ls

-a, --all
do not ignore entries starting with .

-h, --human-readable
with -l and -s, print sizes like 1K 234M 2G etc

-l
use a long listing format

-r, --reverse
reverse order while sorting

-t
sort by time, newest first

-i
display inode number

tar

-c
create tarball

-f
specify tarball name

-p
preserve file permissions, default as root

-r
append files to the end of an existing uncompressed tarball

-t
list contents of an existing tarball

-u
append files to the end of an existing uncompressed tarball, if files are newer

-v
verbose

-x
extract tarball

-j
compress using bzip2

-z
compress using gzip

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)

display lines (-l), words (-w), bytes (-c), characters (-m) of file