| PerlFAQ Server 2005-06-09, 8:57 pm |
| This message is one of several periodic postings to comp.lang.perl.misc
intended to make it easier for perl programmers to find answers to
common questions. The core of this message represents an excerpt
from the documentation provided with Perl.
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9.1: What is the correct form of response from a CGI script?
(Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...)
The Common Gateway Interface (CGI) specifies a software interface
between a program ("CGI script") and a web server (HTTPD). It is not
specific to Perl, and has its own FAQs and tutorials, and usenet group,
comp.infosystems.www.authoring.cgi
The CGI specification is outlined in an informational RFC:
http://www.ietf.org/rfc/rfc3875
Other relevant documentation listed in:
http://www.perl.org/CGI_MetaFAQ.html
These Perl FAQs very selectively cover some CGI issues. However, Perl
programmers are strongly advised to use the CGI.pm module, to take care
of the details for them.
The similarity between CGI response headers (defined in the CGI
specification) and HTTP response headers (defined in the HTTP
specification, RFC2616) is intentional, but can sometimes be confusing.
The CGI specification defines two kinds of script: the "Parsed Header"
script, and the "Non Parsed Header" (NPH) script. Check your server
documentation to see what it supports. "Parsed Header" scripts are
simpler in various respects. The CGI specification allows any of the
usual newline representations in the CGI response (it's the server's job
to create an accurate HTTP response based on it). So "\n" written in
text mode is technically correct, and recommended. NPH scripts are more
tricky: they must put out a complete and accurate set of HTTP
transaction response headers; the HTTP specification calls for records
to be terminated with carriage-return and line-feed, i.e ASCII \015\012
written in binary mode.
Using CGI.pm gives excellent platform independence, including EBCDIC
systems. CGI.pm selects an appropriate newline representation
($CGI::CRLF) and sets binmode as appropriate.
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