Shell Programming and Scripting

#!/bin/sh

Usage() {
   [ $# -ne 0 ] && echo "\n$*\n" >&2
   cat <<-EOD_USAGE >&2
        Usage: $0 file... target
        file...  List of files to rename
        target   Target name

        EOD_USAGE
   exit 1
}

#
# Get and verify arguments
#

# Argument count

[ $# -lt 2 ] && Usage "Missing arguments." 

# Files to rename

while [ $# -gt 1 ]
do
   file=$1
   case "$file" in
      *.*.*|*\**) Usage "Invalid file name : $file" ;;
   esac
   [ -e "$file" ] || Usage "File not found : $file"
   file_list="$file_list $file"
   shift
done

# Target name

target=$1
case "$target" in
   *.*.*|*\**\**) Usage "Invalid target name : $file" ;;
esac
target_nam=`echo "$target" | cut -d. -f1`
target_ext=`echo "$target" | cut -d. -f2` 

#
# Rename loop
#

for file in $file_list
do
   # Actual file name and extension

   file_nam=`echo "$file" | cut -d. -f1`
   file_ext=`echo "$file" | cut -d. -f2` 
 
   # New file name and extension

   if [ "$target_nam" = '*' ]
      then new_nam="$file_nam"
      else new_nam="$target_nam"
   fi
   if [ "$target_ext" = '*' ]
      then new_ext="$file_ext"
      else new_ext="$target_ext"
   fi
   [ -n "$file_ext" ] && file_ext=".$file_ext"
   [ -n "$new_ext" ] && new_ext=".$new_ext"
   new="${new_nam}${new_ext}"

   # Rename

   echo "Rename file $file to $new ..."
   if [ -e "$new" ]
      then echo "Not renamed, target file already exists : $new" >&2
      else mv "$file" "$new"
   fi
done