#!/bin/bash
## Change file names into uppper/lower case, or by position.
NO_ARGS=0 
E_OPTERROR=65
DEBUG=0
UPPER=0
FNAME="f"
maxdepth=1
directory=`pwd`
set -o noglob
#---- Functions ------------#

usage() {
 printf "Usage: `basename $0` [-D directory] [-M depth] [-U ] [-p pattern] [-c position ][-d] [-X] [filename(s)]\n"
 cat << EOF
        -D : starting directory. Default=current directory
        -M : max depth to recurse subdirectories (default=1), eg 1,2
        -U : Change all letters to upper case. Default: change to all lower case
        -c position : Change character at position to upper or lower (-U or -L)
        -p pattern: Change the word matched by pattern to upper/lower case
        -d : Debugging mode. Used to list all files to be changed, without changes taking effect
        -X : Only check directory names, not file names
        filename(s) : file names eg "*.txt". If omitted, default to all files. Use quotes.
        Example: 
        1) -U -p file "*.txt" ===> change all name of text files with pattern "file" to upper case.
        2) -U -c 10 "*.txt" ===> change the 10th character to upper case
        3) -c 2 "*FILE*" ===> change the 2nd character to lower case for all files with pattern "FILE" in file name.
EOF

}
#----------------------------#

if [ $# -eq "$NO_ARGS" ]  # Script invoked with no command-line args?
then
   usage
   exit $E_OPTERROR        # Exit and explain usage, if no argument(s) given.
fi  


while getopts ":D:s:e:M:p:c:dUX" Option
do
  case $Option in
    D     ) directory=$OPTARG
            ;;
    d     ) DEBUG=1 ;;
    U     ) UPPER=1;;
    c     ) position=$OPTARG
            case ${position} in
               0 | *[a-z]*) position=1;;      
            esac
            ;;
    p     ) pattern=$OPTARG
            [ -z "${pattern}" ] && pattern=".*"
            ;;
    M     ) maxdepth=$OPTARG
            case ${maxdepth} in
                0 | *[a-z]*|"") maxdepth=1;;   
            esac
            ;;
    X     ) FNAME="d";;
    *     ) echo "Unimplemented option chosen."
            exit;;
  esac
done
shift $(($OPTIND - 1))

# get last argument

argument=$#
if [ $argument -eq 0 ];then
    ext="*"
else    
    ext=$(eval echo \"\${${argument}}\")
fi


find "${directory}" -maxdepth "${maxdepth}" -type "${FNAME}" -name "$ext" -printf "%f:%h:%p\n" | \
awk -F":" -v pattern="${pattern}" -v debug="$DEBUG" -v upper=${UPPER} -v position="${position}" 'BEGIN{
    q="\042"
}
$1 ~ pattern{  
    if ( upper ) {
        
        if ( position>0 ) {
            #change only positional characters to upper
            newname = substr($1,1,position-1) toupper(substr($1,position,1)) substr($1,position+1)        
        }else if ( int(position)<0 ) {
            #change to upper from the back
            newname = substr($1,1,length($1)+position) toupper(substr($1,length($1)+position+1))            
        }else if ( !position  )  {
            # change all characters to upper            
            if (  pattern == ".*" ) {
                newname = toupper($1)
            }else {
                newname=$1
                gsub(pattern,toupper(pattern),newname)            
            }
        }
    }else if (!upper) { 
        if ( position>0 )  {
            # change only positional characters to lower
            newname = substr($1,1,position-1) tolower(substr($1,position,1)) substr($1,position+1)                
        }else if ( int(position)<0  ){
            #change to lower from the back
            newname = substr($1,1,length($1)+position) tolower(substr($1,length($1)+position+1))
        }else if (!position) {
            # change all characters to lower
            if (  pattern == ".*" ) {
                newname = tolower($1)
            }else {
                newname=$1
                gsub(pattern,tolower(pattern),newname)            
            }                
        }
    }
    if ( newname == $1 ) {next}    
    if ( debug) {
        print "mv -u " q $3 q " "q $2 "/" newname q        
    }else {
        cmd = "mv -u " q $3 q " "q $2 "/" newname q        
        system(cmd)
    }
    
}'