The Unix ls Command Sorted by Date

In the past, I've written
about using the sort
command to sort long
listings by date.

There's an easier way, I've
just learned.

The ls command has a
-t option. You
can use this to sort files by
timestamp.

It looks like this:

ls -t

If you wish to confirm that
the files are really being
sorted by date, you could
turn it into a long listing:

ls -lt

A long listing will not tell
you if files that are more
than 6 months old are in
precise date order to the
minute and to the second.

Here's yet another way to do
it:

ls -t --full-time

The above command will give a
long listing, but with the
modification time in hours,
minutes and seconds included.

Of course, it is the -t that
sorts the listing in timestamp
order.

I believe that the --full-time
option is of recent vintage. I don't
think we ever had it in the old days.

In fact, the only ls that I know
of that has a --full-time option
is GNU ls.

However, since I use Linux currently,
this is not a problem for me. I suspect
that the ls command under Linux is,
in most cases, GNU ls.

What's the lesson in all of this?
Orderliness and Godliness are related.
Commonplace things take on a Godly nature
when then are put into good order.

Just the other day, I used ls -t
on a directory of sub-directories. I was
trying to find the directory I had most
recently worked on. I could not find it.

I was so confused. What could possibly be
wrong? I thought maybe the ls -t was
broken.

Turned out I was logged into linux as
another user and had forgotten that fact.
I had forgotten I was logged into an
account other than my normal user account.

As it turns out, both user accounts have a directory
tree that is a mirror in terms of directory names but
not in terms of file content. However, to all
appearances, the name of the directory and the names
of the sub-directories are the same.

The confusion I felt had over the ls -t not
working later cleared up when I realized I was in
the wrong file hierarchy entirely.

This is what I mean by orderliness and Godliness being
related. A clear mental vision and a clear spiritual
vision often are the result of living an orderly life.

While the ls -t cannot order my entire life,
it can take the chaos out of a small corner of it.

Ed Abbott

The Unix du Command Under Linux

One of my favorite Linux commands
is the du command.

Here's an article:

The du Command

Why do I like the
du command?
Because it tells me
if I'm being a disk
hog. That's why.

Also, it helps me
to identify disk hog
directories.

As mentioned in the article,
there's a command that will
give you a summary on a specific
directory. Here it is:

du -hs

Note that you have to have permissions
on all the directories below this current
directory or you end up getting a lot of
goofy error messages.

Perhaps the quickest and easiest way to
get around the goofy error messages is
to login as root.

Note that the above command will only
give you one line of output.

Here's an input and output example:

$ du -hs mary
363M mary
$

Note that the final dollar sign is
my prompt coming back.

In this case, I'm being told that
the directory called mary
has used up 363 megabytes of
storage.

Ed Abbott

The Unix df Command Under Linux

One of the commands I use the
most frequently under Linux is
the df command.

df stands for disk
free. Basically, the
df command tells you
how much of your hard drive
has been used up.

This is very useful.

With df, you know whether
you have 50 percent of your hard
drive left for additional storage
or only 10 percent left.

Big difference.

Again, df means disk
free. This is exactly what
df tells you. How much
of the hard drive is free for
you to add other things to it.

Here's how to use the df
command:

df

Simple, isn't it?

Here some input and output:

$ df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/hda3            123079960  83666812  33161052  72% /
tmpfs                   518136         0    518136   0% /lib/init/rw
udev                     10240       672      9568   7% /dev
tmpfs                   518136         0    518136   0% /dev/shm
$

The final dollar sign is my prompt
coming back.

You can make the df command
quite a bit more useful by adding
the -h option to it.

The -h means human
readable. With -h, df
reports usage in megabytes
and gigabytes, and other units of
measure that are easy to digest.

Here's what df looks like with
-h present:

df -h

Here's a sample input and output for
df with the -h present:

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda3             118G   80G   32G  72% /
tmpfs                 506M     0  506M   0% /lib/init/rw
udev                   10M  672K  9.4M   7% /dev
tmpfs                 506M     0  506M   0% /dev/shm
$

Again, the final dollar sign
is my prompt coming back.
The initial dollar sign is the
prompt as it appears before
I've typed anything.

Note that df gives me 6
columns of information.

Perhaps the most important column
is the second column. This is the
size column.

This tells me, in megabytes or
gigabytes, how much space I have
left on my hard drive.

In my case, I have used up 80
gigabytes of storage and have
only 32 gigabytes left.

To see this, look at line one and
ignore the other lines.

Like many Unix commands, df
gives you more information that you
want initially.

Likely as not, the information you
will want from df is all on
the first line. At least, that's
true in this case.

Ed Abbott