=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
=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.
+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:
=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?
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)?
+=head2 Why can't my script read from STDIN after I gave it EOF (^D on Unix, ^Z on MS-DOS)?
Because some stdio's set error and eof flags that need clearing. The
POSIX module defines clearerr() that you can use. That is the
=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 $handle;
+ exit;
=head2 How can I write expect in Perl?
See the F<eg/nih> script (part of the perl source distribution).
-=head2 How do I keep my own module/library directory?
-
-When you build modules, use the PREFIX option when generating
-Makefiles:
-
- perl Makefile.PL PREFIX=/u/mydir/perl
-
-then either set the PERL5LIB environment variable before you run
-scripts that use the modules/libraries (see L<perlrun>) or say
-
- use lib '/u/mydir/perl';
-
-See Perl's L<lib> for more information.
-
=head2 How do I find out if I'm running interactively or not?
Good question. Sometimes C<-t STDIN> and C<-t STDOUT> can give clues,
just need to replace step 3 (B<make>) with B<make perl> and you will
get a new F<perl> binary with your extension linked in.
-See L<ExtUtils::MakeMaker> for more details on building extensions.
+See L<ExtUtils::MakeMaker> for more details on building extensions
+and an answer to the question "How do I keep my own module/library
+directory?"
+
+=head2 How do I keep my own module/library directory?
+
+When you build modules, use the PREFIX option when generating
+Makefiles:
+
+ perl Makefile.PL PREFIX=/u/mydir/perl
+
+then either set the PERL5LIB environment variable before you run
+scripts that use the modules/libraries (see L<perlrun>) or say
+
+ use lib '/u/mydir/perl';
+
+See Perl's L<lib> for more information.
+
+=head2 How do I add the directory my program lives in to the module/library search path?
+
+ use FindBin;
+ use lib "$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
projects / p5sagit/p5-mst-13.2.git / blobdiff