=head1 NAME
-perlfaq8 - System Interaction ($Revision: 1.23 $, $Date: 2005/01/03 18:43:37 $)
+perlfaq8 - System Interaction ($Revision: 3606 $)
=head1 DESCRIPTION
=item Keyboard
- Term::Cap Standard perl distribution
- Term::ReadKey CPAN
- Term::ReadLine::Gnu CPAN
- Term::ReadLine::Perl CPAN
- Term::Screen CPAN
+ Term::Cap Standard perl distribution
+ Term::ReadKey CPAN
+ Term::ReadLine::Gnu CPAN
+ Term::ReadLine::Perl CPAN
+ Term::Screen CPAN
=item Screen
- Term::Cap Standard perl distribution
- Curses CPAN
- Term::ANSIColor CPAN
+ Term::Cap Standard perl distribution
+ Curses CPAN
+ Term::ANSIColor CPAN
=item Mouse
- Tk CPAN
+ Tk CPAN
=back
-Some of these specific cases are shown below.
+Some of these specific cases are shown as examples in other answers
+in this section of the perlfaq.
=head2 How do I print something out in color?
If you expect characters to get to your device when you print() them,
you'll want to autoflush that filehandle. You can use select()
and the C<$|> variable to control autoflushing (see L<perlvar/$E<verbar>>
-and L<perlfunc/select>, or L<perlfaq5>, ``How do I flush/unbuffer an
-output filehandle? Why must I do this?''):
+and L<perlfunc/select>, or L<perlfaq5>, "How do I flush/unbuffer an
+output filehandle? Why must I do this?"):
$oldh = select(DEV);
$| = 1;
generates a signal which is sent to your terminal's currently
foregrounded process group, which you then trap in your process.
Signals are documented in L<perlipc/"Signals"> and the
-section on ``Signals'' in the Camel.
+section on "Signals" in the Camel.
-You can set the values of the %SIG hash to be the functions you want
+You can set the values of the %SIG hash to be the functions you want
to handle the signal. After perl catches the signal, it looks in %SIG
for a key with the same name as the signal, then calls the subroutine
value for that key.
# as an anonymous subroutine
-
+
$SIG{INT} = sub { syswrite(STDERR, "ouch\n", 5 ) };
-
+
# or a reference to a function
-
+
$SIG{INT} = \&ouch;
-
+
# or the name of the function as a string
-
- $SIG{INT} = "ouch";
+
+ $SIG{INT} = "ouch";
Perl versions before 5.8 had in its C source code signal handlers which
would catch the signal and possibly run a Perl function that you had set
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"> or the section on ``Signals'' in
+flock() in L<perlipc/"Signals"> or the section on "Signals" in
the Camel Book.
If exception handling is all you're interested in, try the
use IPC::Open3;
use Symbol qw(gensym);
use IO::File;
- local *CATCHOUT = IO::File->new_tempfile;
- local *CATCHERR = IO::File->new_tempfile;
+ local *CATCHOUT = IO::File->new_tmpfile;
+ local *CATCHERR = IO::File->new_tmpfile;
my $pid = open3(gensym, ">&CATCHOUT", ">&CATCHERR", "cmd");
waitpid($pid, 0);
seek $_, 0, 0 for \*CATCHOUT, \*CATCHERR;
use IPC::Open3;
use Symbol qw(gensym);
use IO::File;
- local *CATCHERR = IO::File->new_tempfile;
+ local *CATCHERR = IO::File->new_tmpfile;
my $pid = open3(gensym, \*CATCHOUT, ">&CATCHERR", "cmd");
while( <CATCHOUT> ) {}
waitpid($pid, 0);
the current process group of your controlling terminal as follows:
use POSIX qw/getpgrp tcgetpgrp/;
- open(TTY, "/dev/tty") or die $!;
- $tpgrp = tcgetpgrp(fileno(*TTY));
- $pgrp = getpgrp();
- if ($tpgrp == $pgrp) {
- print "foreground\n";
+
+ # Some POSIX systems, such as Linux, can be
+ # without a /dev/tty at boot time.
+ if (!open(TTY, "/dev/tty")) {
+ print "no tty\n";
} else {
- print "background\n";
+ $tpgrp = tcgetpgrp(fileno(*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 in L<perlipc/"Signals"> and the section on
-``Signals'' in the Camel. You may instead use the more flexible
+"Signals" in the Camel. You may instead use the more flexible
Sys::AlarmCall module available from CPAN.
The alarm() function is not implemented on all versions of Windows.
you need to figure out the problem.
#!/usr/bin/perl -w
-
+
BEGIN {
$SIG{__WARN__} = sub{ print STDERR "Perl: ", @_; };
$SIG{__DIE__} = sub{ print STDERR "Perl: ", @_; exit 1};
}
-
+
$a = 1 + undef;
$x / 0;
__END__
get a new F<perl> binary with your extension linked in.
See L<ExtUtils::MakeMaker> for more details on building extensions.
-See also the next question, ``What's the difference between require
-and use?''.
+See also the next question, "What's the difference between require
+and use?".
=head2 What's the difference between require and use?
constants. Sometimes it is built using h2ph when Perl is installed,
but other times it is not. Modern programs C<use Socket;> instead.
+=head1 REVISION
+
+Revision: $Revision: 3606 $
+
+Date: $Date: 2006-03-06 12:05:47 +0100 (lun, 06 mar 2006) $
+
+See L<perlfaq> for source control details and availability.
+
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-2005 Tom Christiansen, Nathan Torkington, and
+Copyright (c) 1997-2006 Tom Christiansen, Nathan Torkington, and
other authors as noted. All rights reserved.
This documentation is free; you can redistribute it and/or modify it
projects / p5sagit/p5-mst-13.2.git / blobdiff