chore(user/zeropad.sh):Add some comments

[BK-2020-03.git] / user / zeropad.sh

#!/bin/bash
# Desc: Zero-pad working dir files with initial digits for sorting
# Usage: zeropad.sh
# Version: 0.0.4

list_files() {
    # Desc: Lists working directory file basenames
    # Usage: list_files
    # Input: none
    # Output: stdout  a line-delimited list of file names
    find . -mindepth 1 -maxdepth 1 -type f -exec basename '{}' \; ;
}; # list pwd file basenames
main () {
    # Find the maximum number of leading digits in the filenames of working dir
    max_digits="$(list_files | sed -e 's/[^0-9].*//' | awk '{ if(length > L) L=length } END { print L }')";
    # declare -p max_digits; # debug

    # Loop over the files and rename them
    while read -r file; do
        re='^[0-9]+';
        if [[ ! "$file" =~ $re ]]; then continue; fi;

        # Extract the leading digits
        digits="$(echo "$file" | sed 's/\([0-9]*\).*/\1/')";
        # Zero-pad the digits
        padded_digits="$(printf "%0${max_digits}d" "$digits")";
        # Construct the new filename
        new_file="${padded_digits}${file#${digits}}";
        # Rename the file
        mv -n "$file" "$new_file"
        # declare -p file new_file; # debug
    done < <(list_files);
}; # main program

main "$@";

# Author: Steven Baltakatei Sandoval
# License: GPLv3+