Password generation script

pw

#!/bin/sh

set -e

# generate allowed_characters number_of_characters
generate()
{
 cat /dev/random | env LC_CTYPE=C tr -cd $1 | head -c $2
}

usage()
{
 echo "Usage: pw 16 [lim|num|alpha|dice|ware]"
 exit 1
}

get_line()
{
 awk '/'$1'/{ print NR; exit }' $DICE_WARE_LIST
}

get_word()
{
 awk 'NR=='$1'' $DICE_WARE_LIST
}

copied()
{
 echo "Password copied to clipboard"
}

if [[ "$#" -lt 1 ]]
then
 usage
fi

if [[ "$#" -gt 2 ]]
then
 usage
fi

if expr "$1" : '-\?[0-9]\+$' >/dev/null; then
 echo "Unknown error in argument"
 usage
fi

if [ $1 -gt 65535 ]; then
 echo "Requested string is too large"
 usage
fi

if [ "$#" -gt 1 ]
then
 if [ "$2" != "lim" ] && [ "$2" != "num" ] && [ "$2" != "alpha" ] && [ "$2" != "dice" ] && [ "$2" != "ware" ]
 then
   echo "Unrecognized second parameter"
   usage
 fi
fi

if [ "$#" -gt 1 ]
then
 if [ "$2" = "lim" ]
 then
   generate 'a-z0-9' $1 | pbcopy
   copied
 elif [ "$2" = "num" ]
 then
   generate '0-9' $1 | xargs echo
 elif [ "$2" = "alpha" ]
 then
   generate 'a-z' $1 | xargs echo
 elif [ "$2" = "dice" ]
 then
   generate '1-6' $1 | xargs echo
 elif [ "$2" = "ware" ]
 then
   # todo: download https://www.eff.org/files/2016/07/18/eff_large_wordlist.txt somehow
   if [ -z "$DICE_WARE_LIST" ]
   then
     echo "Please set DICE_WARE_LIST to the location of your diceware text file."
     exit 1
   fi

   RESULT=""

   for i in `seq 1 $1`
   do
     NUM=`generate '1-6' 5`
     LINE=`get_line $NUM`
     WORD=`get_word $LINE`
     SPLIT=(${WORD// / })
     RESULT="$RESULT ${SPLIT[1]}"
   done

   echo $RESULT
 fi
else
 generate 'a-zA-Z0-9`~!@#$%^&*()_+-={}[]|;<,>.?/' $1 | pbcopy
 copied
fi