Here is a simple Python script to trigger an ir.cron job from the command-line system.

I created this to let my customer use his proprietary job scheduler to trigger OpenERP tasks. It was tested on OpenERP 6.1. 

 1#!/usr/bin/python
 2
 3import sys
 4import traceback
 5import xmlrpclib
 6from optparse import OptionParser
 7from datetime.datetime import now
 8
 9parser = OptionParser()
10parser.add_option("-d", "--db", dest="db_name", help="OpenERP database name", metavar="DB_NAME", default="openerp")
11parser.add_option("-p", "--password", dest="password", help="OpenERP admin password", metavar="ADMIN_PASSWORD", default="admin")
12parser.add_option("-n", "--name", dest="cron_name", help="OpenERP ir.cron object name", metavar="CRON_NAME")
13
14(options, args) = parser.parse_args()
15
16assert options.cron_name
17
18# Query helpers
19sock = xmlrpclib.ServerProxy('http://localhost:8069/xmlrpc/object')
20q = lambda * a: sock.execute(options.db_name, 1, options.password, *a)
21
22try:
23    ir_cron_ids = q('ir.cron', 'search', [('name', '=', options.cron_name)])
24    if not ir_cron_ids:
25        raise "No cron found in OpenERP."
26    for ir_cron in q('ir.cron', 'read', ir_cron_ids, ['model', 'function', 'args']):
27        print "%s, %s - (%s) %s %s%s" % (options.db_name, now().strftime('%Y-%m-%d %H:%M:%S'), ir_cron['id'], ir_cron['model'], ir_cron['function'], ir_cron['args'])
28        q(ir_cron['model'], ir_cron['function'], *eval('tuple(%s)' % (ir_cron['args'] or '')))
29except:
30    traceback.print_exc(file=sys.stdout)
31    sys.exit(8)
32
33sys.exit()