Shell - Read binary file character by character as hex

Question

I'm trying to read serial input(/dev/tty*) character by character. I need this to parse the data following the corresponding protocol. My current method is as follows:

while read -rs -n 1 c; do
    echo Read a char:
    echo ${c}
done < "${SERIAL_PORT}"

This works, except for the fact that the data is binary and some bytes are \x00, which is not allowed as a character in a variable. My aim is to first convert the byte into a hex string(two characters) which I will then store in the variable. This is where I get stuck. What is a good way to do this? I would prefer to stay posix compliant.

Answer 1

Using od to create hexadecimal ASCII representation for each byte/character of input, and outputting these one at a time:

od -v -An -txC <input |
awk '{ for (i = 1; i <= NF; ++i) print $i }'

This will output one hexadecimal number per line.

You may then read this with read if you wish, but it would be better if you could do your processing inside of the already existing awk code.