This blog post is dedicated to “rwman os” for contacting me to suggest that I was wrong !
And indeed I was !! ( <— two exclamation marks)
So this blog post create true random passwords has some mistakes and I am here to make amens.
the correct syntax on creating random passwords is this:
$ cat /dev/urandom | tr -dc $'\x21-\x7E' | head -c 21
and after further investigation (with GNU coreutils 8.23) seems that you can use octal as well:
$ cat /dev/urandom | tr -dc '\041-\176' | head -c 21