NAME

Apache - Perl interface to the Apache server API

SYNOPSIS

   use Apache ();

DESCRIPTION

This module provides a Perl interface the Apache API. It is here mainly for mod_perl, but may be used for other Apache modules that wish to embed a Perl interpreter. We suggest that you also consult the description of the Apache C API at http://www.apache.org/docs/.

THE REQUEST OBJECT

The request object holds all the information that the server needs to service a request. Apache Perl*Handlers will be given a reference to the request object as parameter and may choose update or use it in various ways. Most of the methods described below obtain information from or updates the request object. The perl version of the request object will be blessed into the Apache package, it is really a request_rec* in disguise.

Apache->request([$r])

The Apache->request method will return a reference to the request object.

Perl*Handlers can obtain a reference to the request object when it is passed to them via @_. However, scripts that run under Apache::Registry, for example, need a way to access the request object. Apache::Registry will make a request object available to these scripts by passing an object reference to Apache->request($r). If handlers use modules such as CGI::Apache that need to access Apache->request, they too should do this (e.g. Apache::Status).

$r->as_string

Returns a string representation of the request object. Mainly useful for debugging.

$r->main

If the current request is a sub-request, this method returns a blessed reference to the main request structure. If the current request is the main request, then this method returns undef.

$r->prev

This method returns a blessed reference to the previous (internal) request structure or undef if there is no previous request.

$r->next

This method returns a blessed reference to the next (internal) request structure or undef if there is no next request.

$r->is_main

Returns true if the current request object is for the main request. (Should give the same result as !$r->main, but will be more efficient.)

$r->is_initial_req

Returns true if the current request is the first internal request, returns false if the request is a sub-request or internal redirect.

SUB REQUESTS

Apache provides a sub-request mechanism to lookup a uri or filename, performing all access checks, etc., without actually running the response phase of the given request. Notice, we have dropped the sub_req_ prefix here. The request_rec* returned by the lookup methods is blessed into the Apache::SubRequest class. This way, destroy_sub_request() is called automatically during Apache::SubRequest->DESTROY when the object goes out of scope. The Apache::SubRequest class inherits all the methods from the Apache class.

$r->lookup_uri($uri)

   my $subr = $r->lookup_uri($uri);
   my $filename = $subr->filename;

   unless(-e $filename) {
       warn "can't stat $filename!\n";
   }

$r->lookup_file($filename)

   my $subr = $r->lookup_file($filename);

$subr->run

   if($subr->run != OK) {
       $subr->log_error("something went wrong!");
   }

CLIENT REQUEST PARAMETERS

In this section we will take a look at various methods that can be used to retrieve the request parameters sent from the client. In the following examples, $r is a request object blessed into the Apache class, obtained by the first parameter passed to a handler subroutine or Apache->request

$r->method( [$meth] )

The $r->method method will return the request method. It will be a string such as "GET", "HEAD" or "POST". Passing an argument will set the method, mainly used for internal redirects.

$r->method_number( [$num] )

The $r->method_number method will return the request method number. The method numbers are defined by the M_GET, M_POST,... constants available from the Apache::Constants module. Passing an argument will set the method_number, mainly used for internal redirects and testing authorization restriction masks.

$r->bytes_sent

The number of bytes sent to the client, handy for logging, etc.

$r->the_request

The request line send by the client, handy for logging, etc.

$r->proxyreq

Returns true if the request is proxy http. Mainly used during the filename translation stage of the request, which may be handled by a PerlTransHandler.

$r->header_only

Returns true if the client is asking for headers only, e.g. if the request method was HEAD.

$r->protocol

The $r->protocol method will return a string identifying the protocol that the client speaks. Typical values will be "HTTP/1.0" or "HTTP/1.1".

$r->uri( [$uri] )

The $r->uri method will return the requested URI, optionally changing it with the first argument.

$r->filename( [$filename] )

The $r->filename method will return the result of the URI --> filename translation, optionally changing it with the first argument if you happen to be doing the translation.

$r->path_info( [$path_info] )

The $r->path_info method will return what is left in the path after the URI --> filename translation, optionally changing it with the first argument if you happen to be doing the translation.

$r->args

The $r->args method will return the contents of the URI query string. When called in a scalar context, the entire string is returned. When called in a list context, a list of parsed key => value pairs are returned, i.e. it can be used like this:

   $query = $r->args;
   %in    = $r->args;

$r->headers_in

The $r->headers_in method will return a %hash of client request headers. This can be used to initialize a perl hash, or one could use the $r->header_in() method (described below) to retrieve a specific header value directly.

$r->header_in( $header_name, [$value] )

Return the value of a client header. Can be used like this:

   $ct = $r->header_in("Content-type");
   $r->header_in($key, $val); #set the value of header '$key'

$r->content

The $r->content method will return the entity body read from the client, but only if the request content type is application/x-www-form-urlencoded. When called in a scalar context, the entire string is returned. When called in a list context, a list of parsed key => value pairs are returned. *NOTE*: you can only ask for this once, as the entire body is read from the client.

