Shell Programming and Scripting

find . -type f |while read file
do
  suffix=${file##*.}
  low=$(echo $suffix |tr '[A-Z]' '[a-z]')
  if [[ "$low" == "zip" ]]; then
      unzip $file
  fi
  if [[ "$low" == "gpg" ]]; then
      gpg $file
  fi
done

for file in `ls | xargs`
do
extn=`echo "$file" | awk '{printf ("%-3s",$1)}' | tr '[A-Z]' '[a-z]'`
if [ "$extn" = "zip" ] ; then
    unzip "$file"
elif [ "$extn" = "gpg" ] ; then
     gpg "$file"
else
     echo "Unknown filetype"
fi
done

decrypt(){
  case $1 in 
    *.[zZ][iI][pP]) unzip "$1" ;;
    *.[gG][pP][gG]) gpg "$1" ;;
  esac
}

decrypt abc.zIp

decrypt(){
  case ${1,,} in 
    *.zip) unzip "$1" ;;
    *.gpg) gpg "$1" ;;
    *) echo "Unknown filetype" ;;
  esac
}

${parameter^pattern}
${parameter^^pattern}
${parameter,pattern}
${parameter,,pattern}
       Case  modification.   This  expansion modifies the case of alphabetic characters in parameter.  The pattern is expanded to
       produce a pattern just as in pathname expansion.  The ^ operator converts lowercase letters matching pattern to uppercase;
       the  , operator converts matching uppercase letters to lowercase.  The ^^ and ,, expansions convert each matched character
       in the expanded value; the ^ and , expansions match and convert only the first character in the expanded value..  If  pat‐
       tern  is  omitted,  it  is treated like a ?, which matches every character.  if parameter is @ or *, the case modification
       operation is applied to each positional parameter in turn, and the expansion is the resultant list.  If  parameter  is  an
       array  variable  subscripted  with @ or *, the case modification operation is applied to each member of the array in turn,
       and the expansion is the resultant list.