cvs commit: perlfaq perlfaq5.pod

cvsuser     02/03/11 13:39:21

  Modified:    .        perlfaq5.pod
  Log:
  * added a new answer for 'How do I add commas...'.  the new
  answer is a regular expression rather than a loop or
  subroutine like the previous answer.
  
  * changed the answer for 'How can I open a file with a leading
  
  Revision  Changes    Path
  1.10      +36 -58    perlfaq/perlfaq5.pod
  
  Index: perlfaq5.pod
  ===================================================================
  RCS file: /cvs/public/perlfaq/perlfaq5.pod,v
  retrieving revision 1.9
  retrieving revision 1.10
  diff -u -w -r1.9 -r1.10
  --- perlfaq5.pod	11 Feb 2002 19:30:21 -0000	1.9
  +++ perlfaq5.pod	11 Mar 2002 21:39:21 -0000	1.10
  @@ -1,6 +1,6 @@
   =head1 NAME
   
  -perlfaq5 - Files and Formats ($Revision: 1.9 $, $Date: 2002/02/11 19:30:21 $)
  +perlfaq5 - Files and Formats ($Revision: 1.10 $, $Date: 2002/03/11 21:39:21 $)
   
   =head1 DESCRIPTION
   
  @@ -425,37 +425,23 @@
   
   =head2 How can I output my numbers with commas added?
   
  -This one will do it for you:
  +This one from Benjamin Goldberg will do it for you:
   
  -    sub commify {
  -        my $number = shift;
  -	1 while ($number =~ s/^([-+]?\d+)(\d{3})/$1,$2/);
  -	return $number;
  -    }
  -
  -    $n = 23659019423.2331;
  -    print "GOT: ", commify($n), "\n";
  -
  -    GOT: 23,659,019,423.2331
  -
  -You can't just:
  -
  -    s/^([-+]?\d+)(\d{3})/$1,$2/g;
  -
  -because you have to put the comma in and then recalculate your
  -position.
  +   s/(^[-+]?\d+?(?=(?>(?:\d{3})+)(?!\d))|\G\d{3}(?=\d))/$1,/g;
   
  -Alternatively, this code commifies all numbers in a line regardless of
  -whether they have decimal portions, are preceded by + or -, or
  -whatever:
  +or written verbosely:
   
  -    # from Andrew Johnson <[email protected]>
  -    sub commify {
  -       my $input = shift;
  -        $input = reverse $input;
  -        $input =~ s<(\d\d\d)(?=\d)(?!\d*\.)><$1,>g;
  -        return scalar reverse $input;
  -    }
  +   s/(
  +       ^[-+]?            # beginning of number.
  +       \d{1,3}?          # 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.
  +       )
  +      |                  # or:
  +       \G\d{3}           # after the last group, get three digits
  +       (?=\d)            # but they have to have more digits after them.
  +   )/$1,/xg;
   
   =head2 How can I translate tildes (~) in a filename?
   
  @@ -576,35 +562,24 @@
   
   Normally perl ignores trailing blanks in filenames, and interprets
   certain leading characters (or a trailing "|") to mean something
  -special.  To avoid this, you might want to use a routine like the one below.
  -It turns incomplete pathnames into explicit relative ones, and tacks a
  -trailing null byte on the name to make perl leave it alone:
  -
  -    sub safe_filename {
  -	local $_  = shift;
  -        s#^([^./])#./$1#;
  -        $_ .= "\0";
  -	return $_;
  -    }
  +special. 
   
  -    $badpath = "<<<something really wicked   ";
  -    $fn = safe_filename($badpath");
  -    open(FH, "> $fn") or "couldn't open $badpath: $!";
  +The three argument form of open() lets you specify the mode
  +separately from the filename.  The open() function treats
  +special mode characters and whitespace in the filename as 
  +literals
  +
  +	open FILE, "<", "  file  ";  # filename is "   file   "
  +	open FILE, ">", ">file";     # filename is ">file"
   
  -This assumes that you are using POSIX (portable operating systems
  -interface) paths.  If you are on a closed, non-portable, proprietary
  -system, you may have to adjust the C<"./"> above.
   
  -It would be a lot clearer to use sysopen(), though:
  +It may be a lot clearer to use sysopen(), though:
   
       use Fcntl;
       $badpath = "<<<something really wicked   ";
       sysopen (FH, $badpath, O_WRONLY | O_CREAT | O_TRUNC)
   	or die "can't open $badpath: $!";
   
  -For more information, see also the new L<perlopentut> if you have it
  -(new for 5.6).
  -
   =head2 How can I reliably rename a file?
   
   If your operating system supports a proper mv(1) utility or its functional
  @@ -763,14 +738,17 @@
   
   =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 meta-data (owner, etc) changed, you use the B<-M>,
  -B<-A>, or B<-C> file test 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"
  -time in seconds since the epoch, you would call the stat function,
  -then use localtime(), gmtime(), or POSIX::strftime() to convert this
  -into human-readable form.
  +If you want to retrieve the time at which the file was last
  +read, written, or had its meta-data (owner, etc) changed,
  +you use the B<-M>, B<-A>, or B<-C> file test 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. Some platforms may not have
  +all of these times.  See L<perlport> for details. To
  +retrieve the "raw" time in seconds since the epoch, you
  +would call the stat function, then use localtime(),
  +gmtime(), or POSIX::strftime() to convert this into
  +human-readable form.
   
   Here's an example: