Make libnetcfg by default display the libnet configuration,

-c to change, add -i for old config, document all options,
regen toc.

p4raw-id: //depot/perl@10701

3 files changed, 228 insertions, 83 deletions

diff --git a/pod/perltoc.pod b/pod/perltoc.pod
index c355166748..1094d8c92d 100644
--- a/pod/perltoc.pod
+++ b/pod/perltoc.pod
@@ -839,10 +839,10 @@ cmd, H -number, q or ^D, R, |dbcmd, ||dbcmd, command, m expr, man [manpage]
 
 C<recallCommand>, C<ShellBang>, C<pager>, C<tkRunning>, C<signalLevel>,
 C<warnLevel>, C<dieLevel>, C<AutoTrace>, C<LineInfo>, C<inhibit_exit>,
-C<PrintRet>, C<ornaments>, C<frame>, C<maxTraceLen>, C<arrayDepth>,
-C<hashDepth>, C<compactDump>, C<veryCompact>, C<globPrint>, C<DumpDBFiles>,
-C<DumpPackages>, C<DumpReused>, C<quote>, C<HighBit>, C<undefPrint>,
-C<UsageOnly>, C<TTY>, C<noTTY>, C<ReadLine>, C<NonStop>
+C<PrintRet>, C<ornaments>, C<frame>, C<maxTraceLen>, C<windowSize>,
+C<arrayDepth>, C<hashDepth>, C<compactDump>, C<veryCompact>, C<globPrint>,
+C<DumpDBFiles>, C<DumpPackages>, C<DumpReused>, C<quote>, C<HighBit>,
+C<undefPrint>, C<UsageOnly>, C<TTY>, C<noTTY>, C<ReadLine>, C<NonStop>
 
