Dear boost list It has been discussed several times already that boost::program_options throws an error if an unknown option is encountered. However, for command line options there is a boolean flag to handle unknown option (presumably?) In program_options/details/cmdline.hpp : cmdline(int argc, const char*const * argv, int style, bool allow_unregistered = false); However, common_command_line_parser::run(), when constructing a cmdline object does not forward this flag. I suggest that you change the signature of the run() method to forward that flag, and modify the code section in program_options/src/parsers.cpp current version: parsed_options common_command_line_parser::run() const { parsed_options result(m_desc); detail::cmdline cmd(m_args, m_style); cmd.set_additional_parser(m_ext); if (m_desc) { set<string> keys = m_desc->primary_keys(); for (set<string>::iterator i = keys.begin(); i != keys.end (); ++i) { const option_description& d = m_desc->find(*i); char s = d.short_name().empty() ? '\0' : d.short_name ()[0]; ........... new suggestion: parsed_options common_command_line_parser::run(bool allow_unregistered) const { parsed_options result(m_desc); detail::cmdline cmd(m_args, m_style, allow_unregistered); cmd.set_additional_parser(m_ext); if (m_desc) { set<string> keys = m_desc->primary_keys(); for (set<string>::iterator i = keys.begin(); i != keys.end (); ++i) { const option_description& d = m_desc->find(*i); char s = d.short_name().empty() ? '\0' : d.short_name ()[0]; ........... Does this allow then parsing cmd line option strings which contain unknown options without throwing exceptions? Comment very welcome. Freundliche Grüsse Daniel Egloff Zürcher Kantonalbank, VFEF Josefstrasse 222, 8005 Zürich Tel. +41 (0) 44 292 45 33, Fax +41 (0) 44 292 45 93 Briefadresse: Postfach, 8010 Zürich, http://www.zkb.ch ___________________________________________________________________ Disclaimer: Diese Mitteilung ist nur fuer die Empfaengerin / den Empfaenger bestimmt. Fuer den Fall, dass sie von nichtberechtigten Personen empfangen wird, bitten wir diese hoeflich, die Mitteilung an die ZKB zurueckzusenden und anschliessend die Mitteilung mit allen Anhaengen sowie allfaellige Kopien zu vernichten bzw. zu loeschen. Der Gebrauch der Information ist verboten. This message is intended only for the named recipient and may contain confidential or privileged information. If you have received it in error, please advise the sender by return e-mail and delete this message and any attachments. Any unauthorised use or dissemination of this information is strictly prohibited.