Script for aligning a Markdown table neatly. Put in your PATH as mdtable then use in Vim visual mode: !mdtable

mdtable.rb

#!/usr/bin/env ruby

table = ARGF.read.chomp

parse_row = ->(row) { row.gsub(/^\||\|$/, "").split("|").map(&:strip) }
rows = table.each_line.map(&parse_row)

# Normalise column count
column_count = rows.map(&:length).max
rows = rows.map { |row| (row + ([""] * column_count)).take(column_count) }

# Find longest value for each column
columns = 1.upto(column_count).map { |n| rows.map { |row| row[n - 1] } }
column_widths = columns.map { |cells| cells.map(&:length).max }

# Expand each cell to the right size for its column
rows = rows.map do |row|
  row.zip(column_widths).map do |value, length|
    # If it's a header row, expand the dashes all the way across the cell
    if value =~ /^[\s\-]{2,}$/
      "-" * (length + 2)
    # Otherwise, pad the string to the correct length with spaces around
    else
      " #{value.ljust(length)} "
    end
  end
end

# Display the table
rows.each do |row|
  puts "|#{row.join("|")}|"
end