[inseparable changes from match from perl-5.003_93 to perl-5.003_94]

 BUILD PROCESS

Subject: Don't use db 2.x, we're not yet ready for it
From: Paul Marquess <pmarquess@bfsec.bt.co.uk>
Files: Configure

Subject: Warn if #! command is longer than 32 chars
From: Chip Salzenberg <chip@perl.com>
Files: Configure

Subject: patches re perl -wc install{perl,man}
Date: Tue, 11 Mar 97 13:13:16 GMT
From: Robin Barker <rmb1@cise.npl.co.uk>
Files: installman installperl

    I got the new installhtml from CPAN
    (TOMC/scripts/pod2html-v2.0beta.shar.gz)
    
    I had problems getting the system call to splitpod at line 376 to work.
    
    1. splitroot was not being found
    2. splitroot was not finding its library
    3. I changed htmlroot to podroot at line 175 to match the documentation.
    
    p5p-msgid: 3180.9703270906@tempest.cise.npl.co.uk
    private-msgid: 21544.9703111313@tempest.cise.npl.co.uk

Subject: 3_93 doesn't install pods
Date: Sun, 16 Mar 1997 02:21:35 -0500
From: Spider Boardman <spider@orb.nashua.nh.us>
Files: installperl
Msg-ID: 199703160721.CAA08339@Orb.Nashua.NH.US

    (applied based on p5p patch as commit 43506a616735d616e03d277d64fbae1e864024bf)

Subject: When installing, use File::Copy instead of `cp`
From: Chip Salzenberg <chip@perl.com>
Files: installperl

Subject: Make hint files' warnings more visible
Date: Thu, 20 Mar 1997 23:18:03 +0100 (MET)
From: Hallvard B Furuseth <h.b.furuseth@usit.uio.no>
Files: hints/3b1.sh hints/apollo.sh hints/cxux.sh hints/dcosx.sh hints/dgux.sh hints/esix4.sh hints/freebsd.sh hints/hpux.sh hints/irix_4.sh hints/mips.sh hints/next_3_0.sh hints/os2.sh hints/qnx.sh hints/sco_2_3_3.sh hints/sco_2_3_4.sh hints/solaris_2.sh hints/ultrix_4.sh hints/utekv.sh

    private-msgid: 199703202218.XAA09041@bombur2.uio.no

 CORE LANGUAGE CHANGES

Subject: Defer creation of array and hash elements as parameters
From: Chip Salzenberg <chip@perl.com>
Files: dump.c global.sym mg.c op.c op.h perl.h pp.c pp_hot.c proto.h sv.c

Subject: New special literal: __PACKAGE__
From: Chip Salzenberg <chip@perl.com>
Files: keywords.pl pod/perldata.pod toke.c

Subject: Abort compilation at C<BEGIN{}> or C<use> after errors
From: Chip Salzenberg <chip@perl.com>
Files: op.c pod/perldiag.pod t/pragma/subs.t

Subject: allow C<substr 'hello', -10>
Date: Mon, 10 Mar 1997 15:55:44 -0800
From: David Dyck <dcd@tc.fluke.com>
Files: pp.c
Msg-ID: 97Mar10.155517pst.35716-2@gateway.fluke.com

    (applied based on p5p patch as commit 77f720bf92f3d0100352416caeedd57936807ff2)

Subject: Regularize C<x % y>, esp. when y is negative
From: Chip Salzenberg <chip@perl.com>
Files: pp.c

Subject: Flush before C<flock(FOO, LOCK_UN)>
From: Chip Salzenberg <chip@perl.com>
Files: pod/perldelta.pod pod/perlfunc.pod pp_sys.c

Subject: Close loopholes in prototype mismatch warning
From: Chip Salzenberg <chip@perl.com>
Files: op.c sv.c toke.c

Subject: Warn on C<while ($x = each %y) {}>
From: Chip Salzenberg <chip@perl.com>
Files: op.c pod/perldiag.pod

Subject: Don't warn on C<print $fh func()>
From: Chip Salzenberg <chip@perl.com>
Files: toke.c

 CORE PORTABILITY

Subject: Don't say 'static var = 1'
Date: Sun, 9 Mar 1997 15:19:57 +0200 (EET)
From: Jarkko Hietaniemi <jhi@iki.fi>
Files: malloc.c

    private-msgid: 199703091319.PAA24714@alpha.hut.fi

Subject: HP/UX hint comments
Date: Fri, 21 Mar 1997 15:43:07 -0500 (EST)
From: Andy Dougherty <doughera@fractal.phys.lafayette.edu>
Files: hints/hpux.sh

    private-msgid: Pine.SOL.3.95q.970321153918.28770B-100000@fractal.lafayette.