 =item Debugger input/output
 
@@ -2170,6 +2170,8 @@ chcp, dataset access, OS/390, z/OS iconv, locales
 
 =item Perl Modules
 
+=item Making your module threadsafe
+
 =back
 
 =item SEE ALSO
@@ -2205,30 +2207,34 @@ Class::Struct, Cwd, DB, DB_File, Devel::SelfStubber, Digest, DirHandle,
 Dumpvalue, Encode, Encode::EncodeFormat, Encode::Tcl, English, Env,
 Exporter, Exporter::Heavy, ExtUtils::Command, ExtUtils::Constant,
 ExtUtils::Embed, ExtUtils::Install, ExtUtils::Installed, ExtUtils::Liblist,
-ExtUtils::MM_Cygwin, ExtUtils::MM_OS2, ExtUtils::MM_Unix, ExtUtils::MM_VMS,
-ExtUtils::MM_Win32, ExtUtils::MakeMaker, ExtUtils::Manifest,
-ExtUtils::Mkbootstrap, ExtUtils::Mksymlists, ExtUtils::Packlist,
-ExtUtils::testlib, Fatal, Fcntl, File::Basename, File::CheckTree,
-File::Compare, File::Copy, File::DosGlob, File::Find, File::Path,
-File::Spec, File::Spec::Epoc, File::Spec::Functions, File::Spec::Mac,
-File::Spec::OS2, File::Spec::Unix, File::Spec::VMS, File::Spec::Win32,
-File::Temp, File::stat, FileCache, FileHandle, Filter::Simple, FindBin,
-Getopt::Long, Getopt::Std, I18N::Collate, I18N::LangTags,
-I18N::LangTags::List, IO, IPC::Open2, IPC::Open3, Locale::Constants,
-Locale::Country, Locale::Currency, Locale::Language, Locale::Maketext,
-Locale::Maketext::TPJ13, Math::BigFloat, Math::BigInt, Math::Complex,
-Math::Trig, NDBM_File, NEXT, Net::Ping, Net::hostent, Net::netent,
-Net::protoent, Net::servent, O, ODBM_File, Opcode, POSIX, PerlIO,
-Pod::Checker, Pod::Find, Pod::Html, Pod::InputObjects, Pod::LaTeX,
-Pod::Man, Pod::ParseUtils, Pod::Parser, Pod::Plainer, Pod::Select,
-Pod::Text, Pod::Text::Color, Pod::Text::Overstrike, Pod::Text::Termcap,
-Pod::Usage, SDBM_File, Safe, Search::Dict, SelectSaver, SelfLoader, Shell,
-Socket, Storable, Switch, Symbol, Term::ANSIColor, Term::Cap,
-Term::Complete, Term::ReadLine, Test, Test::Harness, Text::Abbrev,
-Text::Balanced, Text::ParseWords, Text::Soundex, Text::Tabs, Text::Wrap,
-Tie::Array, Tie::Handle, Tie::Hash, Tie::RefHash, Tie::Scalar,
-Tie::SubstrHash, Time::Local, Time::gmtime, Time::localtime, Time::tm,
-UNIVERSAL, User::grent, User::pwent, Win32
+ExtUtils::MM_Cygwin, ExtUtils::MM_NW5, ExtUtils::MM_OS2, ExtUtils::MM_Unix,
+ExtUtils::MM_VMS, ExtUtils::MM_Win32, ExtUtils::MakeMaker,
+ExtUtils::Manifest, ExtUtils::Mkbootstrap, ExtUtils::Mksymlists,
+ExtUtils::Packlist, ExtUtils::testlib, Fatal, Fcntl, File::Basename,
+File::CheckTree, File::Compare, File::Copy, File::DosGlob, File::Find,
+File::Path, File::Spec, File::Spec::Epoc, File::Spec::Functions,
+File::Spec::Mac, File::Spec::OS2, File::Spec::Unix, File::Spec::VMS,
+File::Spec::Win32, File::Temp, File::stat, FileCache, FileHandle,
+Filter::Simple, FindBin, Getopt::Long, Getopt::Std, I18N::Collate,
+I18N::LangTags, I18N::LangTags::List, IO, IPC::Open2, IPC::Open3,
+Locale::Constants, Locale::Country, Locale::Currency, Locale::Language,
+Locale::Maketext, Locale::Maketext::TPJ13, Math::BigFloat, Math::BigInt,
+Math::Complex, Math::Trig, Memoize, Memoize::AnyDBM_File, Memoize::Expire,
+Memoize::ExpireFile, Memoize::ExpireTest, Memoize::NDBM_File,
+Memoize::SDBM_File, Memoize::Saves, Memoize::Storable, NDBM_File, NEXT,
+Net::Cmd, Net::Config, Net::Domain, Net::DummyInetd, Net::FTP, Net::NNTP,
+Net::Netrc, Net::PH, Net::POP3, Net::Ping, Net::SMTP, Net::SNPP, Net::Time,
+Net::hostent, Net::libnetFAQ, Net::netent, Net::protoent, Net::servent, O,
+ODBM_File, Opcode, POSIX, PerlIO, Pod::Checker, Pod::Find, Pod::Html,
+Pod::InputObjects, Pod::LaTeX, Pod::Man, Pod::ParseUtils, Pod::Parser,
+Pod::Plainer, Pod::Select, Pod::Text, Pod::Text::Color,
+Pod::Text::Overstrike, Pod::Text::Termcap, Pod::Usage, SDBM_File, Safe,
+Search::Dict, SelectSaver, SelfLoader, Shell, Socket, Storable, Switch,
+Symbol, Term::ANSIColor, Term::Cap, Term::Complete, Term::ReadLine, Test,
+Test::Harness, Text::Abbrev, Text::Balanced, Text::ParseWords,
+Text::Soundex, Text::Tabs, Text::Wrap, Tie::Array, Tie::Handle, Tie::Hash,
+Tie::RefHash, Tie::Scalar, Tie::SubstrHash, Time::Local, Time::gmtime,
+Time::localtime, Time::tm, UNIVERSAL, User::grent, User::pwent, Win32
 
