Add the 'add-line' and 'remove-line' tools.

README.md

@@ -104,9 +104,25 @@ You must also make sure your filesystem is mounted with ACL support, e.g.:
 
 Don't forget to update /etc/fstab too.
 
+### add-line
+
+Adds a line to the given file if it doesn't already include it.
+
+    /tools/add-line foo.log "hello world"
+    # Same effect:
+    /tools/add-line foo.log hello world
+
+### remove-line
+
+Removes the first instance of a line from the given file. Does nothing if the file doesn't include that line.
+
+    /tools/remove-line foo.log "hello world"
+    # Same effect:
+    /tools/remove-line foo.log hello world
+
 ### truncate
 
-Truncates all passed files to 0 bytes.
+Truncates all given files to 0 bytes.
 
 
 ## RabbitMQ

add-line

@@ -0,0 +1,25 @@
+#!/usr/bin/env ruby
+# encoding: utf-8
+
+def add_line(filename, line)
+	lines = File.open(filename, 'r') do |f|
+		f.binmode
+		f.read.split("\n", -1)
+	end
+	if !lines.include?(line)
+		if lines.last && lines.last.empty?
+			lines.pop
+		end
+		lines << "#{line}\n"
+		File.open(filename, "w") do |f|
+			f.binmode
+			f.write(lines.join("\n"))
+		end
+	end
+end
+
+if ARGV.size < 2
+	abort "Usage: add-line <FILENAME> <LINE>"
+else
+	add_line(ARGV[0], ARGV[1 .. ARGV.size - 1].join(" "))
+end

remove-line

@@ -0,0 +1,22 @@
+#!/usr/bin/env ruby
+# encoding: utf-8
+
+def remove_line(filename, line)
+	lines = File.open(filename, "r") do |f|
+		f.binmode
+		f.read.split("\n", -1)
+	end
+	if index = lines.find_index(line)
+		lines.delete_at(index)
+	end
+	File.open(filename, "w") do |f|
+		f.binmode
+		f.write(lines.join("\n"))
+	end
+end
+
+if ARGV.size < 2
+	abort "Usage: remove-line <FILENAME> <LINE>"
+else
+	remove_line(ARGV[0], ARGV[1 .. ARGV.size - 1].join(" "))
+end