Simple script to handle multi-line logs

log_pipe.rb

#!/usr/bin/env ruby

# # Simple script to handle multi-line logs.
# Adjust the global vars as needed.
#
# # Usage
#
#     > chmod +x log_pipe.rb
#     > tail -f log/development.log | ./log_pipe.rb 
#
# TODO read some options from command line.

# Pattern used to detect the beginning of a log group.
$group_pattern = /^\d{4}.*\|/

# Ignore lines that match this pattern.
# This one will filter out DEBUG logs with timing metics,
# which happens to filter out SQL logs.
# A little more surgical would be to look for SQL keywords.
$skip_pattern = /DEBUG\|[^\(]+\(\d+\.?\d*?ms\)/

# Hate ANSI colors? This pattern kills them.
# Set to `false` if you don't hate colors.
$ansi_escape_pattern = /\e\[[^m]+m/

$redirect = $stdout

def grouped(lines)
  first = lines.first
  return if first.nil? || first =~ $skip_pattern

  # strip ANSI escapes
  if $ansi_escape_pattern
    lines = lines.map { |l| l.gsub($ansi_escape_pattern, '') }
  end
  $redirect.puts lines
end

line_group = []
ARGF.each_line do |line|
  if line =~ $group_pattern
    grouped(line_group)
    line_group = [line]
  else
    line_group << line
  end
end
grouped(line_group)