 =item Extension Modules
 
@@ -3787,15 +3793,19 @@ callback
 
 =item DOCUMENTATION
 
-L<libnetcfg|libnetcfg>, L<perldoc|perldoc>, L<pod2man|pod2man> and
-L<pod2text|pod2text>, L<pod2html|pod2html> and L<pod2latex|pod2latex>,
-L<pod2usage|pod2usage>, L<podselect|podselect>, L<podchecker|podchecker>,
-L<splain|splain>, L<roffitall|roffitall>
+L<perldoc|perldoc>, L<pod2man|pod2man> and L<pod2text|pod2text>,
+L<pod2html|pod2html> and L<pod2latex|pod2latex>, L<pod2usage|pod2usage>,
+L<podselect|podselect>, L<podchecker|podchecker>, L<splain|splain>,
+L<roffitall|roffitall>
 
 =item CONVERTORS
 
 L<a2p|a2p>, L<s2p|s2p>, L<find2perl|find2perl>
 
+=item Administration
+
+L<libnetcfg|libnetcfg>
+
 =item Development
 
 L<perlbug|perlbug>, L<h2ph|h2ph>, L<c2ph|c2ph> and L<pstruct|pstruct>,
@@ -3888,44 +3898,53 @@ hv_iterval, hv_magic, hv_store, hv_store_ent, hv_undef, isALNUM, isALPHA,
 isDIGIT, isLOWER, isSPACE, isUPPER, is_utf8_char, is_utf8_string, items,
 ix, LEAVE, load_module, looks_like_number, MARK, mg_clear, mg_copy,
 mg_find, mg_free, mg_get, mg_length, mg_magical, mg_set, Move, New, newAV,
-Newc, newCONSTSUB, newHV, newRV_inc, newRV_noinc, NEWSV, newSViv, newSVnv,
-newSVpv, newSVpvf, newSVpvn, newSVpvn_share, newSVrv, newSVsv, newSVuv,
-newXS, newXSproto, Newz, Nullav, Nullch, Nullcv, Nullhv, Nullsv, ORIGMARK,
-perl_alloc, perl_construct, perl_destruct, perl_free, perl_parse, perl_run,
-PL_modglobal, PL_na, PL_sv_no, PL_sv_undef, PL_sv_yes, POPi, POPl, POPn,
-POPp, POPpbytex, POPpx, POPs, PUSHi, PUSHMARK, PUSHn, PUSHp, PUSHs, PUSHu,
-PUTBACK, Renew, Renewc, require_pv, RETVAL, Safefree, savepv, savepvn,
-SAVETMPS, SP, SPAGAIN, ST, strEQ, strGE, strGT, strLE, strLT, strNE,
-strnEQ, strnNE, StructCopy, SvCUR, SvCUR_set, SvEND, SvGETMAGIC, SvGROW,
-SvIOK, SvIOKp, SvIOK_notUV, SvIOK_off, SvIOK_on, SvIOK_only, SvIOK_only_UV,
-SvIOK_UV, SvIV, SvIVX, SvLEN, SvNIOK, SvNIOKp, SvNIOK_off, SvNOK, SvNOKp,
-SvNOK_off, SvNOK_on, SvNOK_only, SvNV, SvNVX, SvOK, SvOOK, SvPOK, SvPOKp,
-SvPOK_off, SvPOK_on, SvPOK_only, SvPOK_only_UTF8, SvPV, SvPVX, SvPV_force,
+Newc, newCONSTSUB, newHV, newRV_inc, newRV_noinc, newSV, NEWSV, newSViv,
+newSVnv, newSVpv, newSVpvf, newSVpvn, newSVpvn_share, newSVrv, newSVsv,
+newSVuv, newXS, newXSproto, Newz, Nullav, Nullch, Nullcv, Nullhv, Nullsv,