Subject: VMS update
Date: Tue, 11 Mar 1997 22:00:55 -0500 (EST)
From: Charles Bailey <bailey@hmivax.humgen.upenn.edu>
Files: lib/ExtUtils/MM_VMS.pm lib/Test/Harness.pm t/op/taint.t utils/perlbug.PL vms/descrip.mms
Msg-ID: 1997Mar11.220056.1873182@hmivax.humgen.upenn.edu

    (applied based on p5p patch as commit 2b5725676da60b49978f38b85bb7f8ee20b4cb55)

Subject: vmsish.t and related patches
Date: Fri, 21 Mar 1997 01:32:47 -0500 (EST)
From: Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>
Files: MANIFEST perl.h vms/descrip.mms vms/ext/vmsish.t vms/vms.c

    private-msgid: 01IGQW3IP1KK005VFB@hmivax.humgen.upenn.edu

Subject: Win32 update (four patches)
From: Gurusamy Sarathy <gsar@engin.umich.edu>
Files: MANIFEST README.win32 lib/AutoSplit.pm lib/Cwd.pm lib/ExtUtils/Command.pm lib/ExtUtils/Install.pm lib/ExtUtils/MM_OS2.pm lib/ExtUtils/MM_Unix.pm lib/ExtUtils/MM_Win32.pm lib/ExtUtils/MakeMaker.pm lib/ExtUtils/Mksymlists.pm lib/File/Basename.pm lib/File/Path.pm mg.c t/comp/cpp.t t/comp/script.t t/harness t/io/argv.t t/io/dup.t t/io/fs.t t/io/inplace.t t/lib/filehand.t t/lib/io_dup.t t/lib/io_sel.t t/lib/io_taint.t t/op/closure.t t/op/exec.t t/op/glob.t t/op/goto.t t/op/magic.t t/op/misc.t t/op/rand.t t/op/split.t t/op/stat.t t/op/sysio.t t/op/taint.t t/pragma/strict.t t/pragma/subs.t t/pragma/warning.t util.c win32/*

 DOCUMENTATION

Subject: perlfaq.pod
Date: Mon, 17 Mar 1997 16:01:40 -0700
From: Tom Christiansen <tchrist@jhereg.perl.com>
Files: MANIFEST pod/Makefile pod/buildtoc pod/perl.pod pod/perlfaq*.pod pod/roffitall

    private-msgid: 199703172301.QAA12566@jhereg.perl.com

Subject: *.pod changes based on the FAQ
Date: Mon, 17 Mar 1997 09:50:14 -0700 (MST)
From: Nat Torkington <gnat@frii.com>
Files: pod/perldata.pod pod/perlfunc.pod pod/perlipc.pod pod/perlop.pod pod/perlre.pod pod/perlrun.pod pod/perlsec.pod pod/perlvar.pod
Msg-ID: 199703171650.JAA02655@elara.frii.com

    (applied based on p5p patch as commit 3c10ad8e31f7d77e71c048b1746912f41cb540f0)

Subject: Document that $. is not reset on implicit open
From: Chip Salzenberg <chip@perl.com>
Files: pod/perldelta.pod

Subject: Re: Embedding success with _93 
Date: Tue, 11 Mar 1997 17:55:05 -0500
From: Doug MacEachern <dougm@opengroup.org>
Files: pod/perldelta.pod
Msg-ID: 199703112255.RAA22775@postman.osf.org

    (applied based on p5p patch as commit 63a6ff3a1dc8d86edb4d8a7ec1548205e32a7114)

Subject: Patch to document illegal characters
Date: Fri, 14 Mar 1997 09:08:10 -0800 (PST)
From: Tom Phoenix <rootbeer@teleport.com>
Files: pod/perldiag.pod pod/perltrap.pod

    private-msgid: Pine.GSO.3.96.970314090558.15346J-100000@kelly.teleport.com

Subject: Document trap with //o and closures
Date: Mon, 10 Mar 1997 18:08:08 -0500 (EST)
From: Charles Bailey <bailey@HMIVAX.HUMGEN.UPENN.EDU>
Files: pod/perltrap.pod
Msg-ID: 01IGCHWRNSEU00661G@hmivax.humgen.upenn.edu

    (applied based on p5p patch as commit a54cb1465fdb400848f23705a6f130bb5c34ab70)

Subject: Illegal character in input
Date: Mon, 10 Mar 1997 15:21:21 -0800 (PST)
From: Tom Phoenix <rootbeer@teleport.com>
Files: pod/perldiag.pod

    private-msgid: Pine.GSO.3.95q.970310151512.22489a-100000@kelly.teleport.com

Subject: Patch for docs Re: Lost backslash
Date: Wed, 19 Mar 1997 07:28:57 -0800 (PST)
From: Tom Phoenix <rootbeer@teleport.com>
Files: pod/perlop.pod

    private-msgid: Pine.GSO.3.96.970319071438.24834G-100000@kelly.teleport.com

Subject: XSUB's doc fix
Date: Mon, 10 Mar 1997 11:42:06 -0500
From: Roderick Schertler <roderick@argon.org>
Files: pod/perlcall.pod pod/perlguts.pod pod/perlxstut.pod
Msg-ID: 28804.858012126@eeyore.ibcinc.com

    (applied based on p5p patch as commit 5f43237038ea7a4151d3bf65aeeecd56ceb78a6a)

Subject: Document return from do FILE
Date: Tue, 18 Mar 1997 14:50:10 +0000
From: "M.J.T. Guy" <mjtg@cus.cam.ac.uk>
Files: pod/perlfunc.pod
Msg-ID: E0w70DK-0001yJ-00@ursa.cus.cam.ac.uk

    (applied based on p5p patch as commit ba8d5fb439878113de8abc9b52d2af237d30fb3c)

