cgi code line message

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

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Re: cgi code line message by Zaxo (Archbishop) on Jun 06, 2005 at 07:29 UTC
If you call warn or die without an explicit newline at the end of the message, you'll get file and line number in the text to STDERR. If you want your own error message function, you can pass it `__FILE__` and `__LINE__` so that its message gets to refer to the caller's location. Another way to do that is with the caller builtin. After Compline, Zaxo	[reply]
Re: cgi code line message by davido (Cardinal) on Jun 06, 2005 at 07:28 UTC
Here is a solution that involves a minimal edit to your existing code: `open( FILE, "$file" ) \|\| error_message( "File can not be opened: Line __LINE__.\n" );` [download] But when debugging CGI scripts, CGI::Carp can be much more useful, and would enable you to use die while dumping fatal error messages to the browser. Update: Dumb mistake here: `__LINE__` doesn't interpolate (nor should it). See my followup: Re^3: cgi code line message. Apologies! Dave	[reply] [d/l] [select]
Re^2: cgi code line message by Murcia (Monk) on Jun 06, 2005 at 07:54 UTC
sorry; but I tried your code and it did not work ... error_message( "File can not be opened: Line ". __LINE__. "\n" ); to be correct ... thanks a lot!	[reply]
Re^3: cgi code line message by davido (Cardinal) on Jun 06, 2005 at 08:28 UTC
My dumb mistake. Forgot that __LINE__ doesn't (and shouldn't) interpolate. Here ya go... `error_message( "File cannot be opened: Line " . __LINE__ . "\n" );` [download] Looks like you already figured it out though. Hope you find it helpful! Dave	[reply] [d/l]
Re: cgi code line message by brian_d_foy (Abbot) on Jun 06, 2005 at 08:41 UTC
In the error_message() routine, use the caller() function to figure out who called you from where. See the perlfunc entry for examples. -- brian d foy <brian@stonehenge.com>	[reply]
Re: cgi code line message by rupesh (Hermit) on Jun 06, 2005 at 10:35 UTC
Just an exerpt from of $! perldoc perlvar. $! If used numerically, yields the current value of the C "errno" variable, or in other words, if a system or library call fails, it sets this variable. This means that the value of $! is meaningful only immediately after a failure: `if (open(FH, $filename)) { # Here $! is meaningless. ... } else { # ONLY here is $! meaningful. ... # Already here $! might be meaningless. } # Since here we might have either success or failure, # here $! is meaningless.` [download] In the above meaningless stands for anything: zero, non-zero, "undef". A successful system or library call does not set the variable to zero. If used an a string, yields the corresponding system error string. You can assign a number to $! to set errno if, for instance, you want "$!" to return the string for error n, or you want to set the exit value for the die() operator. (Mnemonic: What just went bang?) Cheers, Rupesh.	[reply] [d/l]
Re: cgi code line message by jpeg (Chaplain) on Jun 06, 2005 at 07:57 UTC
Besides __LINE__, there's the special variable $. from perldoc perlvar: $. Current line number for the last filehandle accessed. Each filehandle in Perl counts the number of lines that have been read from it. (Depending on the value of $/, Perl's idea of what constitutes a line may not match yours.) </quote> Update: nevermind me, I'm an idiot. $. won't help in this case. /me wanders off... -- jpg	[reply]