=head1 NAME
-perlfaq8 - System Interaction ($Revision: 1.17 $, $Date: 1997/03/25 18:17:12 $)
+perlfaq8 - System Interaction ($Revision: 1.21 $, $Date: 1997/04/24 22:44:19 $)
=head1 DESCRIPTION
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>, F<REAMDE.os2>, ...). These should
+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?
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, MS-DOS/Windows, and Macintosh, except to terminate I<ALL> line
+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.
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 reentrant. Therefore, if you
+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
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 timeout handler for a
+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?
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
+In general, you may not be able to. But if your 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:
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 timeout handler for a blocking
+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
but the hard ones like F<ioctl.h> nearly always need to hand-edited.
Here's how to install the *.ph files:
- 1. become superuser
+ 1. become super-user
2. cd /usr/include
3. h2ph *.h */*.h
=head2 Why can't I get the output of a command with system()?
-You're confusing the purpose of system() and backticks (''). system()
-runs a command and returns exit status information (as a 16 bit value
--- the low 8 bits are the signal the process died from, if any, and
-the high 8 bits are the actual exit value). Backticks ('') run a
+You're confusing the purpose of system() and backticks (``). system()
+runs a command and returns exit status information (as a 16 bit value:
+the low 8 bits are the signal the process died from, if any, and
+the high 8 bits are the actual exit value). Backticks (``) run a
command and return what it sent to STDOUT.
- $status = system("mail-users");
- $output = `ls`;
+ $exit_status = system("mail-users");
+ $output_string = `ls`;
=head2 How can I capture STDERR from an external command?
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 data stream paradigm, which while convenient for some matters,
+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.
+Try the Net::FTP, TCP::Client, and Net::Telnet modules (available from
+CPAN). http://www.perl.com/CPAN/scripts/netstuff/telnet.emul.shar
+will also help for emulating the telnet protocol, but Net::Telnet is
+quite probably easier to use..
+
+If all you want to do is pretend to be telnet but don't need
+the initial telnet handshaking, then the standard dual-process
+approach will suffice:
+
+ use IO::Socket; # new in 5.004
+ $handle = IO::Socket::INET->new('www.perl.com:80')
+ || die "can't connect to port 80 on www.perl.com: $!";
+ $handle->autoflush(1);
+ if (fork()) { # XXX: undef means failure
+ select($handle);
+ print while <STDIN>; # everything from stdin to socket
+ } else {
+ print while <$handle>; # everything from socket to stdout
+ }
+ close $handle;
+ exit;
=head2 How can I write expect in Perl?
=item *
-Open /dev/tty and use the TIOCNOTTY ioctl on it. See L<tty(4)>
+Open /dev/tty and use the the TIOCNOTTY ioctl on it. See L<tty(4)>
for details.
=item *
See the F<eg/nih> script (part of the perl source distribution).
-=head2 How do I keep my own module/library directory?
-
-When you build modules, use the PREFIX option when generating
-Makefiles:
-
- perl Makefile.PL PREFIX=/u/mydir/perl
-
-then either set the PERL5LIB environment variable before you run
-scripts that use the modules/libraries (see L<perlrun>) or say
-
- use lib '/u/mydir/perl';
-
-See Perl's L<lib> for more information.
-
=head2 How do I find out if I'm running interactively or not?
Good question. Sometimes C<-t STDIN> and C<-t STDOUT> can give clues,
just need to replace step 3 (B<make>) with B<make perl> and you will
get a new F<perl> binary with your extension linked in.
-See L<ExtUtils::MakeMaker> for more details on building extensions.
+See L<ExtUtils::MakeMaker> for more details on building extensions
+and an answer to the question "How do I keep my own module/library
+directory?"
+
+=head2 How do I keep my own module/library directory?
+
+When you build modules, use the PREFIX option when generating
+Makefiles:
+
+ perl Makefile.PL PREFIX=/u/mydir/perl
+
+then either set the PERL5LIB environment variable before you run
+scripts that use the modules/libraries (see L<perlrun>) or say
+
+ use lib '/u/mydir/perl';
+
+See Perl's L<lib> for more information.
+
+=head2 How do I add the directory my program lives in to the module/library search path?
+
+ use FindBin;
+ use lib "$FindBin::Bin";
+ use your_own_modules;
+
+=head2 How do I add a directory to my include path at runtime?
+
+Here are the suggested ways of modifying your include path:
+
+ the PERLLIB environment variable
+ the PERL5LIB environment variable
+ the perl -Idir commpand line flag
+ the use lib pragma, as in
+ use lib "$ENV{HOME}/myown_perllib";
+
+The latter is particularly useful because it knows about machine
+dependent architectures. The lib.pm pragmatic module was first
+included with the 5.002 release of Perl.
+
+=head1 How do I get one key from the terminal at a time, under POSIX?
+
+ #!/usr/bin/perl -w
+ use strict;
+ $| = 1;
+ for (1..4) {
+ my $got;
+ print "gimme: ";
+ $got = getone();
+ print "--> $got\n";
+ }
+ exit;
+
+ BEGIN {
+ use POSIX qw(:termios_h);
+
+ my ($term, $oterm, $echo, $noecho, $fd_stdin);
+
+ $fd_stdin = fileno(STDIN);
+
+ $term = POSIX::Termios->new();
+ $term->getattr($fd_stdin);
+ $oterm = $term->getlflag();
+
+ $echo = ECHO | ECHOK | ICANON;
+ $noecho = $oterm & ~$echo;
+
+ sub cbreak {
+ $term->setlflag($noecho);
+ $term->setcc(VTIME, 1);
+ $term->setattr($fd_stdin, TCSANOW);
+ }
+
+ sub cooked {
+ $term->setlflag($oterm);
+ $term->setcc(VTIME, 0);
+ $term->setattr($fd_stdin, TCSANOW);
+ }
+
+ sub getone {
+ my $key = '';
+ cbreak();
+ sysread(STDIN, $key, 1);
+ cooked();
+ return $key;
+ }
+
+ }
+ END { cooked() }
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997 Tom Christiansen and Nathan Torkington.
-All rights reserved. See L<perlfaq> for distribution information.
+Copyright (c) 1997, 1998 Tom Christiansen and Nathan Torkington.
+All rights reserved.
+
+When included as part of the Standard Version of Perl, or as part of
+its complete documentation whether printed or otherwise, this work
+may be distributed only under the terms of Perl's Artistic License.
+Any distribution of this file or derivatives thereof I<outside>
+of that package require that special arrangements be made with
+copyright holder.
+
+Irrespective of its distribution, all code examples in this file
+are hereby placed into the public domain. You are permitted and
+encouraged to use this code in your own programs for fun
+or for profit as you see fit. A simple comment in the code giving
+credit would be courteous but is not required.
projects / p5sagit/p5-mst-13.2.git / blobdiff