Subject: Document $^M in perlvar
Date: Thu, 20 Mar 97 21:08:33 GMT
From: Robin Barker <rmb1@cise.npl.co.uk>
Files: pod/perlvar.pod

    private-msgid: 6153.9703202108@tempest.cise.npl.co.uk

Subject: typos in pods of 5.003_93
Date: 19 Mar 1997 10:39:38 -0600
From: Jim Meyering <meyering@asic.sc.ti.com>
Files: pod/perlfunc.pod pod/perlguts.pod pod/perlre.pod pod/perltoot.pod pod/perlxs.pod
Msg-ID: wpgendbzvhx.fsf@asic.sc.ti.com

    (applied based on p5p patch as commit 76a9873e006cf8f48f57062b2a0dd40b5ed45a95)

Subject: Re: Updates to pod punctuations
Date: Fri, 14 Mar 1997 17:00:12 -0500
From: Larry W. Virden <lvirden@cas.org>
Files: pod/*.pod

    private-msgid: 9703141700.AA22911@cas.org

Subject: clarify example in perlfunc
Date: Thu, 20 Mar 1997 19:46:01 +0200 (EET)
From: Jarkko Hietaniemi <jhi@iki.fi>
Files: pod/perlfunc.pod

    private-msgid: 199703201746.TAA25195@alpha.hut.fi

Subject: Regularize headings in DB_File documentation
From: Chip Salzenberg <chip@perl.com>
Files: ext/DB_File/DB_File.pm

 LIBRARY AND EXTENSIONS

Subject: New module: autouse.pm
Date: Thu, 20 Mar 1997 19:34:30 -0500 (EST)
From: Ilya Zakharevich <ilya@math.ohio-state.edu>
Files: MANIFEST lib/autouse.pm
Msg-ID: 199703210034.TAA13469@monk.mps.ohio-state.edu

    (applied based on p5p patch as commit 6757905eccb6dd0440ef65e8128a277a20f7d943)

Subject: Refresh DB_File to 1.12
Date: Wed, 12 Mar 97 15:51:14 GMT
From: Paul Marquess <pmarquess@bfsec.bt.co.uk>
Files: ext/DB_File/DB_File.pm ext/DB_File/DB_File.xs
Msg-ID: 9703121551.AA07435@claudius.bfsec.bt.co.uk

    (applied based on p5p patch as commit b3deed9189f963e9994815307931f9084f60d1d9)

Subject: In File::Path, some systems can't remove read-only files
From: Chip Salzenberg <chip@perl.com>
Files: lib/File/Path.pm

Subject: Fix bugs revealed by prototype warnings
From: Chip Salzenberg <chip@perl.com>
Files: ext/Opcode/Opcode.pm lib/ExtUtils/MakeMaker.pm lib/Getopt/Long.pm

Subject: Problems with SKIP in makemaker
Date: Thu, 20 Mar 1997 23:13:31 -0500 (EST)
From: Ilya Zakharevich <ilya@math.ohio-state.edu>
Files: lib/ExtUtils/MM_Unix.pm
Msg-ID: 199703210413.XAA21601@monk.mps.ohio-state.edu

    (applied based on p5p patch as commit 970322a2e8024294ada6e8d1a027cb98f1f48ee3)

Subject: In Exporter, don't C<require Carp> at file scope
From: Chip Salzenberg <chip@perl.com>
Files: lib/Exporter.pm

Subject: fix for Exporter's $SIG{__WARN__} handler
Date: Thu, 13 Mar 1997 18:40:51 -0500
From: Roderick Schertler <roderick@argon.org>
Files: lib/Exporter.pm
Msg-ID: 2282.858296451@eeyore.ibcinc.com

    (applied based on p5p patch as commit 2768ea1aeef34f42d096f198fbe629c8374ca429)

Subject: Don't try to substr() refs in Carp
From: Chip Salzenberg <chip@perl.com>
Files: lib/Carp.pm

Subject: Re: NUL in die and other messages
Date: Fri, 21 Mar 1997 09:58:17 +0000
From: "M.J.T. Guy" <mjtg@cus.cam.ac.uk>
Files: lib/Carp.pm
Msg-ID: E0w815V-0005xs-00@ursa.cus.cam.ac.uk

    (applied based on p5p patch as commit 52a267c574cb66c4bc35601dcf148a1d7a3bc557)

 OTHER CORE CHANGES

Subject: Guard against buffer overflow in yyerror() and related funcs
From: Chip Salzenberg <chip@perl.com>
Files: toke.c

Subject: For bin compat, rename calllist() and he_{,delay}free
From: Chip Salzenberg <chip@perl.com>
Files: global.sym hv.c op.c perl.c pod/perlguts.pod proto.h

Subject: Fix C<print> on tied default handle
From: Chip Salzenberg <chip@perl.com>
Files: pp_hot.c

Subject: Fix C<local($a, undef, $b) = (1,2,3)>
From: Chip Salzenberg <chip@perl.com>
Files: op.c

Subject: Improve diagnostic on C<@a++>, C<--%a>, @a =~ s/a/b/
From: Chip Salzenberg <chip@perl.com>
Files: pp.c pp_hot.c

Subject: Don't warn on C<$x{y} .= "z"> when %x is tied
From: Chip Salzenberg <chip@perl.com>
Files: pp_hot.c

Subject: Eliminate 'unreachable code' warnings
From: Chip Salzenberg <chip@perl.com>
Files: ext/POSIX/POSIX.xs mg.c pp_ctl.c toke.c

Subject: printf format corrections for -DDEBUGGING
Date: Wed, 19 Mar 1997 12:42:50 -0500
From: Roderick Schertler <roderick@argon.org>
Files: doop.c malloc.c op.c pp_ctl.c regexec.c sv.c x2p/str.c x2p/util.c
Msg-ID: 26592.858793370@eeyore.ibcinc.com