+ORIGMARK, perl_alloc, perl_clone, perl_construct, perl_destruct, perl_free,
+perl_parse, perl_run, PL_modglobal, PL_na, PL_sv_no, PL_sv_undef,
+PL_sv_yes, POPi, POPl, POPn, POPp, POPpbytex, POPpx, POPs, PUSHi, PUSHMARK,
+PUSHn, PUSHp, PUSHs, PUSHu, PUTBACK, Renew, Renewc, require_pv, RETVAL,
+Safefree, savepv, savepvn, SAVETMPS, SP, SPAGAIN, ST, strEQ, strGE, strGT,
+strLE, strLT, strNE, strnEQ, strnNE, StructCopy, SvCUR, SvCUR_set, SvEND,
+SvGETMAGIC, SvGROW, SvIOK, SvIOKp, SvIOK_notUV, SvIOK_off, SvIOK_on,
+SvIOK_only, SvIOK_only_UV, SvIOK_UV, SvIV, SvIVx, SvIVX, SvLEN, SvNIOK,
+SvNIOKp, SvNIOK_off, SvNOK, SvNOKp, SvNOK_off, SvNOK_on, SvNOK_only, SvNV,
+SvNVx, SvNVX, SvOK, SvOOK, SvPOK, SvPOKp, SvPOK_off, SvPOK_on, SvPOK_only,
+SvPOK_only_UTF8, SvPV, SvPVbyte, SvPVbytex, SvPVbytex_force,
+SvPVbyte_force, SvPVbyte_nolen, SvPVutf8, SvPVutf8x, SvPVutf8x_force,
+SvPVutf8_force, SvPVutf8_nolen, SvPVx, SvPVX, SvPV_force, SvPV_force_nomg,
 SvPV_nolen, SvREFCNT, SvREFCNT_dec, SvREFCNT_inc, SvROK, SvROK_off,
-SvROK_on, SvRV, SvSETMAGIC, SvSetSV, SvSetSV_nosteal, SvSTASH, SvTAINT,
-SvTAINTED, SvTAINTED_off, SvTAINTED_on, SvTRUE, svtype, SvTYPE, SVt_IV,
-SVt_NV, SVt_PV, SVt_PVAV, SVt_PVCV, SVt_PVHV, SVt_PVMG, SvUOK, SvUPGRADE,
-SvUTF8, SvUTF8_off, SvUTF8_on, SvUV, SvUVX, sv_2mortal, sv_bless, sv_catpv,
-sv_catpvf, sv_catpvf_mg, sv_catpvn, sv_catpvn_flags, sv_catpvn_mg,
-sv_catpv_mg, sv_catsv, sv_catsv_flags, sv_catsv_mg, sv_chop, sv_clear,
-sv_cmp, sv_cmp_locale, sv_dec, sv_derived_from, sv_eq, sv_free, sv_getcwd,
-sv_gets, sv_grow, sv_inc, sv_insert, sv_isa, sv_isobject, sv_len,
-sv_len_utf8, sv_magic, sv_mortalcopy, sv_newmortal, sv_pvn_force,
-sv_pvn_force_flags, sv_pvutf8n_force, sv_realpath, sv_reftype, sv_replace,
-sv_rvweaken, sv_setiv, sv_setiv_mg, sv_setnv, sv_setnv_mg, sv_setpv,
-sv_setpvf, sv_setpvf_mg, sv_setpviv, sv_setpviv_mg, sv_setpvn,
+SvROK_on, SvRV, SvSETMAGIC, SvSetMagicSV, SvSetMagicSV_nosteal, SvSetSV,
+SvSetSV_nosteal, SvSTASH, SvTAINT, SvTAINTED, SvTAINTED_off, SvTAINTED_on,
+SvTRUE, svtype, SvTYPE, SVt_IV, SVt_NV, SVt_PV, SVt_PVAV, SVt_PVCV,
+SVt_PVHV, SVt_PVMG, SvUOK, SvUPGRADE, SvUTF8, SvUTF8_off, SvUTF8_on, SvUV,
+SvUVx, SvUVX, sv_2bool, sv_2cv, sv_2io, sv_2iv, sv_2mortal, sv_2nv,
+sv_2pvbyte, sv_2pvbyte_nolen, sv_2pvutf8, sv_2pvutf8_nolen, sv_2pv_flags,
