The Unix ls Command

One of my all-time favorite
Unix commands is the ls command.

In its simplest form, ls looks
like this:

ls banana

The above lists a file named banana
if there is such a file.

Here's one that's more useful:

ls

This lists all the files in the current
directory.

OK. Here's something that could be even
more useful:

ls -l

This is the so-called long listing.
It lists eight columns of information on
every file in the current directory.

Included in the long listing is a time-stamp
for the file.

Note that a directory is just simply a
folder. Folders are directories and
directories are folders.

People who work on the command line
call them directories. People who
use a GUI (Graphical User Interface)
call them folders.

OK. Here's one that lists hidden files:

ls -A

The -A option means all.
That is to say, list all, both hidden
and non-hidden files.

Here's one that does a long listing on
all files, including hidden files:

ls -lA

Here's one that will look for subdirectories
inside of directories. Not only does it list
the current directory, it also lists anything
that belongs to the current directory:

ls -R

The -R suggests that the command is
recursive. It recursively descends into
directories finding sub-directories under
those directories going just as deep and
as far as it can.

Here's one that does a recursive long listing
on everything from the current directory on
down:

ls -lAR

Here's one that potentially looks at thousands
of files, listing those most recently modified
last:

ls -lAR | sort -k6

Use the above command to find a needle in a
haystack. The needle? A recently modified
file that is buried somewhere in listings of
thousands of files.

I love Unix commands because they are so simple.
Yet, you can do very complex things with them
when you start to string them together.

Ed Abbott