FAQ: What is the correct form of response from a CGI script?

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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
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9.1: What is the correct form of response from a CGI script?

    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,

    The original CGI specification is at: http://hoohoo.ncsa.uiuc.edu/cgi /

    Current best-practice RFC draft at: http://CGI-Spec.Golux.Com /

    Other relevant documentation listed in:

    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 52
    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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