Basic Commands

ls

-a do not ignore entries starting with .
-F append a symbol to indicate type (* executable, / directory, @ symlink, = socket, | named pipe, > door)
-h (with -l and -s) print sizes like 1K 234M 5G
-i display inode number
-l use a long listing format
-r reverse order while sorting
-s display size
-t sort by time, newest first

less & more

space / f scroll forward one screen
enter scroll forward one line
b scroll backward one screen
d scroll forward half a screen
h display help
q quit
/string search string forward
?string search string backward
n find next occurrence
N find previous occurrence (less only)

setfacl

-b remove all access acls
-d apply default acl
-k remove all default acls
-m set or modify acls
-n prevent automatic recalculation of mask
-R apply recursive
-x remove access acl

watch

Execute a command every X seconds (default 2).
watch -n X who execute the who command every X seconds

wc

Display lines (-l), words (-w), bytes (-c) or characters (-m) of file.

whatis

Display one-line man page description of a command.

whereis

Locate the binary, source and man pages for a command.

which

Locate a command.