$r->read_client_block($buf, $bytes_to_read)

Read from the entity body sent by the client. Example of use:

   $r->read_client_block($buf, $r->header_in('Content-length'));

$r->read($buf, $bytes_to_read)

This method uses read_client_block() to read data from the client, looping until it gets all of $bytes_to_read or a timeout happens.

In addition, this method sets a timeout before reading with $r->hard_timeout

$r->get_remote_host

Lookup the client's DNS hostname. If the configuration directive HostNameLookups is set to off, this returns the dotted decimal representation of the client's IP address instead. Might return undef if the hostname is not known.

$r->get_remote_logname

Lookup the remote user's system name. Might return undef if the remote system is not running an RFC 1413 server or if the configuration directive IdentityCheck is not turned on.

More information about the client can be obtained from the Apache::Connection object, as described below.

$c = $r->connection

The $r->connection method will return a reference to the request connection object (blessed into the Apache::Connection package). This is really a conn_rec* in disguise. The following methods can be used on the connection object:

$c->remote_host

If the configuration directive HostNameLookups is set to on: then the first time $r->get_remote_host is called the server does a DNS lookup to get the remote client's host name. The result is cached in $c->remote_host then returned. If the server was unable to resolve the remote client's host name this will be set to "". Subsequent calls to $r->get_remote_host return this cached value.

If the configuration directive HostNameLookups is set to off: calls to $r->get_remote_host return a string that contains the dotted decimal representation of the remote client's IP address. However this string is not cached, and $c->remote_host is undefined. So, it's best to to call $r->get_remote_host instead of directly accessing this variable.

$c->remote_ip

The dotted decimal representation of the remote client's IP address. This is set by then server when the connection record is created so is always defined.

$c->local_addr

A packed SOCKADDR_IN in the same format as returned by "pack_sockaddr_in" in Socket, containing the port and address on the local host that the remote client is connected to. This is set by the server when the connection record is created so it is always defined.

$c->remote_addr

A packed SOCKADDR_IN in the same format as returned by "pack_sockaddr_in" in Socket, containing the port and address on the remote host that the server is connected to. This is set by the server when the connection record is created so it is always defined.

Among other things, this can be used, together with $c->local_addr, to perform RFC1413 ident lookups on the remote client even when the configuration directive IdentityCheck is turned off.

Can be used like:

   use Net::Ident qw (lookupFromInAddr);
   ...
   my $remoteuser = lookupFromInAddr ($c->local_addr,
                                      $c->remote_addr, 2);

Note that the lookupFromInAddr interface does not currently exist in the Net::Ident module, but the author is planning on adding it soon.

$c->remote_logname

If the configuration directive IdentityCheck is set to on: then the first time $r->get_remote_logname is called the server does an RFC 1413 (ident) lookup to get the remote user's system name. Generally for UNI* systems this is their login. The result is cached in $c->remote_logname then returned. Subsequent calls to $r->get_remote_host return the cached value.

If the configuration directive IdentityCheck is set to off: then $r->get_remote_logname does nothing and $c->remote_logname is always undefined.

$c->user

If an authentication check was successful, the authentication handler caches the user name here.

$c->auth_type

Returns the authentication scheme that successfully authenticate $c->user, if any.

$c->aborted

Returns true if the client stopped talking to us.

SERVER CONFIGURATION INFORMATION

The following methods are used to obtain information from server configuration and access control files.

$r->dir_config( $key )

Returns the value of a per-directory variable specified by the PerlSetVar directive.

   # <Location /foo/bar>
   # SetPerlVar  Key  Value
   # </Location>

   my $val = $r->dir_config('Key');

$r->requires

Returns an array reference of hash references, containing information related to the require directive. This is normally used for access control, see Apache::AuthzAge for an example.

$r->auth_type

Returns a reference to the current value of the per directory configuration directive AuthType. Normally this would be set to Basic to use the basic authentication scheme defined in RFC 1945, Hypertext Transfer Protocol -- HTTP/1.0. However, you could set to something else and implement your own authentication scheme.

$r->auth_name

Returns a reference to the current value of the per directory configuration directive AuthName. The AuthName directive creates protection realm within the server's document space. To quote RFC 1945 "These realms allow the protected resources on a server to be partitioned into a set of protection spaces, each with its own authentication scheme and/or authorization database." The client uses the root URL of the server to determine which authentication credentials to send with each HTTP request. These credentials are tagged with the name of the authentication realm that created them. Then during the authentication stage the server uses the current authentication realm, from $r->auth_name, to determine which set of credentials to authenticate.

