What causes 'premature end of script headers'?

[markjugg]

What are possible causes of the 'premature end of script headers' message in a web server's error log after the failed execution of a Perl CGI script?

Originally posted as a Categorized Question.

[Aristotle]

Not having output a header when you should have. Whether that is because the script didn't compile or was aborted before it reached the code to output the header, the result is the same. Consult your server's error log to find out the actual error message.

[markjugg]

Here are some ideas:
• Something printed to STDERR
• The "Content-Type" header is invalid or missing.
• You are using SuExec and it's causing problems.

For further ideas, you can:

• read the FAQ included in the perl documentation: perldoc -q 500 or perldoc perlfaq8
• Try meryln's tips
• Check the related Apache documentation
• check that the line break style is correct
• Make sure the shebang line is correct.
• Try CGI::Carp qw(fatalsToBrowser); or CGI::Debug

Mark

[naikonta]

Something printed to STDERR

What does STDERR have anything to do with PESH?

[jhourcle]

Something printing to STDOUT before the headers have been sent, and a blank line has also been sent to mark the end of the headers, or an incorrectly formatted header was sent. You can debug these issues by printing immediately print "Content-type: text/plain\n\n"; and looking at the output that is generated.

If you're using CGIwrap, you can use the debugging mode to see what content was generated, including the headers. suEXEC can also provide some debugging help.

[solegaonkar]

I faced this problem because of DOS end of line characters in the file. Fixed with dos2unix

[LesleyB]

You might have a bug in your code.

use CGI::Carp qw(fatalsToBrowser);

will throw errors up to the browser.

You can also run cgi scripts from the command line to check they actually run.

[gvs_jagan]

You could encounter the 'premature end of script headers'

1) In case you were trying to accept values from a html page thru textfields

per se

print p("enter your name" , textfield("nam","");

missing out on one of the coats could cause it. For instance

print p("enter your name", textfield("nam , ""); #the end coat near nam is missing, this could cause

2) Also if you forget paranthesis near the html headers . In the below mentioned case missing out the paranthesis near the end_html could cause you the error

print header, start_html() ;
end_html();# leaving the paranthesis here

regards jagan