merge-zsh-history

#!/usr/bin/env ruby

# Merge zsh's history files and print them to stdout.
# Entries are sorted by timestamp.
#
# usage:
#   merge-zsh-history file1 file2 ...

# format of history entry
#
# single line
# : 1400003117:0;cp foo bar
#
# multi lines
# : 1400041717:0;ruby -ve 'def f(x); end\
# f(a: 1,\
# b: 2,\
# )'

entries = []
ARGV.each do |arg|
  File.open(arg, 'rb') do |f|
    while line = f.gets
      lines = [line]
      while lines.last.end_with?("\\\n")
        lines << f.gets
      end

      time = lines[0].scan(/\A: ([0-9]+):/).flatten[0]
      if time.nil?
        raise "format error: #{lines.join}"
      end
      time = time.to_i
      entries << [time, lines]
    end
  end
  entries.sort_by!(&:first)
end

entries.each do |_, lines|
  print lines.join
end