Shell Programming and Scripting

Another option:

Code:

LC_ALL=C tr -dc '[:alnum:]' < /dev/random | fold -w1 | awk ' 
{
  if(/^[[:digit:]]$/) {
    if(n>=2)
      next
    n++
  }
  else {
    if(m>=6)
      next
    m++
  }
}
{
  s=s $1
} 
(n+m)==8 {
  exit
}
END { 
  print s
}'

Note I suggest using /dev/random here which may pause waiting for entropy but should give more random results...

Hi Scrutinizer,
I like your code better than mine. But if my dd was terminating on a SIGPIPE signal and generating an unwanted diagnostic for infernalhell, I don't see why the fold in your pipeline wouldn't suffer from the same fate.

Given that PIPE_BUF has a minimum allowed size of 512 bytes, using the following:

Code:

dd cbs=1 conv=unblock ibs=256 count=1

instead of:

Code:

fold -w1

might avoid the diagnostic message. But, of course, if 2 numeric characters and 6 alphabetic characters aren't found in the first 256 alphanumeric characters found in the data in /dev/random you won't get any output from your script. I would expect the likelihood of that happening being less than 3%.