Convert binary data to hexadecimal in a shell script

With od (GNU systems):

$ echo abc | od -A n -v -t x1 | tr -d ' \n'
6162630a

With hexdump (BSD systems):

$ echo abc | hexdump -ve '/1 "%02x"'
6162630a

From Hex dump, od and hexdump:

"Depending on your system type, either or both of these two utilities will be available--BSD systems deprecate od for hexdump, GNU systems the reverse."

Perhaps use xxd:

% xxd -l 16 -p /dev/random
193f6c54814f0576bc27d51ab39081dc

Watch out!

hexdump and xxd give the results in a different endianness!

$ echo -n $'\x12\x34' | xxd -p
1234
$ echo -n $'\x12\x34' | hexdump -e '"%x"'
3412

Simply explained. Big-endian vs. little-endian :D