    (applied based on p5p patch as commit e125f273e351a19a92b69d6244af55abbbf0a26d)

Subject: Warn about missing -DMULTIPLICITY if likely a problem
Date: Wed, 19 Mar 1997 18:45:53 -0500
From: Doug MacEachern <dougm@opengroup.org>
Files: perl.c
Msg-ID: 199703192345.SAA15070@postman.osf.org

    (applied based on p5p patch as commit 71aeea1753924e6e19c2461e241e3f7d8a570e90)

1 files changed, 749 insertions, 0 deletions

diff --git a/pod/perlfaq8.pod b/pod/perlfaq8.pod
new file mode 100644
index 0000000000..6ad5c15750
--- /dev/null
+++ b/pod/perlfaq8.pod
@@ -0,0 +1,749 @@
+=head1 NAME
+
+perlfaq8 - System Interaction ($Revision: 1.15 $)
+
+=head1 DESCRIPTION
+
+This section of the Perl FAQ covers questions involving operating
+system interaction.  This involves interprocess communication (IPC),
+control over the user-interface (keyboard, screen and pointing
+devices), and most anything else not related to data manipulation.
+
+Read the FAQs and documentation specific to the port of perl to your
+operating system (eg, L<perlvms>, L<perlplan9>, ...).  These should
+contain more detailed information on the vagaries of your perl.
+
+=head2 How do I find out which operating system I'm running under?
+
+The $^O variable ($OSTYPE if you use English) contains the operating
+system that your perl binary was built for.
+
+=head2 How come exec() doesn't return?
+
+Because that's what it does: it replaces your currently running
+program with a different one.  If you want to keep going (as is
+probably the case if you're asking this question) use system()
+instead.
+
+=head2 How do I do fancy stuff with the keyboard/screen/mouse?
+
+How you access/control keyboards, screens, and pointing devices
+("mice") is system-dependent.  Try the following modules:
+
+=over 4
+
+=item Keyboard
+
+    Term::Cap			Standard perl distribution
+    Term::ReadKey		CPAN
+    Term::ReadLine::Gnu		CPAN
+    Term::ReadLine::Perl	CPAN
+    Term::Screen		CPAN
+
+=item Screen
+
+    Term::Cap			Standard perl distribution
+    Curses			CPAN
+    Term::ANSIColor		CPAN
+
+=item Mouse
+
+    Tk				CPAN
+
+=back
+
+=head2 How do I ask the user for a password?
+
+(This question has nothing to do with the web.  See a different
+FAQ for that.)
+
+There's an example of this in L<perlfunc/crypt>).  First, you put
+the terminal into "no echo" mode, then just read the password
+normally.  You may do this with an old-style ioctl() function, POSIX
+terminal control (see L<POSIX>, and Chapter 7 of the Camel), or a call
+to the B<stty> program, with varying degrees of portability.
+
+You can also do this for most systems using the Term::ReadKey module
+from CPAN, which is easier to use and in theory more portable.
+
+=head2 How do I read and write the serial port?
+
+This depends on which operating system your program is running on.  In
+the case of Unix, the serial ports will be accessible through files in
+/dev; on other systems, the devices names will doubtless differ.
+Several problem areas common to all device interaction are the
+following
+
+=over 4
+
+=item lockfiles
+
+Your system may use lockfiles to control multiple access.  Make sure
+you follow the correct protocol.  Unpredictable behaviour can result
+from multiple processes reading from one device.
+
+=item open mode
+
+If you expect to use both read and write operations on the device,
+you'll have to open it for update (see L<perlfunc/"open"> for
+details).  You may wish to open it without running the risk of
+blocking by using sysopen() and C<O_RDWR|O_NDELAY|O_NOCTTY> from the
+Fcntl module (part of the standard perl distribution).  See
+L<perlfunc/"sysopen"> for more on this approach.
+
+=item end of line
+
+Some devices will be expecting a "\r" at the end of each line rather
+than a "\n".  In some ports of perl, "\r" and "\n" are different from
+their usual (Unix) ASCII values of "\012" and "\015".  You may have to
+give the numeric values you want directly, using octal ("\015"), hex
+("0x0D"), or as a control-character specification ("\cM").
+
+    print DEV "atv1\012";	# wrong, for some devices
+    print DEV "atv1\015";	# right, for some devices
+
+Even though with normal text files, a "\n" will do the trick, there is
+still no unified scheme for terminating a line that is portable
+between Unix, DOS/Win, and Macintosh, except to terminate I<ALL> line
+ends with "\015\012", and strip what you don't need from the output.
+This applies especially to socket I/O and autoflushing, discussed
+next.
+
+=item flushing output
+
+If you expect characters to get to your device when you print() them,
+you'll want to autoflush that filehandle, as in the older
+
+    use FileHandle;
+    DEV->autoflush(1);
+
+and the newer
+
+    use IO::Handle;
+    DEV->autoflush(1);
+
+You can use select() and the C<$|> variable to control autoflushing
+(see L<perlvar/$|> and L<perlfunc/select>):
+
+    $oldh = select(DEV);
+    $| = 1;
+    select($oldh);
+
+You'll also see code that does this without a temporary variable, as in
+
+    select((select(DEV), $| = 1)[0]);
+
+As mentioned in the previous item, this still doesn't work when using
+socket I/O between Unix and Macintosh.  You'll need to hardcode your
+line terminators, in that case.
+
+=item non-blocking input
+
+If you are doing a blocking read() or sysread(), you'll have to
