do echo -e "\n\n\n$i"; cat $i >> ../Newfile.txt; done

for i in ?_*.txt ; do echo -e "\n\n\n$i"; cat $i >> ../Newfile.txt; done

for i in ??_*.txt ; do echo -e "\n\n\n$i"; cat $i >> ../Newfile.txt; done

for i in [0-9]*.txt ; do echo -e "\n\n\n$i"; cat "$i" >> ../Newfile.txt; done

#!/bin/bash

# Pads numbers in file names if found.
# See help message for more.

# Set the environment
shopt -s extglob
IFS=''

BCYAN="${BCYAN:-\e[1;36m}"    #Define text color codes, for prettified output.
RESET="${RESET:-\e[0m}"	      #Overridden by environment defaults if they exist.

#set default padding level
pad=2

# Set up the help dialog
help+=( '' 																					)
help+=( '\tA quick script to zero-pad files that contain numbers.' 										)
help+=( '\tIt will only pad the first number string it finds in the name, and ignores files without numbers.'		)
help+=( '' 																					)
help+=( "\tUsage: \t${BCYAN}${0##*/} [-n <num>] <files>${RESET}"											)
help+=( "\t\t${BCYAN}${0##*/} -h${RESET}" 															)
help+=( '' 																					)
help+=( '\tUse -n to specify the number of digits to pad, from 2-9 digits.  Defaults to '"$pad"' if not used.'	)
help+=( '\tIf no files are given, it processes the current directory.' 									)
help+=( '' 																					)


# Process input options
# "-h" : print help & exit.
# "-n" : test for valid input value and update "pad" variable
while getopts ":hn:" opt; do

     case "$opt" in

          h) IFS=$'\n'
             echo -e "${help[*]}" >&2
             exit "2"
          ;;

          n)	if [[ "$OPTARG" =~ [^[:digit:]] ]] || (( "10#$OPTARG" < 2 )) || (( "10#$OPTARG" > 9 )); then
				echo
				echo -e "${BCYAN}invalid option: [$OPTARG].${RESET}" >&2
				echo -e "${BCYAN}-n must be an integer from 2 to 9${RESET}" >&2
				echo -e "${BCYAN}Falling back to the default of $pad${RESET}"
				echo
			else
				pad="$(( 10#$OPTARG ))"
			fi
          ;;

          \?) echo -e "${BCYAN}Invalid option: [-$OPTARG].  Ignoring.${RESET}" >&2
          ;;
     esac
done

shift $(( OPTIND - 1 )) ; OPTIND=1

# Now check for files in the input.
# If nothing given, set input parameters to files in current directory.
if [[ -z "$*" ]]; then
	set -- ./*
fi

# Process files in input parameters
for file in "$@" ; do

	# Ignore files without digits
	[[ "$file" != *[0-9]* ]] && continue

	# Split filename into prefix-digits-suffix
	[[ "$file" =~ ([^[0-9]*)([0-9]+)(.*) ]]

	# Pad digits to desired width
	printf -v numpad "%0*d" "$pad" "${BASH_REMATCH[2]##*(0)}"

	# Add old and new filenames to arrays for final processing
	oldfile+=( "$file" )
	newfile+=( "${BASH_REMATCH[1]}${numpad}${BASH_REMATCH[3]}" )

done

# If there are any files to rename, ask to confirm the operation.
# And rename if confirmed.
if [[ -n "${oldfile[*]}" ]]; then

	echo
	echo -e "${BCYAN}Rename the following files?${RESET}"
	echo
	for i in "${!oldfile[@]}" ; do
		echo -e "${oldfile[i]/#$PWD/.}\t-->\t${newfile[i]/#$PWD/.}"
	done
	echo

	read -p "(y/n): "
	echo

	case "$REPLY" in

		y|Y*)  	for i in "${!oldfile[@]}" ; do
					mv -n "${oldfile[i]}" "${newfile[i]}"
				done
				echo
				;;

		*)		echo -e "${BCYAN}Aborting.${RESET}"
				echo
				exit 1
				;;
	esac

# Otherwise just exit.
else
	echo
	echo -e "${BCYAN}No files to rename.${RESET}" >&2
	echo -e "${BCYAN}Exiting.${RESET}" >&2
	echo
	exit 1

fi

exit 0

#!/bin/bash

exec 6>&1 >Newfile.txt

for FILE in {1..70}_*
do
    if [[ -e $FILE ]]
    then
        echo -e "$FILE\n"
        cat "$FILE"
        echo
    else
        break
    fi
done

exec >&6 6>&-

for i in ?_*.txt ; do echo -e "\n\n\n$i" >> ../Newfile.txt; cat $i >> ../Newfile.txt; done

1_blah.txt
25_blah.txt
...