Checking a header is printed already?

ultranerds has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Checking a header is printed already? by Bloodnok (Vicar) on Oct 06, 2009 at 12:09 UTC
As AM suggests, re-factoring would not be a bad idea. Maybe emulate, but definitely not directly use, the inner workings of CGI by implementing a wrapper sub of your own that conditionally calls `CGI::header()` i.e. knows whether or not it's already printed a header. A user level that continues to overstate my experience :-))	[reply] [d/l]
Re: Checking a header is printed already? by almut (Canon) on Oct 06, 2009 at 11:42 UTC
You could use a global variable (accessible from every place where you're potentially outputting the header) to keep track of whether it's already been printed: `unless ($header_printed) { $header_printed = print $IN->header; }` [download]	[reply] [d/l]
Re^2: Checking a header is printed already? by Anonymous Monk on Oct 06, 2009 at 11:52 UTC
Oh , CGI, `#### Method: header # Return a Content-Type: style header # #### 'header' => <<'END_OF_FUNC', sub header { my($self,@p) = self_or_default(@_); my(@header); return "" if $self->{'.header_printed'}++ and $HEADERS_ONCE;` [download] `# Change this to 1 to suppress redundant HTTP headers $HEADERS_ONCE = 0;` [download] `$HEADERS_ONCE++, next if /^[:-]unique_headers$/;` [download] `use CGI qw( -unique_headers );` [download]	[reply] [d/l] [select]
Re^3: Checking a header is printed already? by Bloodnok (Vicar) on Oct 06, 2009 at 11:56 UTC
Hmmm, utilising & referencing a modules' implementation details ... definitely a bad idea!! A user level that continues to overstate my experience :-))	[reply]
Re^4: Checking a header is printed already? by Anonymous Monk on Oct 06, 2009 at 12:28 UTC
Re^5: Checking a header is printed already? by Bloodnok (Vicar) on Oct 06, 2009 at 16:35 UTC
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Re^3: Checking a header is printed already? by ultranerds (Hermit) on Oct 06, 2009 at 12:11 UTC
Hi, Thanks for the replies guys. From looking at that header() bit in CGI.pm, it looks like CGI.pm already does the checking for me? (maybe that would explain why I'm not seing "Content-Type: text/html" printed several times, where the header is called :) Thanks! Andy	[reply]
Re^4: Checking a header is printed already? by Anonymous Monk on Oct 06, 2009 at 12:25 UTC
Re^5: Checking a header is printed already? by ultranerds (Hermit) on Oct 06, 2009 at 13:23 UTC
Re: Checking a header is printed already? by Anonymous Monk on Oct 06, 2009 at 11:34 UTC
If you need to know this, it is time to refactor your program, but you can use tell `perl -le"print tell(STDOUT) for 1 .. 3" 0 3 6` [download]	[reply] [d/l]
Re^2: Checking a header is printed already? by Bloodnok (Vicar) on Oct 06, 2009 at 12:02 UTC
...so long as the stream is buffered - from tell: ...on a file handle that has been manipulated by sysread(), syswrite() or sysseek(). Those functions ignore the buffering, while tell() does not. A user level that continues to overstate my experience :-))	[reply]