article explains 2 simple commands that most people want to
know when they start using Linux. They are finding the size
of a directory and finding the amount of free disk space that
exists on your machine. The command you would use to find the
directory size is ' du '. And to find the free disk space
you could use ' df '.
All the information present in this article is available in
the man pages for du and df. In case you get bored reading the
man pages and you want to get your work done quickly, then this
article is for you.
'du' - Finding the size of a directory
Typing the above at the prompt gives you a list of directories
that exist in the current directory along with their sizes.
The last line of the output gives you the total size of the
current directory including its subdirectories. The size given
includes the sizes of the files and the directories that exist
in the current directory as well as all of its subdirectories.
Note that by default the sizes given are in kilobytes.
The above command would give you the directory size of the directory
$ du -h
This command gives you a better output than the default one.
The option '-h' stands for human readable format. So
the sizes of the files / directories are this time suffixed
with a 'k' if its kilobytes and 'M' if its Megabytes and 'G'
if its Gigabytes.
$ du -ah
This command would display in its output, not only the directories
but also all the files that are present in the current directory.
Note that 'du' always counts all files and directories while
giving the final size in the last line. But the '-a' displays
the filenames along with the directory names in the output.
'-h' is once again human readable format.
This gives you a grand total as the last line of the
output. So if your directory occupies 30MB the last 2 lines
of the output would be
The first line would be the default last line of the 'du' output
indicating the total size of the directory and another line
displaying the same size, followed by the string 'total'.
This is helpful in case you this command along with the grep
command to only display the final total size of a directory
as shown below.
$ du -ch | grep total
This would have only one line in its output that displays the
total size of the current directory including all the subdirectories.
Note : In case you are not familiar with
pipes (which makes the above command possible) refer to Article
No. 24 . Also grep is one of the most important commands
in Unix. Refer to Article No. 25 to know
more about grep.
$ du -s
This displays a summary of the directory size. It is the simplest
way to know the total size of the current directory.
This would display the size of the current directory excluding
the size of the subdirectories that exist within that directory.
So it basically shows you the total size of all the files
that exist in the current directory.
The above command would display the size of the current directory
along with all its subdirectories, but it would
exclude all the files having the given pattern present in their
filenames. Thus in the above case if there happens to be any
mp3 files within the current directory or any of its subdirectories,
their size would not be included while calculating the
total directory size.
'df' - finding the disk free space / disk usage
Typing the above, outputs a table consisting of 6 columns. All
the columns are very easy to understand. Remember that the 'Size',
'Used' and 'Avail' columns use kilobytes as the unit. The 'Use%'
column shows the usage as a percentage which is also very useful.
$ df -h
Displays the same output as the previous command but the '-h'
indicates human readable format. Hence instead of kilobytes
as the unit the output would have 'M' for Megabytes and 'G'
Most of the users don't use the other parameters that can be
passed to 'df'. So I shall not be discussing them.
I shall in turn show you an example that I use on my machine.
I have actually stored this as a script named 'usage'
since I use it often.
I have my Linux installed on /dev/hda1 and I have mounted my
Windows partitions as well (by default every time Linux boots).
So 'df' by default shows me the disk usage of my Linux as well
as Windows partitions. And I am only interested in the disk
usage of the Linux partitions. This is what I use :
$ df -h | grep /dev/hda1 | cut -c 41-43
This command displays the following on my machine
Basically this command makes 'df' display the disk usages of
all the partitions and then extracts the lines with /dev/hda1
since I am only interested in that. Then it cuts the characters
from the 41st to the 43rd column since they are the columns
that display the usage in % , which is what I want.
Note : In case you are not familiar with pipes (which
is used in the above command) then refer to Article
No. 24 . 'cut' is another tool available in Unix. The above
usage of cut gets the the characters that are present in the
specified columns. If you are interested in knowing how to mount
you Windows partitions under Linux, please refer to Article
No. 3 .
are a few more options that can be used with 'du' and 'df' .
You could find them in the man pages.