+arrange for an alarm handler to provide a timeout (see
+L<perlfunc/alarm>).  If you have a non-blocking open, you'll likely
+have a non-blocking read, which means you may have to use a 4-arg
+select() to determine whether I/O is ready on that device (see
+L<perlfunc/"select">.
+
+=back
+
+=head2 How do I decode encrypted password files?
+
+You spend lots and lots of money on dedicated hardware, but this is
+bound to get you talked about.
+
+Seriously, you can't if they are Unix password files - the Unix
+password system employs one-way encryption.  Programs like Crack can
+forcibly (and intelligently) try to guess passwords, but don't (can't)
+guarantee quick success.
+
+If you're worried about users selecting bad passwords, you should
+proactively check when they try to change their password (by modifying
+passwd(1), for example).
+
+=head2 How do I start a process in the background?
+
+You could use
+
+    system("cmd &")
+
+or you could use fork as documented in L<perlfunc/"fork">, with
+further examples in L<perlipc>.  Some things to be aware of, if you're
+on a Unix-like system:
+
+=over 4
+
+=item STDIN, STDOUT and STDERR are shared
+
+Both the main process and the backgrounded one (the "child" process)
+share the same STDIN, STDOUT and STDERR filehandles.  If both try to
+access them at once, strange things can happen.  You may want to close
+or reopen these for the child.  You can get around this with
+C<open>ing a pipe (see L<perlfunc/"open">) but on some systems this
+means that the child process cannot outlive the parent.
+
+=item Signals
+
+You'll have to catch the SIGCHLD signal, and possibly SIGPIPE too.
+SIGCHLD is sent when the backgrounded process finishes.  SIGPIPE is
+sent when you write to a filehandle whose child process has closed (an
+untrapped SIGPIPE can cause your program to silently die).  This is
+not an issue with C<system("cmd&")>.
+
+=item Zombies
+
+You have to be prepared to "reap" the child process when it finishes
+
+    $SIG{CHLD} = sub { wait };
+
+See L<perlipc/"Signals"> for other examples of code to do this.
+Zombies are not an issue with C<system("prog &")>.
+
+=back
+
+=head2 How do I trap control characters/signals?
+
+You don't actually "trap" a control character.  Instead, that
+character generates a signal, which you then trap.  Signals are
+documented in L<perlipc/"Signals"> and chapter 6 of the Camel.
+
+Be warned that very few C libraries are re-entrant.  Therefore, if you
+attempt to print() in a handler that got invoked during another stdio
+operation your internal structures will likely be in an
+inconsistent state, and your program will dump core.  You can
+sometimes avoid this by using syswrite() instead of print().
+
+Unless you're exceedingly careful, the only safe things to do inside a
+signal handler are: set a variable and exit.  And in the first case,
+you should only set a variable in such a way that malloc() is not
+called (eg, by setting a variable that already has a value).
+
+For example:
+
+    $Interrupted = 0;	# to ensure it has a value
+    $SIG{INT} = sub {
+        $Interrupted++;
+	syswrite(STDERR, "ouch\n", 5);
+    }
+
+However, because syscalls restart by default, you'll find that if
+you're in a "slow" call, such as E<lt>FHE<gt>, read(), connect(), or
+wait(), that the only way to terminate them is by "longjumping" out;
+that is, by raising an exception.  See the time-out handler for a
+blocking flock() in L<perlipc/"Signals"> or chapter 6 of the Camel.
+
+=head2 How do I modify the shadow password file on a Unix system?
+
+If perl was installed correctly, the getpw*() functions described in
+L<perlfunc> provide (read-only) access to the shadow password file.
+To change the file, make a new shadow password file (the format varies
+from system to system - see L<passwd(5)> for specifics) and use
+pwd_mkdb(8) to install it (see L<pwd_mkdb(5)> for more details).
+
+=head2 How do I set the time and date?
+
+Assuming you're running under sufficient permissions, you should be
+able to set the system-wide date and time by running the date(1)
+program.  (There is no way to set the time and date on a per-process
+basis.)  This mechanism will work for Unix, MS-DOS, Windows, and NT;
+the VMS equivalent is C<set time>.
+
+However, if all you want to do is change your timezone, you can
+probably get away with setting an environment variable:
+
+    $ENV{TZ} = "MST7MDT";		   # unixish
+    $ENV{'SYS$TIMEZONE_DIFFERENTIAL'}="-5" # vms
+    system "trn comp.lang.perl";
+
+=head2 How can I sleep() or alarm() for under a second?
+
+If you want finer granularity than the 1 second that the sleep()
+function provides, the easiest way is to use the select() function as
+documented in L<perlfunc/"select">.  If your system has itimers and
+syscall() support, you can check out the old example in
+http://www.perl.com/CPAN/doc/misc/ancient/tutorial/eg/itimers.pl .
+
+=head2 How can I measure time under a second?
+
+In general, you may not be able to.  The Time::HiRes module (available
+from CPAN) provides this functionality for some systems.   
+
+In general, you may not be able to.  But if you system supports both the
+syscall() function in Perl as well as a system call like gettimeofday(2),
+then you may be able to do something like this:
+
+    require 'sys/syscall.ph';
+
+    $TIMEVAL_T = "LL";
+
