lec6vid3Getopts

#!/bin/bash

# this script generates a random password 
# this user can set the password length with -l and a special character with -s
# verbose mode can be enabled with -v

usage(){
   echo "usage: ${0} [-vs] [-l length] " >&2
   echo "generate a random password"
   echo " -l length  specify the password length"
   echo " -s         append a special character to the password"
   echo " -v         increase verbosity"
   exit 1
}

# set default password length 
LENGTH=48

while getopts vl:s OPTION # vls because we are providing vls option , l: means l must have a argument on its own
do
  case ${OPTION} in
  v) 
    VERBOSE='true'
    echo 'verbose mode on'
    ;;
  l)
    LENGTH="${OPTARG}"
    ;;
  s)
    USE_SPECIAL_CHARACTER=true
    ;;
  ?)
    usage
    ;;
  esac
done     

# generaing password 
echo "Generating password"
PASSWORD=$(date +%s%N$RANDOM | sha256sum | head -c${LENGTH})

# append a special character if requested to do so 
if [ "${USE_SPECIAL_CHARACTER}" = 'true' ]
then
   echo 'selecting a radom special charater'
   SPECIAL_CHARACTER=$( echo '!@$%&()' | fold -w1 | shuf | head -c1 )
   PASSWORD=$PASSWORD$SPECIAL_CHARACTER
fi

echo "DONE PASSWORD: ${PASSWORD}"
exit 0