Add in perldelta changes about unpack A and trailing whitespace, trie

[p5sagit/p5-mst-13.2.git] / pod / perlfaq5.pod

diff --git a/pod/perlfaq5.pod b/pod/perlfaq5.pod
index be10390..ab0ba26 100644 (file)
--- a/pod/perlfaq5.pod
+++ b/pod/perlfaq5.pod
@@ -1,6 +1,6 @@
 =head1 NAME
 
-perlfaq5 - Files and Formats ($Revision: 1.30 $, $Date: 2003/11/23 08:07:46 $)
+perlfaq5 - Files and Formats ($Revision: 1.35 $, $Date: 2005/01/21 12:26:11 $)
 
 =head1 DESCRIPTION
 
@@ -106,9 +106,31 @@ This block modifies all the C<.c> files in the current directory,
 leaving a backup of the original data from each file in a new
 C<.c.orig> file.
 
+=head2 How can I copy a file?
+
+(contributed by brian d foy)
+
+Use the File::Copy module. It comes with Perl and can do a
+true copy across file systems, and it does its magic in
+a portable fashion.
+
+       use File::Copy;
+
+       copy( $original, $new_copy ) or die "Copy failed: $!";
+
+If you can't use File::Copy, you'll have to do the work yourself:
+open the original file, open the destination file, then print
+to the destination file as you read the original.
+
 =head2 How do I make a temporary file name?
 
-Use the File::Temp module, see L<File::Temp> for more information.
+If you don't need to know the name of the file, you can use C<open()>
+with C<undef> in place of the file name.  The C<open()> function
+creates an anonymous temporary file.
+
+       open my $tmp, '+>', undef or die $!;
+       
+Otherwise, you can use the File::Temp module.
 
   use File::Temp qw/ tempfile tempdir /;
 
@@ -141,6 +163,7 @@ temporary files in one process, use a counter:
            my $count = 0;
            until (defined(fileno(FH)) || $count++ > 100) {
                $base_name =~ s/-(\d+)$/"-" . (1 + $1)/e;
+               # O_EXCL is required for security reasons.
                sysopen(FH, $base_name, O_WRONLY|O_EXCL|O_CREAT);
            }
            if (defined(fileno(FH))
@@ -332,7 +355,7 @@ It is easier to see with comments:
 
    s/(
        ^[-+]?            # beginning of number.
-       \d{1,3}?          # first digits before first comma
+       \d+?              # first digits before first comma
        (?=               # followed by, (but not included in the match) :
           (?>(?:\d{3})+) # some positive multiple of three digits.
           (?!\d)         # an *exact* multiple, not x * 3 + 1 or whatever.
@@ -427,8 +450,8 @@ To open file for update, file must not exist:
 
 To open a file without blocking, creating if necessary:
 
-    sysopen(FH, "/tmp/somefile", O_WRONLY|O_NDELAY|O_CREAT)
-           or die "can't open /tmp/somefile: $!":
+    sysopen(FH, "/foo/somefile", O_WRONLY|O_NDELAY|O_CREAT)
+           or die "can't open /foo/somefile: $!":
 
 Be warned that neither creation nor deletion of files is guaranteed to
 be an atomic operation over NFS.  That is, two processes might both
@@ -683,9 +706,14 @@ of them.
 
 Error checking is, as usual, left as an exercise for the reader.
 
-Note that utime() currently doesn't work correctly with Win95/NT
-ports.  A bug has been reported.  Check it carefully before using
-utime() on those platforms.
+The perldoc for utime also has an example that has the same
+effect as touch(1) on files that I<already exist>.
+
+Certain file systems have a limited ability to store the times
+on a file at the expected level of precision.  For example, the
+FAT and HPFS filesystem are unable to create dates on files with
+a finer granularity than two seconds.  This is a limitation of
+the filesystems, not of utime().
 
 =head2 How do I print to more than one file at once?
 
@@ -924,7 +952,7 @@ There's also a File::Tail module from CPAN.
 If you check L<perlfunc/open>, you'll see that several of the ways
 to call open() should do the trick.  For example:
 
-    open(LOG, ">>/tmp/logfile");
+    open(LOG, ">>/foo/logfile");
     open(STDERR, ">&LOG");
 
 Or even with a literal numeric descriptor:
@@ -1041,8 +1069,8 @@ If your array contains lines, just print them:
 
 =head1 AUTHOR AND COPYRIGHT
 
-Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington.
-All rights reserved.
+Copyright (c) 1997-2005 Tom Christiansen, Nathan Torkington, and
+other authors as noted. All rights reserved.
 
 This documentation is free; you can redistribute it and/or modify it
 under the same terms as Perl itself.