Finding files with the find command is actually more difficult than it should be.
This finds and lists the largest files (more than 200 MB) on the whole file system:
find / -type f -size +200000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
The same, but simpler syntax:
find / -size +200M -ls
This finds the most recently changed files under the current directory:
find . -type f -printf '%TY-%Tm-%Td %TT %p\n' | sort
In order to search a specific directory (path_to_directory) and all its subdirectories (-r for recursive) for files that contain a specific text string, use the following command:
grep -r "textstring" path_to_directory
grep (case-insensitive, recursive) grep doesn't offer any possibility to recursively descent down the directory tree. The following command searches e.g. just thru all the files in the current directory:
grep bacteria *
To make the search case-insensitive, one can use the i flag:
grep -i bacteria *
But if you want to do a recursive search you have to use a quite complicated construction of UNIX commands to achieve this goal:
find ~/Mail -type f -exec grep 'bacteria' {} \; -print