NAME

HTML::Embperl - Perl extension for embedding Perl code in HTML documents

SYNOPSIS

Embperl is a Perl extension module which gives you the ability to embed Perl code in HTML documents, like server-side includes for shell commands.

DESCRIPTION

Embperl can operate in one of four modes:

Offline

Converts an HTML file with embedded Perl statements into a standard HTML file.

embpexec.pl [-o outputfile] [-l logfile] [-d debugflags] htmlfile [query_string]

htmlfile: The full pathname of the HTML file which should be processed by Embperl.
query_string: Optional. Has the same meaning as the environment variable QUERY_STRING when invoked as a CGI script. That is, QUERY_STRING contains everything following the first "?" in a URL. <query_string> should be URL-encoded. The default is no query string.
-o outputfile: Optional. Gives the filename to which the output is written. The default is stdout.
-l logfile: Optional. Gives the filename of the logfile. The default is /tmp/embperl.log.
-d debugflags: Optional. Specifies the level of debugging (what is written to the log file). The default is nothing. See below for exact values.

As a CGI script

Instead of a file being sent directly by the web server, the document is processed by the CGI script and the result is sent to the client.

embpexec.pl

If embpexec.pl is invoked without any parameters and the environment variable PATH_TRANSLATED is set, it runs itself as a CGI script. This means that form data is taken either from the environment variable QUERY_STRING or from stdin, depending on whether or not CONTENT_LENGTH is set. (This will be set by the web server depending on whether the request method is GET or POST). Input is taken from the file pointed to by PATH_TRANSLATED and the output is send to stdout. The logfile is generated at its default location, which is configurable via the environment variable EMBPERL_LOG.

To use this mode you must copy embpexec.pl to your cgi-bin directory. You can invoke it with the URL http://www.domain.xyz/cgi-bin/embpexec.pl/url/of/your/document.

The /url/of/your/document will be passed to Embperl by the web server. Normal processing (aliasing, etc.) takes place before the URI makes it to PATH_TRANSLATED.

If you are running the Apache httpd, you can also define embpexec.pl as a handler for a specific file extention or directory.

Example of Apache srm.conf:

<Directory /path/to/your/html/docs>
Action text/html /cgi-bin/embperl/embpexec.pl
</Directory>

From mod_perl (Apache httpd)

This works like the CGI-Script, but with the advantage that the script is compiled only once at server startup, where other one-time actions (such as opening files and databases) can take place. This will drastically reduce response times for the request. To use this you must compile Apache httpd with mod_perl and add HTML::Embperl as the PerlHandler.

Example of Apache srm.conf:

SetEnv EMBPERL_DEBUG 2285

Alias /embperl /path/to/embperl/eg

<Location /embperl/x>
SetHandler  perl-script
PerlHandler HTML::Embperl
Options     ExecCGI
</Location>

Another possible setup (for Apache 1.3bX see below) is

SetEnv EMBPERL_DEBUG 2285

<Files *.epl>
SetHandler  perl-script
PerlHandler HTML::Embperl
Options     ExecCGI
</files>

AddType text/html .epl

Don't forget the AddType. In this setup, all files ending with .epl are processed by Embperl.

NOTE: Since <Files> does not work the same in Apache 1.3bX as it does in Apache 1.2.x, you need to use <FilesMatch> instead.

<FilesMatch ".*\.epl$">
SetHandler  perl-script
PerlHandler HTML::Embperl
Options     ExecCGI
</FilesMatch>

See the section on debugging (dbgLogLink and EMBPERL_VIRTLOG) to find out how you can configure Embperl so you can view the log file with your browser!

By calling HTML::Embperl::Execute (\%param)

Execute takes a hash reference as argument. This gives the chance to vary the parameters according to the job that should be done. Possible items are:

inputfile

File which should be used as source. If input is also specified this parameter should give a unique name to identify the source. Everytime Embperl sees the same text in inputfile it assumes that you compile the same source, that means Embperl uses the same package name as in your last call and only recompiles the code if mtime has changed or is undefined.

input

Reference to a string which contains the source. inputfile must also be specified to give a name for the source. The name can be any text.

mtime

Last modification time of member input. If undef the code passed by input is always recompiled, else the code is only recompiled if mtime changes.

outputfile

File to which the output should be written. If neither outputfile nor output is specified ouput is written to stdout.

output

Reference to a scalar where the output should be written to.

cleanup

This value specifies if and when the cleanup of the package should be executed. (See variables scopes below for more information on cleanup)

cleanup = -1

Never cleanup the variables

cleanup = 0 or not specified

If running under mod_perl cleanup is delayed until the connection to the client is closed, so it does not enlarge the response time to the client. If the Execute function is called more the once before the end of the request all cleanups take place after the end of the request and not between calls of Execute.

