Sequentially Named File Generator. A bash shell script that creates a next 4-digit numbered file.

touch_NNNN.sh

#!/bin/bash
# -------------------------------------------------------
# Sequentially Named File Generator. 
#
# Create a new numbered file based on the given filename.
#
# Example:
#
# * "test.txt" -> "test####.txt"
# * "test" -> "test####"
# * ".txt" -> "####.txt"
# * "" -> "####"
# -------------------------------------------------------

shopt -s nullglob

num_pat="[0-9][0-9][0-9][0-9]"
file_prefix="${1%.*}"
[[ $1 = *.* ]] && file_ext="${1##*.}"
[ -n "$file_ext" ] && file_ext=.$file_ext

echo "[$0] prefix=\"$file_prefix\" suffix=\"$file_ext\""

echo "[$0] Checking \"${file_prefix}NNNN${file_ext}\" ..."
current_list=($file_prefix$num_pat$file_ext)
echo $current_list
if [ -z "$current_list" ]
then
  echo "[$0] No matching file found."
  num=0
else
  last_file=${current_list[${#current_list[@]}-1]}
  echo "[$0] \"$last_file\" found."
  num="${last_file##$file_prefix}"
  num="${num%*$file_ext}"
  num=$((++num))
  echo $num
fi

new_file_name=$(printf "%s%04d%s" "$file_prefix" "$num" "$file_ext")

echo "[$0] Creating \"$new_file_name\" ..."

touch "$new_file_name"