Q. How do I find out all large files in a directory?

A. There is no single command that can be used to list all large files. But, with the help of find command and shell pipes, you can easily list all large files.

Linux List All Large Files

To finds all files over 50,000KB (50MB+) in size and display their names, along with size, use following syntax:

Syntax for RedHat / CentOS / Fedora Linux

find {/path/to/directory/} -type f -size +{size-in-kb}k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
Search or find big files Linux (50MB) in current directory, enter:
$ find . -type f -size +50000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
Search in my /var/log directory:
# find /var/log -type f -size +100000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'

Syntax for Debian / Ubuntu Linux

find {/path/to/directory} -type f -size +{file-size-in-kb}k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'
Search in current directory:
$ find . -type f -size +10000k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'
Sample output:

./.kde/share/apps/akregator/Archive/http___blogs.msdn.com_MainFeed.aspx?Type=AllBlogs.mk4: 91M
./out/out.tar.gz: 828M
./.cache/tracker/file-meta.db: 101M
./ubuntu-8.04-desktop-i386.iso: 700M
./vivek/out/mp3/Eric: 230M

Above commands will lists files that are are greater than 10,000 kilobytes in size. To list all files in your home directory tree less than 500 bytes in size, type:
$ find $HOME -size -500b
OR
$ find ~ -size -500b

To list all files on the system whose size is exactly 20 512-byte blocks, type:
# find / -size 20

Perl hack: To display large files

Jonathan has contributed following perl code print out stars and the length of the stars show the usage of each folder / file from smallest to largest on the box:

 du -k | sort -n | perl -ne 'if ( /^(\d+)\s+(.*$)/){$l=log($1+.1);$m=int($l/log(1024)); printf  ("%6.1f\t%s\t%25s  %s\n",($1/(2**(10*$m))),(("K","M","G","T","P")[$m]),"*"x (1.5*$l),$2);}'

ls command: finding the largest files in a directory

You can also use ls command:
$ ls -lS
$ ls -lS | less
$ ls -lS | head +10

ls command: finding the smallest files in a directory

Use ls command as follows:
$ ls -lSr
$ ls -lSr | less
$ ls -lSr | tail -10

You can also use du command as pointed out georges in the comments.

However my favorite hack to above command is as follows:
# find / -type f -size +20000k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'

/var/log/kern.log: 22M
/sys/devices/pci0000:00/0000:00:02.0/resource0: 128M
/sys/devices/pci0000:00/0000:00:00.0/resource0: 256M
/opt/03Jun05/firefox-1.0.4-source.tar.bz2: 32M

Above command will find all files block size greater than 20000k and print filename followed by the file size. Output is more informative as compare to normal find command output

For example, to find files which are bigger than 4MB, use the following command:

$ find . -type f -size +4M

To find files smaller than 4MB, use this command:

$ find . -type f -size -4M

You might wonder how to find files between a certain size. For instance, you can find files between 30MB and 40MB using the following command:

$ find -size +30M -size -40M

To find files of exact size, for example 30MB, run:

$ find -size 30M