+    $done = $start = pack($TIMEVAL_T, ());
+
+    syscall( &SYS_gettimeofday, $start, 0)) != -1
+               or die "gettimeofday: $!";
+
+       ##########################
+       # DO YOUR OPERATION HERE #
+       ##########################
+
+    syscall( &SYS_gettimeofday, $done, 0) != -1
+           or die "gettimeofday: $!";
+
+    @start = unpack($TIMEVAL_T, $start);
+    @done  = unpack($TIMEVAL_T, $done);
+
+    # fix microseconds
+    for ($done[1], $start[1]) { $_ /= 1_000_000 }
+
+    $delta_time = sprintf "%.4f", ($done[0]  + $done[1]  )
+                                            -
+                                 ($start[0] + $start[1] );
+
+=head2 How can I do an atexit() or setjmp()/longjmp()? (Exception handling)
+
+Release 5 of Perl added the END block, which can be used to simulate
+atexit().  Each package's END block is called when the program or
+thread ends (see L<perlmod> manpage for more details).  It isn't
+called when untrapped signals kill the program, though, so if you use
+END blocks you should also use
+
+	use sigtrap qw(die normal-signals);
+
+Perl's exception-handling mechanism is its eval() operator.  You can
+use eval() as setjmp and die() as longjmp.  For details of this, see
+the section on signals, especially the time-out handler for a blocking
+flock() in L<perlipc/"Signals"> and chapter 6 of the Camel.
+
+If exception handling is all you're interested in, try the
+exceptions.pl library (part of the standard perl distribution).
+
+If you want the atexit() syntax (and an rmexit() as well), try the
+AtExit module available from CPAN.
+
+=head2 Why doesn't my sockets program work under System V (Solaris)? What does the error message "Protocol not supported" mean?
+
+Some Sys-V based systems, notably Solaris 2.X, redefined some of the
+standard socket constants.  Since these were constant across all
+architectures, they were often hardwired into perl code.  The proper
+way to deal with this is to "use Socket" to get the correct values.
+
+Note that even though SunOS and Solaris are binary compatible, these
+values are different.  Go figure.
+
+=head2 How can I call my system's unique C functions from Perl?
+
+In most cases, you write an external module to do it - see the answer
+to "Where can I learn about linking C with Perl? [h2xs, xsubpp]".
+However, if the function is a system call, and your system supports
+syscall(), you can use the syscall function (documented in
+L<perlfunc>).
+
+Remember to check the modules that came with your distribution, and
+CPAN as well - someone may already have written a module to do it.
+
+=head2 Where do I get the include files to do ioctl() or syscall()?
+
+Historically, these would be generated by the h2ph tool, part of the
+standard perl distribution.  This program converts cpp(1) directives
+in C header files to files containing subroutine definitions, like
+&SYS_getitimer, which you can use as arguments to your functions.
+It doesn't work perfectly, but it usually gets most of the job done.
+Simple files like F<errno.h>, F<syscall.h>, and F<socket.h> were fine,
+but the hard ones like F<ioctl.h> nearly always need to hand-edited.
+Here's how to install the *.ph files:
+
+    1.  become super-user
+    2.  cd /usr/include
+    3.  h2ph *.h */*.h
+
+If your system supports dynamic loading, for reasons of portability and
+sanity you probably ought to use h2xs (also part of the standard perl
+distribution).  This tool converts C header files to Perl extensions.
+See L<perlxstut> for how to get started with h2xs.
+
+If your system doesn't support dynamic loading, you still probably
+ought to use h2xs.  See L<perlxstut> and L<ExtUtils::MakeMaker> for
+more information (in brief, just use B<make perl> instead of a plain
+B<make> to rebuild perl with a new static extension).
+
+=head2 Why do setuid perl scripts complain about kernel problems?
+
+Some operating systems have bugs in the kernel that make setuid
+scripts inherently insecure.  Perl gives you a number of options
+(described in L<perlsec>) to work around such systems.
+
+=head2 How can I open a pipe both to and from a command?
+
+The IPC::Open2 module (part of the standard perl distribution) is an
+easy-to-use approach that internally uses pipe(), fork(), and exec()
+to do the job.  Make sure you read the deadlock warnings in its
+documentation, though (see L<IPC::Open2>).
+
+=head2 How can I capture STDERR from an external command?
+
+There are three basic ways of running external commands:
+
+    system $cmd;		# using system()
+    $output = `$cmd`;		# using backticks (``)
+    open (PIPE, "cmd |");	# using open()
+
+With system(), both STDOUT and STDERR will go the same place as the
+script's versions of these, unless the command redirects them.
+Backticks and open() read B<only> the STDOUT of your command.
+
+With any of these, you can change file descriptors before the call:
+
+    open(STDOUT, ">logfile");
+    system("ls");
+
+or you can use Bourne shell file-descriptor redirection:
+
+    $output = `$cmd 2>some_file`;
+    open (PIPE, "cmd 2>some_file |");
+
+You can also use file-descriptor redirection to make STDERR a
+duplicate of STDOUT:
+
+    $output = `$cmd 2>&1`;
+    open (PIPE, "cmd 2>&1 |");
+
+Note that you I<cannot> simply open STDERR to be a dup of STDOUT
+in your Perl program and avoid calling the shell to do the redirection.
