=head1 NAME
-perlfaq5 - Files and Formats ($Revision: 1.20 $, $Date: 1997/03/19 17:24:51 $)
+perlfaq5 - Files and Formats ($Revision: 1.22 $, $Date: 1997/04/24 22:44:02 $)
=head1 DESCRIPTION
rename($new, $old) or die "can't rename $new to $old: $!";
Perl can do this sort of thing for you automatically with the C<-i>
-command line switch or the closely-related C<$^I> variable (see
+command-line switch or the closely-related C<$^I> variable (see
L<perlrun> for more details). Note that
C<-i> may require a suffix on some non-Unix systems; see the
platform-specific documentation that came with your port.
may use that module directly if you'd like (see L<IO::Handle>), or
one of its more specific derived classes.
+Once you have IO::File or FileHandle objects, you can pass them
+between subroutines or store them in hashes as you would any other
+scalar values:
+
+ use FileHandle;
+
+ # Storing filehandles in a hash and array
+ foreach $filename (@names) {
+ my $fh = new FileHandle($filename) or die;
+ $file{$filename} = $fh;
+ push(@files, $fh);
+ }
+
+ # Using the filehandles in the array
+ foreach $file (@files) {
+ print $file "Testing\n";
+ }
+
+ # You have to do the { } ugliness when you're specifying the
+ # filehandle by anything other than a simple scalar variable.
+ print { $files[2] } "Testing\n";
+
+ # Passing filehandles to subroutines
+ sub debug {
+ my $filehandle = shift;
+ printf $filehandle "DEBUG: ", @_;
+ }
+
+ debug($fh, "Testing\n");
+
=head2 How can I set up a footer format to be used with write()?
There's no builtin way to do this, but L<perlform> has a couple of
because you have to put the comma in and then recalculate your
position.
+Alternatively, this commifies all numbers in a line regardless of
+whether they have decimal portions, are preceded by + or -, or
+whatever:
+
+ # from Andrew Johnson <ajohnson@gpu.srv.ualberta.ca>
+ sub commify {
+ my $input = shift;
+ $input = reverse $input;
+ $input =~ s<(\d\d\d)(?=\d)(?!\d*\.)><$1,>g;
+ return reverse $input;
+ }
+
=head2 How can I translate tildes (~) in a filename?
Use the E<lt>E<gt> (glob()) operator, documented in L<perlfunc>. This
except that lamentably, file creation (and deletion) is not atomic
over NFS, so this won't work (at least, not every time) over the net.
-Various schemes involving link() have been suggested, but these tend
-to involve busy-wait, which is also subdesirable.
+Various schemes involving involving link() have been suggested, but
+these tend to involve busy-wait, which is also subdesirable.
-=head2 I still don't get locking. I just want to increment the number
-in the file. How can I do this?
+=head2 I still don't get locking. I just want to increment the number in the file. How can I do this?
-Didn't anyone ever tell you web page hit counters were useless?
+Didn't anyone ever tell you web-page hit counters were useless?
Anyway, this is what to do:
# DO NOT UNLOCK THIS UNTIL YOU CLOSE
close FH or die "can't close numfile: $!";
-Here's a much better web page hit counter:
+Here's a much better web-page hit counter:
$hits = int( (time() - 850_000_000) / rand(1_000) );
Locking and error checking are left as an exercise for the reader.
Don't forget them, or you'll be quite sorry.
-Don't forget to set binmode() under MS-DOS-like platforms when operating
+Don't forget to set binmode() under DOS-like platforms when operating
on files that have anything other than straight text in them. See the
docs on open() and on binmode() for more details.
=head2 How do I get a file's timestamp in perl?
If you want to retrieve the time at which the file was last read,
-written, or had its metadata (owner, etc) changed, you use the B<-M>,
+written, or had its meta-data (owner, etc) changed, you use the B<-M>,
B<-A>, or B<-C> filetest operations as documented in L<perlfunc>. These
retrieve the age of the file (measured against the start-time of your
program) in days as a floating point number. To retrieve the "raw"
printf "\nYou said %s, char number %03d\n",
$key, ord $key;
-For MS-DOS systems, Dan Carson <dbc@tc.fluke.COM> reports the following:
+For DOS systems, Dan Carson <dbc@tc.fluke.COM> reports the following:
To put the PC in "raw" mode, use ioctl with some magic numbers gleaned
from msdos.c (Perl source file) and Ralf Brown's interrupt list (comes
$rc = syscall(&SYS_close, $fd + 0); # must force numeric
die "can't sysclose $fd: $!" unless $rc == -1;
-=head2 Why can't I use "C:\temp\foo" in MS-DOS paths? What doesn't `C:\temp\foo.exe` work?
+=head2 Why can't I use "C:\temp\foo" in DOS paths? What doesn't `C:\temp\foo.exe` work?
Whoops! You just put a tab and a formfeed into that filename!
Remember that within double quoted strings ("like\this"), the
backslash is an escape character. The full list of these is in
L<perlop/Quote and Quote-like Operators>. Unsurprisingly, you don't
have a file called "c:(tab)emp(formfeed)oo" or
-"c:(tab)emp(formfeed)oo.exe" on your MS-DOS filesystem.
+"c:(tab)emp(formfeed)oo.exe" on your DOS filesystem.
Either single-quote your strings, or (preferably) use forward slashes.
-Since all MS-DOS and Windows versions since something like MS-DOS 2.0 or so
+Since all DOS and Windows versions since something like MS-DOS 2.0 or so
have treated C</> and C<\> the same in a path, you might as well use the
one that doesn't clash with Perl -- or the POSIX shell, ANSI C and C++,
awk, Tcl, Java, or Python, just to mention a few.
=head2 Why doesn't glob("*.*") get all the files?
Because even on non-Unix ports, Perl's glob function follows standard
-Unix globbing semantics. You'll need C<glob("*")> to get all (nonhidden)
+Unix globbing semantics. You'll need C<glob("*")> to get all (non-hidden)
files.
=head2 Why does Perl let me delete read-only files? Why does C<-i> clobber protected files? Isn't this a bug in Perl?
Copyright (c) 1997 Tom Christiansen and Nathan Torkington.
All rights reserved. See L<perlfaq> for distribution information.
+
projects / p5sagit/p5-mst-13.2.git / blobdiff