$r->document_root

Returns a reference to the current value of the per server configuration directive DocumentRoot. To quote the Apache server documentation, "Unless matched by a directive like Alias, the server appends the path from the requested URL to the document root to make the path to the document." This same value is passed to CGI scripts in the DOCUMENT_ROOT environment variable.

$r->allow_options

The $r->allow_options method can be used for checking if it is OK to run a perl script. The Apache::Options module provides the constants to check against.

   if(!($r->allow_options & OPT_EXECCGI)) {
       $r->log_reason("Options ExecCGI is off in this directory", 
                      $filename);
   }

$s = $r->server

Return a reference to the server info object (blessed into the Apache::Server package). This is really a server_rec* in disguise. The following methods can be used on the server object:

$s->server_admin

Returns the mail address of the person responsible for this server.

$s->server_hostname

Returns the hostname used by this server.

$s->port

Returns the port that this servers listens too.

$s->is_virtual

Returns true if this is a virtual server.

$s->names

Returns the wild-carded names for HostAlias servers.

SETTING UP THE RESPONSE

The following methods are used to set up and return the response back to the client. This typically involves setting up $r->status(), the various content attributes and optionally some additional $r->header_out() calls before calling $r->send_http_header() which will actually send the headers to the client. After this a typical application will call the $r->print() method to send the response content to the client.

$r->send_http_header

Send the response line and all headers to the client.

This method will create headers from the $r->content_xxx() and $r->no_cache() attributes (described below) and then append the headers defined by $r->header_out (or $r->err_header_out if status indicates an error).

$r->get_basic_auth_pw

If the current request is protected by Basic authentication, this method will return 0, otherwise -1. The second return value will be the decoded password sent by the client.

   ($ret, $sent_pw) = $r->get_basic_auth_pw;

$r->note_basic_auth_failure

Prior to requiring Basic authentication from the client, this method will set the outgoing HTTP headers asking the client to authenticate for the realm defined by the configuration directive AuthName.

$r->handler( [$meth] )

Set the handler for a request. Normally set by the configuration directive AddHandler.

   $r->handler( "perl-script" );

$r->notes( $key, [$value] )

Return the value of a named entry in the Apache notes table, or optionally set the value of a named entry. This table is used by Apache modules to pass messages amongst themselves. Generally if you are writing handlers in mod_perl you can use Perl variables for this.

   $r->notes("MY_HANDLER", OK);
   $val = $r->notes("MY_HANDLER");

$r->subprocess_env( $key, [$value] )

Return the value of a named entry in the Apache subprocess_env table, or optionally set the value of a named entry. This table is used by Apache's mod_include. By setting some custom variables inside a perl handler it is possible to combine perl with mod_include nicely. If you say, e.g. in a PerlHeaderParserHandler

   $r->subprocess_env("MyLanguage", "de");

you can then write in your .shtml document:

   <!--#if expr="$MyLanguage = en" -->
   English
   <!--#elif expr="$MyLanguage = de" -->
   Deutsch
   <!--#else -->
   Sorry
   <!--#endif -->

$r->content_type( [$newval] )

Get or set the content type being sent to the client. Content types are strings like "text/plain", "text/html" or "image/gif". This corresponds to the "Content-Type" header in the HTTP protocol. Example of usage is:

   $previous_type = $r->content_type;
   $r->content_type("text/plain");

$r->content_encoding( [$newval] )

Get or set the content encoding. Content encodings are string like "gzip" or "compress". This correspond to the "Content-Encoding" header in the HTTP protocol.

$r->content_language( [$newval] )

Get or set the content language. The content language corresponds to the "Content-Language" HTTP header and is a string like "en" or "no".

$r->status( $integer )

Get or set the reply status for the client request. The Apache::Constants module provide mnemonic names for the status codes.

$r->status_line( $string )

Get or set the response status line. The status line is a string like "200 Document follows" and it will take precedence over the value specified using the $r->status() described above.

$r->headers_out

The $r->headers_out method will return a %hash of server response headers. This can be used to initialize a perl hash, or one could use the $r->header_out() method (described below) to retrieve or set a specific header value directly.

$r->header_out( $header, $value )

Change the value of a response header, or create a new one. You should not define any "Content-XXX" headers by calling this method, because these headers use their own specific methods. Example of use:

   $r->header_out("WWW-Authenticate" => "Basic");
   $val = $r->header_out($key);

$r->err_headers_out

The $r->err_headers_out method will return a %hash of server response headers. This can be used to initialize a perl hash, or one could use the $r->err_header_out() method (described below) to retrieve or set a specific header value directly.

The difference between headers_out and err_headers_out is that the latter are printed even on error, and persist across internal redirects (so the headers printed for ErrorDocument handlers will have them).

$r->err_header_out( $header, [$value] )

Change the value of an error response header, or create a new one. These headers are used if the status indicates an error.