+This doesn't work:
+
+    open(STDERR, ">&STDOUT");
+    $alloutput = `cmd args`;  # stderr still escapes
+
+This fails because the open() makes STDERR go to where STDOUT was
+going at the time of the open().  The backticks then make STDOUT go to
+a string, but don't change STDERR (which still goes to the old
+STDOUT).
+
+Note that you I<must> use Bourne shell (sh(1)) redirection syntax in
+backticks, not csh(1)!  Details on why Perl's system() and backtick
+and pipe opens all use the Bourne shell are in
+http://www.perl.com/CPAN/doc/FMTEYEWTK/versus/csh.whynot .
+
+You may also use the IPC::Open3 module (part of the standard perl
+distribution), but be warned that it has a different order of
+arguments from IPC::Open2 (see L<IPC::Open3>).
+
+=head2 Why doesn't open() return an error when a pipe open fails?
+
+It does, but probably not how you expect it to.  On systems that
+follow the standard fork()/exec() paradigm (eg, Unix), it works like
+this: open() causes a fork().  In the parent, open() returns with the
+process ID of the child.  The child exec()s the command to be piped
+to/from.  The parent can't know whether the exec() was successful or
+not - all it can return is whether the fork() succeeded or not.  To
+find out if the command succeeded, you have to catch SIGCHLD and
+wait() to get the exit status.
+
+On systems that follow the spawn() paradigm, open() I<might> do what
+you expect - unless perl uses a shell to start your command. In this
+case the fork()/exec() description still applies.
+
+=head2 What's wrong with using backticks in a void context?
+
+Strictly speaking, nothing.  Stylistically speaking, it's not a good
+way to write maintainable code because backticks have a (potentially
+humungous) return value, and you're ignoring it.  It's may also not be very
+efficient, because you have to read in all the lines of output, allocate
+memory for them, and then throw it away.  Too often people are lulled
+to writing:
+
+    `cp file file.bak`;
+
+And now they think "Hey, I'll just always use backticks to run programs."
+Bad idea: backticks are for capturing a program's output; the system()
+function is for running programs.
+
+Consider this line:
+
+    `cat /etc/termcap`;
+
+You haven't assigned the output anywhere, so it just wastes memory
+(for a little while).  Plus you forgot to check C<$?> to see whether
+the program even ran correctly.  Even if you wrote
+
+    print `cat /etc/termcap`;
+
+In most cases, this could and probably should be written as
+
+    system("cat /etc/termcap") == 0
+	or die "cat program failed!";
+
+Which will get the output quickly (as its generated, instead of only
+at the end ) and also check the return value.
+
+system() also provides direct control over whether shell wildcard
+processing may take place, whereas backticks do not.
+
+=head2 How can I call backticks without shell processing?
+
+This is a bit tricky.  Instead of writing
+
+    @ok = `grep @opts '$search_string' @filenames`;
+
+You have to do this:
+
+    my @ok = ();
+    if (open(GREP, "-|")) {
+        while (<GREP>) {
+	    chomp;
+            push(@ok, $_);
+        }
+	close GREP;
+    } else {
+        exec 'grep', @opts, $search_string, @filenames;
+    }
+
+Just as with system(), no shell escapes happen when you exec() a list.
+
+=head2 Why can't my script read from STDIN after I gave it EOF (^D on Unix, ^Z on MSDOS)?
+
+Because some stdio's set error and eof flags that need clearing.  The
+POSIX module defines clearerr() that you can use.  That is the
+technically correct way to do it.  Here are some less reliable
+workarounds:
+
+=over 4
+
+=item 1
+
+Try keeping around the seekpointer and go there, like this:
+
+    $where = tell(LOG);
+    seek(LOG, $where, 0);
+
+=item 2
+
+If that doesn't work, try seeking to a different part of the file and
+then back.
+
+=item 3
+
+If that doesn't work, try seeking to a different part of
+the file, reading something, and then seeking back.
+
+=item 4
+
+If that doesn't work, give up on your stdio package and use sysread.
+
+=back
+
+=head2 How can I convert my shell script to perl?
+
+Learn Perl and rewrite it.  Seriously, there's no simple converter.
+Things that are awkward to do in the shell are easy to do in Perl, and
+this very awkwardness is what would make a shell->perl converter
+nigh-on impossible to write.  By rewriting it, you'll think about what
+you're really trying to do, and hopefully will escape the shell's
+pipeline datastream paradigm, which while convenient for some matters,
+causes many inefficiencies.
+
+=head2 Can I use perl to run a telnet or ftp session?
+
+Try the Net::FTP and TCP::Client modules (available from CPAN).
+http://www.perl.com/CPAN/scripts/netstuff/telnet.emul.shar will also
+help for emulating the telnet protocol.
+
+=head2 How can I write expect in Perl?
+
+Once upon a time, there was a library called chat2.pl (part of the
+standard perl distribution), which never really got finished.  These
+days, your best bet is to look at the Comm.pl library available from
+CPAN.
+
+=head2 Is there a way to hide perl's command line from programs such as "ps"?
+
+First of all note that if you're doing this for security reasons (to
+avoid people seeing passwords, for example) then you should rewrite
+your program so that critical information is never given as an
