Question

I am having some trouble trying to print from a file. Any ideas? Thanks

open(STDOUT,">/home/int420_101a05/shttpd/htdocs/receipt.html"); 
#Results of a sub-routine
&printReceipt; 
close(STDOUT);

open(INF,"/home/int420_101a05/shttpd/htdocs/receipt.html"); $emailBody = <INF>; 
close(INF); 
print $emailBody;

ERRORS: Filehandle STDOUT reopened as INF only for input at ./test.c line 6. 
print() on closed filehandle STDOUT at ./test.c line 9.

Answer 1

1. This discussion addresses the technical reason for the message. Relevant info from the thread is this:

   From open(2) manpage:

   When the call is successful, the file descriptor returned will be
   the lowest file descriptor not currently open for the process.

   But STDOUT still refers to the
   filehandle #1. This warning could be
   useful. Although one can argue that
   further uses of STDOUT as an output
   filehandle will trigger a warning as
   well…

   So, to summarize, you closed STDOUT (file descriptor 1) and your file will be open as FD#1. That’s due to open()'s properties.

2. As other have noted, the real reason you’re having this problem is that you should not use STDOUT for printing to a file unless there’s some special case where it’s required.

   Instead, open a file for writing using a new file handle:

   open(OUTFILE,">/home/int420_101a05/shttpd/htdocs/receipt.html")
      || die "Could not open: $!"; 
   print OUTFILE "data";
   close(OUTFILE);
   

3. To print to filehandle from subroutine, just pass the file handle as a parameter.

   The best way of doing so is to create an IO::File object and pass that object around

   my $filehandle = IO::File->new(">$filename") || die "error: $!";
   mySub($filehandle);
   
   sub mySub {
    my $fh = shift;
    print $fh "stuff" || die "could not print $!";    
   }
   

   You can also set a particular filehandle as a default filehandle to have print print to that by default using select but that is a LOT more fragile and should be avoidded in favor of IO::File solution.