   $r->err_header_out("Warning" => "Bad luck");
   $val = $r->err_header_out($key);

$r->no_cache( $boolean )

This is a flag that indicates that the data being returned is volatile and the client should be told not to cache it.

$r->print( @list )

This method sends data to the client with $r->write_client, but first sets a timeout before sending with $r->hard_timeout.

$r->send_fd( $filehandle )

Send the contents of a file to the client. Can for instance be used like this:

  open(FILE, $r->filename) || return 404;
  $r->send_fd(FILE);
  close(FILE);

$r->internal_redirect_handler( $newplace )

Redirect to a location in the server namespace without telling the client. For instance:

   $r->internal_redirect_handler("/home/sweet/home.html");

SERVER CORE FUNCTIONS

$r->soft_timeout($message)

$r->hard_timeout($message)

$r->kill_timeout

$r->reset_timeout

(Documentation borrowed from http_main.h)

There are two functions which modules can call to trigger a timeout (with the per-virtual-server timeout duration); these are hard_timeout and soft_timeout.

The difference between the two is what happens when the timeout expires (or earlier than that, if the client connection aborts) --- a soft_timeout just puts the connection to the client in an "aborted" state, which will cause http_protocol.c to stop trying to talk to the client, but otherwise allows the code to continue normally. hard_timeout(), by contrast, logs the request, and then aborts it completely --- longjmp()ing out to the accept() loop in http_main. Any resources tied into the request resource pool will be cleaned up; everything that is not will leak.

soft_timeout() is recommended as a general rule, because it gives your code a chance to clean up. However, hard_timeout() may be the most convenient way of dealing with timeouts waiting for some external resource other than the client, if you can live with the restrictions.

When a hard timeout is in scope, critical sections can be guarded with block_alarms() and unblock_alarms() --- these are declared in alloc.c because they are most often used in conjunction with routines to allocate something or other, to make sure that the cleanup does get registered before any alarm is allowed to happen which might require it to be cleaned up; they * are, however, implemented in http_main.c.

kill_timeout() will disarm either variety of timeout.

reset_timeout() resets the timeout in progress.

$r->register_cleanup($code_ref)

   $r->register_cleanup(sub {
       my $r = shift;
       warn "registered cleanup called for ", $r->uri, "\n";
   });

CGI SUPPORT

We also provide some methods that make it easier to support the CGI type of interface.

$r->cgi_env

Return a %hash that can be used to set up a standard CGI environment. Typical usage would be:

   %ENV = $r->cgi_env

NOTE: The $ENV{GATEWAY_INTERFACE} is set to 'CGI-Perl/1.1' so you can say:

   if($ENV{GATEWAY_INTERFACE} =~ /^CGI-Perl/) {
       # do mod_perl stuff
   }
   else {
       # do normal CGI stuff
   }

When given a key => value pair, this will set an environment variable.

   $r->cgi_env(REMOTE_GROUP => "camels");

$r->cgi_var($key);

Calls $r->cgi_env($key) in a scalar context to prevent the mistake of calling in a list context.

   my $doc_root = $r->cgi_env('DOCUMENT_ROOT');

$r->send_cgi_header()

Take action on certain headers including Status:, Location: and Content-type: just as mod_cgi does, then calls $r->send_http_header(). Example of use:

   $r->send_cgi_header(<<EOT);
   Location: /foo/bar
   Content-type: text/html 
   
   EOT

ERROR LOGGING

The following methods can be used to log errors.

$r->log_reason($message, $file)

The request failed, why?? Write a message to the server errorlog.

   $r->log_reason("Because I felt like it", $r->filename);

$r->log_error($message)

Uh, oh. Write a message to the server errorlog.

   $r->log_error("Some text that goes in the error_log");

$r->warn($message)

For pre-1.3 versions of apache, this is just an alias for log_error. With 1.3+ versions of apache, this message will only be send to the error_log if LogLevel is set to warn or higher.

UTILITY FUNCTIONS

Apache::unescape_url($string)

Handy function for unescapes. Use this one for filenames/paths. Use unescape_url_info for the result of submitted form data.

Apache::unescape_url_info($string)

Handy function for unescapes submitted form data. In opposite to unescape_url it translates the plus sign to space.

Apache::perl_hook($hook)

Returns true if the specified callback hook is enabled:

   for (qw(Access Authen Authz ChildInit Cleanup Fixup
           HeaderParser Init Log Trans Type))
   {
       print "$_ hook enabled\n" if Apache::perl_hook($_);
   }

AUTHORS

Gisle Aas <aas@sn.no> and Doug MacEachern <dougm@osf.org>

To install mod_perl, copy and paste the appropriate command in to your terminal.

cpanm

cpanm mod_perl

CPAN shell

perl -MCPAN -e shell
install mod_perl

For more information on module installation, please visit the detailed CPAN module installation guide.

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