+sv_2pv_nolen, sv_2uv, sv_backoff, sv_bless, sv_catpv, sv_catpvf,
+sv_catpvf_mg, sv_catpvn, sv_catpvn_flags, sv_catpvn_mg, sv_catpv_mg,
+sv_catsv, sv_catsv_flags, sv_catsv_mg, sv_chop, sv_clear, sv_cmp,
+sv_cmp_locale, sv_collxfrm, sv_dec, sv_derived_from, sv_eq,
+sv_force_normal, sv_force_normal_flags, sv_free, sv_getcwd, sv_gets,
+sv_grow, sv_inc, sv_insert, sv_isa, sv_isobject, sv_iv, sv_len,
+sv_len_utf8, sv_magic, sv_mortalcopy, sv_newmortal, sv_newref, sv_nv,
+sv_pos_b2u, sv_pos_u2b, sv_pv, sv_pvbyte, sv_pvbyten, sv_pvbyten_force,
+sv_pvn, sv_pvn_force, sv_pvn_force_flags, sv_pvutf8, sv_pvutf8n,
+sv_pvutf8n_force, sv_realpath, sv_reftype, sv_replace, sv_report_used,
+sv_reset, sv_rvweaken, sv_setiv, sv_setiv_mg, sv_setnv, sv_setnv_mg,
+sv_setpv, sv_setpvf, sv_setpvf_mg, sv_setpviv, sv_setpviv_mg, sv_setpvn,
 sv_setpvn_mg, sv_setpv_mg, sv_setref_iv, sv_setref_nv, sv_setref_pv,
 sv_setref_pvn, sv_setref_uv, sv_setsv, sv_setsv_flags, sv_setsv_mg,
-sv_setuv, sv_setuv_mg, sv_true, sv_unmagic, sv_unref, sv_unref_flags,
-sv_upgrade, sv_usepvn, sv_usepvn_mg, sv_utf8_decode, sv_utf8_downgrade,
-sv_utf8_encode, sv_utf8_upgrade, sv_utf8_upgrade_flags, sv_vcatpvfn,
-sv_vsetpvfn, THIS, toLOWER, toUPPER, utf8n_to_uvchr, utf8n_to_uvuni,
-utf8_distance, utf8_hop, utf8_length, utf8_to_bytes, utf8_to_uvchr,
-utf8_to_uvuni, uvchr_to_utf8, uvuni_to_utf8, warn, XPUSHi, XPUSHn, XPUSHp,
-XPUSHs, XPUSHu, XS, XSRETURN, XSRETURN_EMPTY, XSRETURN_IV, XSRETURN_NO,
-XSRETURN_NV, XSRETURN_PV, XSRETURN_UNDEF, XSRETURN_YES, XST_mIV, XST_mNO,
-XST_mNV, XST_mPV, XST_mUNDEF, XST_mYES, XS_VERSION, XS_VERSION_BOOTCHECK,
-Zero
+sv_setuv, sv_setuv_mg, sv_taint, sv_tainted, sv_true, sv_unmagic, sv_unref,
+sv_unref_flags, sv_untaint, sv_upgrade, sv_usepvn, sv_usepvn_mg,
+sv_utf8_decode, sv_utf8_downgrade, sv_utf8_encode, sv_utf8_upgrade,
+sv_utf8_upgrade_flags, sv_uv, sv_vcatpvfn, sv_vsetpvfn, THIS, toLOWER,
+toUPPER, utf8n_to_uvchr, utf8n_to_uvuni, utf8_distance, utf8_hop,
+utf8_length, utf8_to_bytes, utf8_to_uvchr, utf8_to_uvuni, uvchr_to_utf8,
+uvuni_to_utf8, warn, XPUSHi, XPUSHn, XPUSHp, XPUSHs, XPUSHu, XS, XSRETURN,
+XSRETURN_EMPTY, XSRETURN_IV, XSRETURN_NO, XSRETURN_NV, XSRETURN_PV,
+XSRETURN_UNDEF, XSRETURN_YES, XST_mIV, XST_mNO, XST_mNV, XST_mPV,
+XST_mUNDEF, XST_mYES, XS_VERSION, XS_VERSION_BOOTCHECK, Zero
 
