Add a simple readline recipe.

setup.py

@@ -165,6 +165,7 @@ setup(name=name,
           'publish.serialised = slapos.recipe.publish:Serialised',
           'publishsection = slapos.recipe.publish:PublishSection',
           'publishurl = slapos.recipe.publishurl:Recipe',
+          'readline = slapos.recipe.readline:Recipe',
           'redis.server = slapos.recipe.redis:Recipe',
           'request = slapos.recipe.request:Recipe',
           'request.serialised = slapos.recipe.request:Serialised',

slapos/recipe/readline.py

+# vim: set et sts=2:
+##############################################################################
+#
+# Copyright (c) 2013 Vifib SARL and Contributors. All Rights Reserved.
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsibility of assessing all potential
+# consequences resulting from its eventual inadequacies and bugs
+# End users who are looking for a ready-to-use solution with commercial
+# guarantees and support are strongly adviced to contract a Free Software
+# Service Company
+#
+# This program is Free Software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 3
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+#
+##############################################################################
+
+import errno
+
+class Recipe(object):
+  """Read the first line of a file.
+
+  As the result has to be provided as an options, it is mandatory that the
+  buildout profile fills the file content (if needed) before trying to read it.
+
+    Options:
+    - storage-path: file to read
+
+    Result set in options:
+    - readline: first line of the file
+  """
+
+  def __init__(self, buildout, name, options):
+    storage_path = options['storage-path']
+    try:
+      with open(storage_path) as f:
+        readline = f.readline()
+    except IOError, e:
+      if e.errno != errno.ENOENT:
+        raise
+      readline = None
+
+    self.readline = readline
+    options['readline'] = readline
+
+  def install(self):
+    if self.readline is None:
+      raise ValueError('Unable to read the file content.')
+    return ()
+
+  def update(self):
+    return ()