From 197aec242db45fbf1d7853a1ae22a108cc09d23c Mon Sep 17 00:00:00 2001 From: Rafael Garcia-Suarez Date: Wed, 8 Jan 2003 20:48:19 +0000 Subject: PerlFAQ sync. p4raw-id: //depot/perl@18459 --- pod/perlfaq8.pod | 51 +++++++++++++++++++++++++++------------------------ 1 file changed, 27 insertions(+), 24 deletions(-) (limited to 'pod/perlfaq8.pod') diff --git a/pod/perlfaq8.pod b/pod/perlfaq8.pod index e00d007912..31af4bd7df 100644 --- a/pod/perlfaq8.pod +++ b/pod/perlfaq8.pod @@ -1,6 +1,6 @@ =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 $) =head1 DESCRIPTION @@ -77,7 +77,7 @@ Or like this: Controlling input buffering is a remarkably system-dependent matter. On many systems, you can just use the B command as shown in L, but as you see, that's already getting you into -portability snags. +portability snags. open(TTY, "+/dev/tty 2>&1"; @@ -188,14 +188,14 @@ positions, etc, you might wish to use Term::Cap module: =head2 How do I get the screen size? -If you have Term::ReadKey module installed from CPAN, +If you have Term::ReadKey module installed from CPAN, you can use it to fetch the width and height in characters and in pixels: use Term::ReadKey; ($wchar, $hchar, $wpixels, $hpixels) = GetTerminalSize(); -This is more portable than the raw C, but not as +This is more portable than the raw C, but not as illustrative: require 'sys/ioctl.ph'; @@ -275,7 +275,7 @@ next. If you expect characters to get to your device when you print() them, you'll want to autoflush that filehandle. You can use select() -and the C<$|> variable to control autoflushing (see L +and the C<$|> variable to control autoflushing (see L> and L, or L, ``How do I flush/unbuffer an output filehandle? Why must I do this?''): @@ -383,11 +383,11 @@ not an issue with C. 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) { @@ -445,8 +445,8 @@ If perl was installed correctly and your shadow library was written properly, the getpw*() functions described in L 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 for specifics) and use -pwd_mkdb(8) to install it (see L for more details). +varies from system to system--see L for specifics) and use +pwd_mkdb(8) to install it (see L for more details). =head2 How do I set the time and date? @@ -511,14 +511,14 @@ something like this: 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 manpage for more details). +thread ends (see L 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 @@ -556,7 +556,10 @@ syscall(), you can use the syscall function (documented in L). 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()? @@ -594,8 +597,8 @@ scripts inherently insecure. Perl gives you a number of options 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). See -L and +though (see L). See +L and L You may also use the IPC::Open3 module (part of the standard perl @@ -783,7 +786,7 @@ Strictly speaking, nothing. Stylistically speaking, it's not a good 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 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. @@ -944,7 +947,7 @@ different process from the shell it was started from. Changes to a 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 @@ -965,7 +968,7 @@ module for other solutions. =item * -Open /dev/tty and use the TIOCNOTTY ioctl on it. See L +Open /dev/tty and use the TIOCNOTTY ioctl on it. See L for details. Or better yet, you can just use the POSIX::setsid() function, so you don't have to worry about process groups. @@ -1044,7 +1047,7 @@ sample code) and then have a signal handler for the INT signal that 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? @@ -1060,16 +1063,16 @@ sysopen(): =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 @@ -1176,7 +1179,7 @@ but other times it is not. Modern programs C instead. =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 -- cgit v1.2.1