How To Get The Size Of A Directory.
When listing the contents of a directory using the ls command, you may have noticed that the size of the directories is almost always 4096 bytes (4 KB). That’s the size of space on the disk that is used to store the meta-information for the directory, not what it contains.
The command you’ll want to use to get the actual size of a directory is du, which is short for “disk usage”.
Getting the Size of a Directory
The du command displays the amount of file space used by the specified files or directories. If the specified path is a directory, du summarizes disk usage of each subdirectory in that directory. If no path is specified, du reports the disk usage of the current working directory .
When invoked without any options, du displays the disk usage of the given directory and each of its subdirectories in bytes.
Typically, you would want to display the space occupied by the directory in a human-readable format. For example, to get the total size of the /var directory, you would run the following command:
sudo du -sh /var
The output will look something like this:
85G /var
Let’s explain the command and its arguments:
The command starts with sudo because most of the files and directories inside the /var directory are owned by the root user and are not readable by the regular users. If you omit sudo the du command will print “du: cannot read directory”.
s – Display only the total size of the specified directory, do not display file size totals for subdirectories.
h – Print sizes in a human-readable format (h).
/var – The path to the directory you want to get the size.
What if you want to display the disk usage of the first-level subdirectories? You have two options. The first one is to use the asterisk symbol (*) as shown below, which means “match everything that doesn’t start with a period (.)”. The -c option tells du to print a grand total of all sizes:
sudo du -shc /var/*
24K /var/db 4.0K /var/empty 4.0K /var/games 77G /var/lib 4.0K /var/local 0 /var/lock 3.3G /var/log 0 /var/mail 4.0K /var/opt 0 /var/run 196K /var/spool 28K /var/tmp 85G total
Another way to get a report about the disk usage of the first-level subdirectories is to use the –max-depth option:
sudo du -h --max-depth=1 /var
77G /var/lib 24K /var/db 4.0K /var/empty 4.0K /var/local 4.0K /var/opt 196K /var/spool 4.0K /var/games 3.3G /var/log 5.0G /var/cache 28K /var/tmp 85G /var 85G total
By default, the du command shows the disk space used by the directory or file. To find the apparent size of a directory, use the –apparent-size option. The “apparent size” of a file is how much data is actually in the file.
sudo du -sh --apparent-size /var
When you transfer a directory via SCP , Rsync ., or SFTP the amount of data that is transferred over the network is the apparent size of the files. This is why the size of space on the disk used on the source when displayed with du (without –apparent-size) is not the same as the size on the target.
The du command can also be combined with other commands with pipes.
For example, to print the 5 largest directories within the /var directory, you would pipe the output of du to the sort command to sort the directories by their size and then pipe the output to the head command that will print only the top 5 directories:
sudo du -h /var/ | sort -rh | head -5
85G /var/ 77G /var/lib 75G /var/lib/libvirt/images 75G /var/lib/libvirt 5.0G /var/cache/pacman/pkg
Conclusion
In Linux, you can get the size of a directory using the du command.