+argument.  Hiding the arguments won't make your program completely
+secure.
+
+To actually alter the visible command line, you can assign to the
+variable $0 as documented in L<perlvar>.  This won't work on all
+operating systems, though.  Daemon programs like sendmail place their
+state there, as in:
+
+    $0 = "orcus [accepting connections]";
+
+=head2 I {changed directory, modified my environment} in a perl script.  How come the change disappeared when I exited the script?  How do I get my changes to be visible?
+
+=over 4
+
+=item Unix
+
+In the strictest sense, it can't be done -- the script executes as a
+different process from the shell it was started from.  Changes to a
+process are not reflected in its parent, only in its own children
+created after the change.  There is shell magic that may allow you to
+fake it by eval()ing the script's output in your shell; check out the
+comp.unix.questions FAQ for details.
+
+=item VMS
+
+Change to %ENV persist after Perl exits, but directory changes do not.
+
+=back
+
+=head2 How do I close a process's filehandle without waiting for it to complete?
+
+Assuming your system supports such things, just send an appropriate signal
+to the process (see L<perlfunc/"kill">.  It's common to first send a TERM
+signal, wait a little bit, and then send a KILL signal to finish it off.
+
+=head2 How do I fork a daemon process?
+
+If by daemon process you mean one that's detached (disassociated from
+its tty), then the following process is reported to work on most
+Unixish systems.  Non-Unix users should check their Your_OS::Process
+module for other solutions.
+
+=over 4
+
+=item *
+
+Open /dev/tty and use the the TIOCNOTTY ioctl on it.  See L<tty(4)>
+for details.
+
+=item *
+
+Change directory to /
+
+=item *
+
+Reopen STDIN, STDOUT, and STDERR so they're not connected to the old
+tty.
+
+=item *
+
+Background yourself like this:
+
+    fork && exit;
+
+=back
+
+=head2 How do I make my program run with sh and csh?
+
+See the F<eg/nih> script (part of the perl source distribution).
+
+=head2 How do I keep my own module/library directory?
+
+When you build modules, use the PREFIX option when generating
+Makefiles:
+
+    perl Makefile.PL PREFIX=/u/mydir/perl
+
+then either set the PERL5LIB environment variable before you run
+scripts that use the modules/libraries (see L<perlrun>) or say
+
+    use lib '/u/mydir/perl';
+
+See Perl's L<lib> for more information.
+
+=head2 How do I find out if I'm running interactively or not?
+
+Good question.  Sometimes C<-t STDIN> and C<-t STDOUT> can give clues,
+sometimes not.
+
+    if (-t STDIN && -t STDOUT) {
+	print "Now what? ";
+    }
+
+On POSIX systems, you can test whether your own process group matches
+the current process group of your controlling terminal as follows:
+
+    use POSIX qw/getpgrp tcgetpgrp/;
+    open(TTY, "/dev/tty") or die $!;
+    $tpgrp = tcgetpgrp(TTY);
+    $pgrp = getpgrp();
+    if ($tpgrp == $pgrp) {
+        print "foreground\n";
+    } else {
+        print "background\n";
+    }
+
+=head2 How do I timeout a slow event?
+
+Use the alarm() function, probably in conjunction with a signal
+handler, as documented L<perlipc/"Signals"> and chapter 6 of the
+Camel.  You may instead use the more flexible Sys::AlarmCall module
+available from CPAN.
+
+=head2 How do I set CPU limits?
+
+Use the BSD::Resource module from CPAN.
+
+=head2 How do I avoid zombies on a Unix system?
+
+Use the reaper code from L<perlipc/"Signals"> to call wait() when a
+SIGCHLD is received, or else use the double-fork technique described
+in L<perlfunc/fork>.
+
+=head2 How do I use an SQL database?
+
+There are a number of excellent interfaces to SQL databases.  See the
+DBD::* modules available from
+http://www.perl.com/CPAN/modules/dbperl/DBD .
+
+=head2 How do I make a system() exit on control-C?
+
+You can't.  You need to imitate the system() call (see L<perlipc> for
+sample code) and then have a signal handler for the INT signal that
+passes the signal on to the subprocess.
+
+=head2 How do I open a file without blocking?
+
+If you're lucky enough to be using a system that supports
+non-blocking reads (most Unixish systems do), you need only to use the
+O_NDELAY or O_NONBLOCK flag from the Fcntl module in conjunction with
+sysopen():
+
+    use Fcntl;
+    sysopen(FH, "/tmp/somefile", O_WRONLY|O_NDELAY|O_CREAT, 0644)
+        or die "can't open /tmp/somefile: $!":
+
+=head2 How do I install a CPAN module?
+
+The easiest way is to have the CPAN module do it for you.  This module
+comes with perl version 5.004 and later.  To manually install the CPAN
+module, or any well-behaved CPAN module for that matter, follow these
+steps:
+
+=over 4
+
+=item 1
+
+Unpack the source into a temporary area.
+
+=item 2
+
+    perl Makefile.PL
+
+=item 3
+
+    make
+
+=item 4
+
+    make test
+
+=item 5
+
+    make install
+
+=back
+
+If your version of perl is compiled without dynamic loading, then you
+just need to replace step 3 (B<make>) with B<make perl> and you will
+get a new F<perl> binary with your extension linked in.
+
+See L<ExtUtils::MakeMaker> for more details on building extensions.
+
+=head1 AUTHOR AND COPYRIGHT
+
+Copyright (c) 1997 Tom Christiansen and Nathan Torkington.
+All rights reserved.  See L<perlfaq> for distribution information.