<b_jonas> slashlearn block device/Block devices are a concession made in Unix to make raw hard disks and magnetic tape have a similar interface to regular files and terminals. Since magnetic tapes can\'t write individual bytes, only entire blocks, the interface isn\'t exactly the same, thus the dreaded dd obs= option was born.

tr -dc "AB,.<>+-"</dev/urandom|fold -w"${1-50}"|sed -n ":a;s/A\([^B]*\)B/[\1]/;ta;/[AB]/b;p;q"