Formatting assembly comments using Bash

assembly_formatter.sh

#!/bin/bash
#
# Programmer: Jacob Young
# Filename: comments.sh
# Date: Mon Dec 7 2015
# Class: COSMC-171
#
# Assignment 1
# This script will align comments in an assmebly language file
# Lines which start with a comment (;) will not be modified
# Comments which come after a line of code, should be aligned
#   4 columns after the longest line of code.

# Array to hold all lines of input
Line=()
# The longest number of "code characters"
declare -i Longest=0

# Reading input from stdin
while IFS='' read line; do
  Lines+=("$line")
done

# Check all lines, find the line with the most "code characters"
for line in "${Lines[@]}"; do
  # If the line begins with a comment, skip it
  if [[ ${line:0:1} == ";" ]]; then
    continue
  else
    temp="${line%;*}"                                         # Taking out the inline comment
    temp="$(echo -e "${temp}" | sed -e 's/[[:space:]]*$//')"  # Using sed to remove trailing whitespace
    #echo "$temp"
    # If the number of code characters is longer than the previous max, set the new max
    if [[ "${#temp}" -gt "$Longest" ]]; then
      Longest="${#temp}"
    fi
  fi
done

# At this point, we need to shift all lines with comments to be at position 27+4
FinalColumn=$(( $Longest + 5 ))

for line in "${Lines[@]}"; do
  # Skipping lines with comment at the start
  if [[ ${line:0:1} == ";" ]]; then
    echo "$line"
  else
    semicolon=$(( $(expr index "$line" ';') - 1 ))
    offset=$(( $FinalColumn - $semicolon - 1 ))    # Calculate the offset for the current line
    whitespace=$(printf "%-"$offset"s" "") 		      # Create some whitespace to fill in
    whitespace="${whitespace// / }" 			      # Do some bash magic
    old_comment="${line:$semicolon}"
    new_comment="$whitespace""${line:$semicolon}"
    echo "${line/$old_comment/$new_comment}"
  fi
done