05:28 . drwxrwsr-x+ 55 x-kamstut x-tdm-admin 4096 Jul 29 17:29 .. drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:15 1975 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1976 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1977 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1978 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1979 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1980 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1981 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1982 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1983 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1984 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1985 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1986 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1987 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1988 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1989 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1990 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1991 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1992 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1993 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1994 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1995 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1996 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1997 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1998 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 1999 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2000 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2001 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2002 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2003 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2004 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2005 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2006 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2007 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2008 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2009 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2010 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2011 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2012 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2013 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2014 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2015 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2016 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2017 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2018 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2019 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2020 drwxrwsr-x+ 2 x-mdw x-tdm-admin 4096 Jul 30 05:14 2021 -rw-r--r-- 1 x-mdw x-tdm-admin 33397890 Jul 30 05:28 7581.csv -rwxrwxr-x 1 x-kamstut x-tdm-admin 720 Jul 23 2020 states.csv
bash
We see that there is one directory for each year from 1975 to 2021, and a file called 7581.csv
and a file called states.csv
.
Each line describes the permissions of a file or directory, the number of hard links to the file or directory, the owner of the file or directory, the UNIX group associated with that file or directory, the number of bytes, the date of the last modification, and the names of the file or directory.
To see the recursive file listing in practice, you might (for instance) look at the AirBnB directory recursively:
ls -R /anvil/projects/tdm/data/airbnb
As another example, compare the output from:
ls /anvil/projects/tdm/data/airbnb/*
which shows all of the contents in the (first level of) the airbnb
directory, and the contents of each such directory
as opposed to:
ls -d /anvil/projects/tdm/data/airbnb/*
which only shows the contents in the airbnb
directory but does NOT show the contents in any such directories. The behavior of -d
is described in the man
pages for ls
as: "Directories are listed as plain files (not searched recursively)"