randout.sh :: readable random output from system kernel using /dev/urandom.

randout.sh

#!/usr/bin/env bash
#              bash 4.2.24(1)     Linux Ubuntu 12.04          Date : 2013-10-19
#
# _______________|  randout : readable random output from system kernel.
#
#           Usage:  randout  [bytes=512]  [--TYPE]  [characters/line]
#                   Types: space, graph, mime, url, alpha, alnum, alnoo, 
#                          lonum, hex, digit (see case below for details).
#
#        Examples:  #   Default type is --digit (but --hex is also available):
#                   $ randout 7
#                   9636770
#
#                   #   Types are generally named classes, however, e.g.:
#                   $ randout 10 --lonum
#                   91wkkxf838
#
#                   #   Third arg sets chars/line; otherwise all on one line:
#                   $ randout 35 --graph 10
#                   J6zk+2X]6_
#                   ^f%jY!l;:'
#                   BV2;SLIGt|
#                   +./9e
#                   
#
#    Dependencies:  /dev/urandom (non-blocking, unlike /dev/random)
#                   sed          (version which accepts \n on RHS of substitution)


#  CHANGE LOG  LATEST version available:   https://bitbucket.org/rsvp/gists/src
#
#  2013-10-19  Add url type, Base64 safe for URL and filename per RFC 4648.
#                 Re Base64: http://en.wikipedia.org/wiki/Base64
#  2013-10-18  Add alnoo type = alnum without O or o letters.
#                 Fix range to A-Z where necessary. Eliminate cat pipe; faster.
#  2013-10-11  Fix sed for one EOL per non-empty line. Add mime type.
#  2013-10-10  First version; for exposition, see
#              https://source.quora.com/Source-of-randomness-in-Linux-and-the-U-S-NIST
#              Wrote this because U.S. NIST Beacon was part of gov shutdown.


#           _____ PREAMBLE_v2: settings, variables, and error handling.
#
LC_ALL=POSIX
#      locale means "ASCII, US English, no special rules, 
#      output per ISO and RFC standards." 
#      Esp. use ASCII encoding for glob and sorting characters. 
shopt -s   extglob
#     ^set extended glob for pattern matching.
shopt -s   failglob
#         ^failed pattern matching signals error.
set -e
#   ^errors checked: immediate exit if a command has non-zero status. 
set -u
#   ^unassigned variables shall be errors.
#    Example of default VARIABLE ASSIGNMENT:  arg1=${1:-'foo'}


arg1=${1:-'64'}
#         ^number of output bytes.
arg2=${2:-'--digit'}
#         ^type of string
arg3=${3:-$arg1}
#         ^characters per line (PGP uses 64).


program=${0##*/}   #  similar to using basename
memf=$( mktemp /dev/shm/88_${program}_tmp.XXXXXXXXXX )


cleanup () {
     #  Delete temporary files, then optionally exit given status.
     local status=${1:-'0'}
     rm -f $memf
     [ $status = '-1' ] ||  exit $status      #  thus -1 prevents exit.
} #--------------------------------------------------------------------
warn () {
     #  Message with basename to stderr.          Usage: warn "message"
     echo -e "\n !!  ${program}: $1 "  >&2
} #--------------------------------------------------------------------
die () {
     #  Exit with status of most recent command or custom status, after
     #  cleanup and warn.      Usage: command || die "message" [status]
     local status=${2:-"$?"}
     cleanup -1  &&   warn "$1"  &&  exit $status
} #--------------------------------------------------------------------
trap "die 'SIG disruption, but cleanup finished.' 114" 1 2 3 15
#    Cleanup after INTERRUPT: 1=SIGHUP, 2=SIGINT, 3=SIGQUIT, 15=SIGTERM
#
# _______________     ::  BEGIN  Script ::::::::::::::::::::::::::::::::::::::::


#  #  2013-10-10  My one-liner for digit case explained. Case added later.
#  
#  cat /dev/urandom | strings --all | sed -e 's/[^0-9]//g' | tr -d '\n' \
#       | head --bytes=$arg1
#  
#  #  From /dev/urandom filter out everything except readable characters for sed 
#  #  which will then accept only digits, but tr is needed to remove line returns. 
#  #  Finally use head to limit the stream output to default 512 bytes.


#   This whole paragraph is actually an ONE-LINER...
strings --all  /dev/urandom                              \
| case "$arg2" in 
      '--space')  cat                                   ;;
                  #          ^Include space and TAB
      '--graph')  sed -e 's/[[:space:]]*//g'            ;;
                  #          ^Non-space characters
       '--mime')  sed -e 's/[^0-9A-Za-z+/]//g'          ;;
                  #          ^ALPHANUMERIC / + Base64
                  #           a.k.a. Radix-64 OpenPGP.
                  #           Padding char = not added.
        '--url')  sed -e 's/[^-0-9A-Za-z_]//g'          ;;
                  #          ^ALPHANUMERIC - _ Base64
                  #           Filename safe RFC 4648.
      '--alnum')  sed -e 's/[^0-9A-Za-z]//g'            ;;
                  #          ^ALPHANUMERIC
      '--alnoo')  sed -e 's/[^0-9A-NP-Za-np-z]//g'      ;;
                  #          ^ALPHANUMERIC less O & o
                  #           thus zero is distinctive.
      '--alpha')  sed -e 's/[^A-Za-z]//g'               ;;
                  #          ^ALPHA characters only
      '--lonum')  sed -e 's/[^0-9a-z]//g'               ;;
                  #          ^Lower case w/ numbers
        '--hex')  sed -e 's/[^0-9A-F]//g'               ;;
                  #          ^HEX
      '--digit')  sed -e 's/[^0-9]//g'                  ;;
                  #          ^DIGITS only.
              *)  die "undefined arg: $arg2"  113       ;;
esac                                                     \
|  tr -d '\n'  |  head --bytes=$arg1                     \
|  sed -e "s/.\{$arg3\}/&\n/g"  -e 's/$/\n/'             \
|  sed -e '/^$/d'
     #  First part of sed break up the stream into lines
     #  of fixed length given by arg3. The second part
     #  insures that the stream always ends with EOL.
     #  The final sed is needed to re-read the stream, 
     #  then delete any blank lines for consistent output, 
     #  i.e. a line always ends with EOL.


cleanup
# _______________ EOS ::  END of Script ::::::::::::::::::::::::::::::::::::::::

#  vim: set fileencoding=utf-8 ff=unix tw=78 ai syn=sh :