 =item AUTHORS
 
@@ -3941,7 +3960,8 @@ Zero
 =item DESCRIPTION
 
 djSP, is_gv_magical, LVRET, PL_DBsingle, PL_DBsub, PL_DBtrace, PL_dowarn,
-PL_last_in_gv, PL_ofs_sv, PL_rs, start_glob
+PL_last_in_gv, PL_ofs_sv, PL_rs, report_uninit, start_glob, sv_add_arena,
+sv_clean_all, sv_clean_objs, sv_free_arenas
 
 =item AUTHORS
 
@@ -4067,6 +4087,8 @@ PerlIO_apply_layers(f,mode,layers), PerlIO_binmode(f,ptype,imode,layers),
 
 =item Eliminate need for "use utf8";
 
+=item Create a char *sv_printify(sv, STRLEN *lenp, UV flags) function
+
 =item Autoload byte.pm
 
 =item Make "\u{XXXX}" et al work
@@ -4397,6 +4419,8 @@ PerlIO_apply_layers(f,mode,layers), PerlIO_binmode(f,ptype,imode,layers),
 
 =item Lazy evaluation / tail recursion removal
 
+=item Make "use utf8" the default
+
 =back
 
 =back
diff --git a/pod/perlutil.pod b/pod/perlutil.pod
index 293a1bb1d9..93b9e0b51d 100644
--- a/pod/perlutil.pod
+++ b/pod/perlutil.pod
@@ -15,11 +15,6 @@ if appropriate.
 
 =over 3
 
-=item L<libnetcfg|libnetcfg>
-
-Starting from Perl 5.8 the libnet has been part of the standard
-distribution.  To configure libnet run the libnetcfg command.
-
 =item L<perldoc|perldoc>
 
 The main interface to Perl's documentation is C<perldoc>, although
@@ -128,6 +123,16 @@ As well as these filters for converting other languages, the
 L<pl2pm|pl2pm> utility will help you convert old-style Perl 4 libraries to 
 new-style Perl5 modules.
 
+=head2 Administration
+
+=over 3
+
+=item L<libnetcfg|libnetcfg>
+
+To display and change the libnet configuration run the libnetcfg command.
+
+=back
+
 =head2 Development
 
 There are a set of utilities which help you in developing Perl programs, 
diff --git a/utils/libnetcfg.PL b/utils/libnetcfg.PL
index 3418dd11a3..8af49912fe 100644
--- a/utils/libnetcfg.PL
+++ b/utils/libnetcfg.PL
@@ -35,14 +35,74 @@ $Config{startperl}
 
 print OUT <<'!NO!SUBS!';
 
+=head1 NAME
+
+libnetcfg - configure libnet
+
+=head1 DESCRIPTION
+
+The libnetcfg utility can be be used to configure the libnet.
+Starting from perl 5.8 libnet is part of the standard Perl
+distribution, but the libnetcfg can be be used for any libnet
+installation.
+
+=head1 USAGE
+
+Without arguments libnetcfg displays the current configuration.
+
+    $ libnetcfg
+    # old config ./libnet.cfg
+    daytime_hosts        ntp1.none.such
+    ftp_int_passive      0
+    ftp_testhost         ftp.funet.fi
+    inet_domain          none.such
+    nntp_hosts           nntp.none.such
+    ph_hosts             
+    pop3_hosts           pop.none.such
+    smtp_hosts           smtp.none.such
+    snpp_hosts           
+    test_exist           1
+    test_hosts           1
+    time_hosts           ntp.none.such
+    # ./libnetcfg5.7.1 -h for help
+    $ 
+
+It tells where the old configuration file was found (if found).
+
+The C<-h> option will show a usage message.
+
+To change the configuration you will need to use either the C<-c> or
+the C<-d> options.
+
+The default name of the old configuration file is by default
+"libnet.cfg", unless otherwise specified using the -i option, and it
+is searched from your module path, C<-i oldfile>.
+
+The default name of new configuration file is "libnet.cfg", and by
+default it is written to the current directory, unless otherwise
+specified using the -o option, C<-o newfile>.
+
+=head1 SEE ALSO
+
+L<Net::Config>, L<Net::libnetFAQ>
+
+=head1 AUTHORS
+
+Graham Barr, the original Configure script of libnet.
+
+Jarkko Hietaniemi, conversion into libnet cfg for inclusion into Perl 5.8.
+
+=cut
+
 # $Id: Configure,v 1.8 1997/03/04 09:22:32 gbarr Exp $
 
 use strict;
 use IO::File;
 use Getopt::Std;
 use ExtUtils::MakeMaker qw(prompt);
+use File::Spec;
 
