hexdump - basics

# hex bytes
% echo hello | hexdump -v -e '/1 "%02X "' ; echo
68 65 6C 6C 6F 0A 

# same, with ASCII section
% echo hello | hexdump -e '8/1 "%02X ""\t"" "' -e '8/1 "%c""\n"'
68 65 6C 6C 6F 0A        hello

# hex with preceding 'x'
% echo hello | hexdump -v -e '"x" 1/1 "%02X" " "' ; echo
x68 x65 x6C x6C x6F x0A 

# one hex byte per line
% echo hello | hexdump -v -e '/1 "%02X\n"' 
68
65
6C
6C
6F
0A

# a table of byte#, hex, decimal, octal, ASCII
% echo hello | hexdump -v  -e '/1  "%_ad#    "' -e '/1    "%02X hex"' -e '/1 " = %03i dec"' -e '/1 " = %03o oct"' -e '/1 " = _%c\_\n"'
0#    68 hex = 104 dec = 150 oct = _h_
1#    65 hex = 101 dec = 145 oct = _e_
2#    6C hex = 108 dec = 154 oct = _l_
3#    6C hex = 108 dec = 154 oct = _l_
4#    6F hex = 111 dec = 157 oct = _o_
5#    0A hex = 010 dec = 012 oct = _
_

# byte# & ASCII with control chars
% echo hello | hexdump -v  -e '/1  "%_ad#  "' -e '/1 " _%_u\_\n"'
0#   _h_
1#   _e_
2#   _l_
3#   _l_
4#   _o_
5#   _lf_

Source: https://www.commandlinux.com/man-page/man1/hexdump.1.html