which is definitely not what you want.
The other important thing to notice is that, just as in the shell,
-any white space before or after the filename is ignored. This is good,
+any whitespace before or after the filename is ignored. This is good,
because you wouldn't want these to do different things:
open INFO, "<datafile"
This is not a bug, but a feature. Because C<open> mimics the shell in
its style of using redirection arrows to specify how to open the file, it
-also does so with respect to extra white space around the filename itself
+also does so with respect to extra whitespace around the filename itself
as well. For accessing files with naughty names, see
L<"Dispelling the Dweomer">.
open(WTMP, "+< /usr/adm/wtmp")
|| die "can't open /usr/adm/wtmp: $!";
- open(SCREEN, "+> /tmp/lkscreen")
- || die "can't open /tmp/lkscreen: $!";
+ open(SCREEN, "+> lkscreen")
+ || die "can't open lkscreen: $!";
- open(LOGFILE, "+>> /tmp/applog"
- || die "can't open /tmp/applog: $!";
+ open(LOGFILE, "+>> /var/log/applog"
+ || die "can't open /var/log/applog: $!";
The first one won't create a new file, and the second one will always
clobber an old one. The third one will create a new file if necessary
The HANDLE argument is a filehandle just as with C<open>. The PATH is
a literal path, one that doesn't pay attention to any greater-thans or
-less-thans or pipes or minuses, nor ignore white space. If it's there,
+less-thans or pipes or minuses, nor ignore whitespace. If it's there,
it's part of the path. The FLAGS argument contains one or more values
derived from the Fcntl module that have been or'd together using the
bitwise "|" operator. The final argument, the MASK, is optional; if
Here's how to use C<sysopen> to emulate the simple C<open> calls we had
before. We'll omit the C<|| die $!> checks for clarity, but make sure
you always check the return values in real code. These aren't quite
-the same, since C<open> will trim leading and trailing white space,
+the same, since C<open> will trim leading and trailing whitespace,
but you'll get the idea.
To open a file for reading:
NULs within a valid filename. Most systems follow these conventions,
including all POSIX systems as well as proprietary Microsoft systems.
The only vaguely popular system that doesn't work this way is the
-proprietary Macintosh system, which uses a colon where the rest of us
+"Classic" Macintosh system, which uses a colon where the rest of us
use a slash. Maybe C<sysopen> isn't such a bad idea after all.
If you want to use C<< <ARGV> >> processing in a totally boring
open(STDOUT, "> output")
|| die "can't open output: $!";
-And then these can be read directly or passed on to subprocesses.
+And then these can be accessed directly or passed on to subprocesses.
This makes it look as though the program were initially invoked
with those redirections from the command line.
sub head {
my $lines = shift || 20;
- return unless $pid = open(STDOUT, "|-");
+ return if $pid = open(STDOUT, "|-"); # return if parent
die "cannot fork: $!" unless defined $pid;
while (<STDIN>) {
- print;
last if --$lines < 0;
+ print;
}
exit;
}
sockets, you can set them to be non-blocking using C<fcntl>:
use Fcntl;
- fcntl(Connection, F_SETFL, O_NONBLOCK)
+ my $old_flags = fcntl($handle, F_GETFL, 0)
+ or die "can't get flags: $!";
+ fcntl($handle, F_SETFL, $old_flags | O_NONBLOCK)
or die "can't set non blocking: $!";
Rather than losing yourself in a morass of twisting, turning C<ioctl>s,
=back
-For more detailed discussion about PerlIO see L<perlio>;
+For more detailed discussion about PerlIO see L<PerlIO>;
for more detailed discussion about Unicode and I/O see L<perluniintro>.
=head1 SEE ALSO
https://perl5.git.perl.org / perl5.git / blobdiff