-use vars qw($opt_d $opt_o);
+use vars qw($opt_d $opt_c $opt_h $opt_o $opt_i);
 
 ##
 ##
@@ -51,7 +111,7 @@ use vars qw($opt_d $opt_o);
 my %cfg = ();
 my @cfg = ();
 
-my($libnet_cfg,$msg,$ans,$def,$have_old);
+my($libnet_cfg_in,$libnet_cfg_out,$msg,$ans,$def,$have_old);
 
 ##
 ##
@@ -268,17 +328,20 @@ sub default_hostname
 ##
 ##
 
-getopts('do:');
+getopts('dcho:i:');
+
+$libnet_cfg_in = "libnet.cfg"
+	unless(defined($libnet_cfg_in  = $opt_i));
 
-$libnet_cfg = "libnet.cfg"
-	unless(defined($libnet_cfg = $opt_o));
+$libnet_cfg_out = "libnet.cfg"
+	unless(defined($libnet_cfg_out = $opt_o));
 
 my %oldcfg = ();
 
 $Net::Config::CONFIGURE = 1; # Suppress load of user overrides
-if( -f $libnet_cfg )
+if( -f $libnet_cfg_in )
  {
-  %oldcfg = ( %{ do $libnet_cfg } );
+  %oldcfg = ( %{ do $libnet_cfg_in } );
  }
 elsif (eval { require Net::Config }) 
  {
@@ -288,6 +351,59 @@ elsif (eval { require Net::Config })
 
 map { $cfg{lc $_} = $cfg{$_}; delete $cfg{$_} if /[A-Z]/ } keys %cfg;
 
+#---------------------------------------------------------------------------
+
+if ($opt_h) {
+ print <<EOU;
+$0: Usage: $0 [-c] [-d] [-i oldconfigile] [-o newconfigfile] [-h]
+Without options, the old configuration is shown.
+
+   -c change the configuration
+   -d use defaults from the old config (implies -c, non-interactive)
+   -i use a specific file as the old config file
+   -o use a specific file as the new config file
+   -h show this help
+
+The default name of the old configuration file is by default
+"libnet.cfg", unless otherwise specified using the -i option, and it
+is searched from your module path.
+
+The default name of new configuration file is "libnet.cfg", and by
+default it is written to the current directory, unless otherwise
+specified using the -o option.
+
+EOU
+ exit(0);
+}
+
+#---------------------------------------------------------------------------
+
+{
+   my $oldcfgfile;
+   my @inc;
+   push @inc, $ENV{PERL5LIB} if exists $ENV{PERL5LIB};
+   push @inc, $ENV{PERLLIB}  if exists $ENV{PERLLIB};
+   push @inc, @INC;
+   for (@inc) {
+    my $trycfgfile = File::Spec->catfile($_, $libnet_cfg_in);
+    if (-f $trycfgfile && -r $trycfgfile) {
+     $oldcfgfile = $trycfgfile;
+     last;
+    }
+   }
+   print "# old config $oldcfgfile\n" if defined $oldcfgfile;
+   for (sort keys %oldcfg) {
+	printf "%-20s %s\n", $_,
+               ref $oldcfg{$_} ? @{$oldcfg{$_}} : $oldcfg{$_};
+   }
+   unless ($opt_c || $opt_d) {
+    print "# $0 -h for help\n";
+    exit(0);
+   }
+}
+
+#---------------------------------------------------------------------------
+
 $oldcfg{'test_exist'} = 1 unless exists $oldcfg{'test_exist'};
 $oldcfg{'test_hosts'} = 1 unless exists $oldcfg{'test_hosts'};
 
@@ -595,10 +711,10 @@ print "\n";
 
 #---------------------------------------------------------------------------
 
-my $fh = IO::File->new($libnet_cfg, "w") or
-	die "Cannot create `$libnet_cfg': $!";
+my $fh = IO::File->new($libnet_cfg_out, "w") or
+	die "Cannot create `$libnet_cfg_out': $!";
 
-print "Writing $libnet_cfg\n";
+print "Writing $libnet_cfg_out\n";
 
 print $fh "{\n";