find
find a file: find FROM_DIRECTORY -name 'FILE_NAME_OR_NAME_PATTERN'
find directories: find FROM_DIRECTORY -type d
find links: find FROM_DIRECTORY -type l
find exec: find FROM_DIRECTORY -type d -exec ls -l {} \; , here ; is escaping ; for ls command and {} is for every output of find this is input for the ls
find files that were modified in the past hour: find -mmin +60 -name 'FILE_NAME_OR_NAME_PATTERN'
find ... -iname ... : case insensitive search
-user USER: files owned by USER
-group GROUP: files owned by GROUP
-perm NNN: files has permission with NNN, here NNN is permission numbers like 666, 400, etc.
-size SIZE: files of size SIZE, e.g. +1M, 1M
-links NO_OF_LINKS: links associated with the file