=head1 NAME
-perlfaq8 - System Interaction ($Revision: 1.14 $, $Date: 2002/11/10 17:35:47 $)
+perlfaq8 - System Interaction ($Revision: 1.16 $, $Date: 2003/01/03 20:03:57 $)
=head1 DESCRIPTION
Controlling input buffering is a remarkably system-dependent matter.
On many systems, you can just use the B<stty> command as shown in
L<perlfunc/getc>, but as you see, that's already getting you into
-portability snags.
+portability snags.
open(TTY, "+</dev/tty") or die "no tty: $!";
system "stty cbreak </dev/tty >/dev/tty 2>&1";
=head2 How do I get the screen size?
-If you have Term::ReadKey module installed from CPAN,
+If you have Term::ReadKey module installed from CPAN,
you can use it to fetch the width and height in characters
and in pixels:
use Term::ReadKey;
($wchar, $hchar, $wpixels, $hpixels) = GetTerminalSize();
-This is more portable than the raw C<ioctl>, but not as
+This is more portable than the raw C<ioctl>, but not as
illustrative:
require 'sys/ioctl.ph';
If you expect characters to get to your device when you print() them,
you'll want to autoflush that filehandle. You can use select()
-and the C<$|> variable to control autoflushing (see L<perlvar/$|>
+and the C<$|> 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?''):
You have to be prepared to "reap" the child process when it finishes.
$SIG{CHLD} = sub { wait };
-
+
$SIG{CHLD} = 'IGNORE';
-
-You can also use a double fork. You immediately wait() for your
-first child, and the init daemon will wait() for your grandchild once
+
+You can also use a double fork. You immediately wait() for your
+first child, and the init daemon will wait() for your grandchild once
it exits.
unless ($pid = fork) {
properly, the getpw*() functions described in L<perlfunc> should in
theory provide (read-only) access to entries in 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(8)> for more details).
+varies from system to system--see L<passwd> for specifics) and use
+pwd_mkdb(8) to install it (see L<pwd_mkdb> for more details).
=head2 How do I set the time and date?
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).
+thread ends (see L<perlmod> manpage for more details).
For example, you can use this to make sure your filter program
managed to finish its output without filling up the disk:
END {
close(STDOUT) || die "stdout close failed: $!";
- }
+ }
The END block isn't called when untrapped signals kill the program,
though, so if you use END blocks you should also use
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.
+CPAN as well---someone may already have written a module to do it. On
+Windows, try Win32::API. On Macs, try Mac::Carbon. If no module
+has an interface to the C function, you can inline a bit of C in your
+Perl source with Inline::C.
=head2 Where do I get the include files to do ioctl() or syscall()?
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>). See
-L<perlipc/"Bidirectional Communication with Another Process"> and
+though (see L<IPC::Open2>). See
+L<perlipc/"Bidirectional Communication with Another Process"> and
L<perlipc/"Bidirectional Communication with Yourself">
You may also use the IPC::Open3 module (part of the standard perl
way to write maintainable code. Perl has several operators for
running external commands. Backticks are one; they collect the output
from the command for use in your program. The C<system> function is
-another; it doesn't do this.
+another; it doesn't do this.
Writing backticks in your program sends a clear message to the readers
of your code that you wanted to collect the output of the command.
process are not reflected in its parent--only in any 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.
+comp.unix.questions FAQ for details.
=back
=item *
-Open /dev/tty and use the TIOCNOTTY ioctl on it. See L<tty(4)>
+Open /dev/tty and use the TIOCNOTTY ioctl on it. See L<tty>
for details. Or better yet, you can just use the POSIX::setsid()
function, so you don't have to worry about process groups.
passes the signal on to the subprocess. Or you can check for it:
$rc = system($cmd);
- if ($rc & 127) { die "signal death" }
+ if ($rc & 127) { die "signal death" }
=head2 How do I open a file without blocking?
=head2 How do I install a module from CPAN?
The easiest way is to have a module also named CPAN do it for you.
-This module comes with perl version 5.004 and later.
+This module comes with perl version 5.004 and later.
$ perl -MCPAN -e shell
cpan shell -- CPAN exploration and modules installation (v1.59_54)
ReadLine support enabled
- cpan> install Some::Module
+ cpan> install Some::Module
-To manually install the CPAN module, or any well-behaved CPAN module
+To manually install the CPAN module, or any well-behaved CPAN module
for that matter, follow these steps:
=over 4
=head1 AUTHOR AND COPYRIGHT
-Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington.
+Copyright (c) 1997-2003 Tom Christiansen and Nathan Torkington.
All rights reserved.
This documentation is free; you can redistribute it and/or modify it
projects / p5sagit/p5-mst-13.2.git / blobdiff