BOL

The amount of databases we bioinformatician deal are just HUGE … In such cases, we always need to check our severe for free spaces etc. I planned this article to explains 2 simple commands that most bioinformatician want to know when they start using Linux / BioLinux. First: Size of a directory (du) and and second: free disk space that exists on your machine (df).

'du' – Check the size of a directory

$ du
This command ( du) gives you a list of directories that exist in the current working directory along with their sizes in kilobytes (default). The last line of the output gives you the total size of the current directory including its subdirectories.

$ du /home/jin1
The above command would give you the directory size of the directory /home/david

$ du -h
The same “du”command with some flag gives you a better output than the default one. The option '-h' stands for human readable format. Therefore, in order to print the sizes of the files / directories in your desire notation use this time suffixed with a 'k' if its kilobytes and 'M' if its Megabytes and 'G' if its Gigabytes.

$ du -ah
If you are interested in checking everything present in a folder use above mentioned command. It gives us not only the directories but also all the files that are present in the current directory. The “-a” flag displays the filenames along with the directory names in the output.

$ du -c
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 30M.

$ du -s
Use this command to displays a summary of the directory size. It is the simplest way to know the total size of the current directory.

$ du -S
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.

$ du --exculde=mp3
Several times it required to exclude some directory in our size calculation. In such cases 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.

'df' - finding the disk free space / disk usage

$ df
Hmmm … now “df” command is really useful, and I guess you are going to use it over time. Typing the above command, 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' for Gigabytes.

Example: Linux installed on /dev/hda1
$ df -h | grep /dev/hda1

All right, this is not the only option to check the sizes and free spaces but there are a few more options that can be used with 'du' and 'df' . I will discuss it later.