hex string to binary

echo -ne '\x5a'

echo -n 5a | perl -pe 's/([0-9a-fA-F]{2})/chr hex $1/gie'

echo 5a | perl -ne 's/([0-9a-fA-F]{2})/print chr hex $1/gie'

perl -lne 'print pack "H*", $_'

echo -n 5a | sed 's/\([0-9A-F]\{2\}\)/\\\\\\x\1/gI' | xargs printf

echo -n 5a | xxd -r -p

$ a=5a
$ printf "\x${a}"

參考來源：

1. linux shell scripting: hex string to bytes
2. Shell Script 文章