If running as cgi or offline cleanup takes immediately place.

cleanup = 1

Immediate cleanup

options

Same as EMBPERL_OPTIONS (see below), except for cleanup.

debug

Same as EMBPERL_DEBUG (see below).

escmode

Same as EMBPERL_ESCMODE (see below).

package

Same as EMBPERL_PACKAGE (see below).

virtlog

Same as EMBPERL_VIRTLOG (see below). If virtlog is equal to uri the logfile is send.

uri

The URI of the request. Only needed for the virtlog feature.

compartment

Same as EMBPERL_COMPARTMENT (see below).

Helper functions for Execute

HTML::Embperl::Init ($Logfile): When not running under mod_perl, you must first do a call to Init before you can use Execute. Do not call Init when running under mod_perl!
HTML::Embperl::Term: Call this when your work is done.
HTML::Embperl::ScanEnvironement (\%params): Scans the %ENV and setups %params for use by Execute. All Embperl runtime configuration options are recognised, except EMBPERL_LOG.

EXAMPLES for Execute:

# Get source form /path/to/your.html and
# write output to /path/to/output'

HTML::Embperl::Execute ({ inputfile  => '/path/to/your.html',
                          outputfile => '/path/to/output'}) ;


# Get source from scalar and write output to stdout
# Don't forget to modify mtime if $src changes

$src = '<html><head><title>Page [+ $no +]</title></head>' ;

HTML::Embperl::Execute ({ inputfile  => 'some name',
                          input      => \$src,
                          mtime      => 1 }) ;

# Get source from scalar and write output another scalar

my $src = '<html><head><title>Page [+ $no +]</title></head>' ;
my $out ;

HTML::Embperl::Execute ({ inputfile  => 'another name',
                          input      => \$src,
                          mtime      => 1,
                          output     => \$out }) ;

print $out ;

Runtime configuration

The runtime configuration is done by setting environment variables, either on the command line (when working offline) or in your web server's configuration file. Most HTTP servers understand

SetEnv <var> <value>

If you are using Apache and mod_perl you can use

PerlSetEnv <var> <value>

The advantage of PerlSetEnv over SetEnv is that it can be used on a per directory/virtual host basis.

EMBPERL_COMPARTMENT

Gives the name of the compartment from which to take the opcode mask. (See the chapter about Safe namespaces for more details.)

EMBPERL_ESCMODE

Specifies the initial value for $escmode (see below).

EMBPERL_LOG

Gives the location of the log file. This will contain information about what Embperl is doing. How much information depends on the debug settings (see below). The log output is intended to show what your embedded Perl code is doing and to help debug it. Default is /tmp/embperl.log.

NOTE: When running under mod_perl you need to use PerlSetEnv for setting the logfile path, and mod_perl >= 1.07_03 if you load Embperl at server startup (with PerlScript or PerlModule).

EMBPERL_PACKAGE

The name of the package where your code will be executed. By default Embperl generates a unique package name for every file. This ensures that variables and functions from one file can not affect those from another file. (Any package's variables will still be accessible with explict package names.)

EMBPERL_VIRTLOG

Gives a virtual location where you can access the Embperl logfile with a browser. This feature is disabled (default) if EMBPERL_VIRTLOG is not specified. See also dbgLogLink for an Example how to set it up in your srm.conf.

EMBPERL_OPTIONS

This bitmask specifies some options for the execution of Embperl:

optDisableVarCleanup = 1

Disables the automatic cleanup of variables at the end of each request.

optDisableEmbperlErrorPage = 2

Tells Embperl to not send its own errorpage in case of failure, instead giving the error back to the web server and let the web server handle it the standard way. Without this option, Embperl sends its own error page, showing all the errors which have occured. If you have dbgLogLink enabled, every error will be a link to the corresponding location in the log file.

optSafeNamespace = 4

Tells Embperl to execute the embbeded code in a safe namespace so the code cannot access data or code in any other package. (See the chapter about Safe namespaces below for more details.)

optOpcodeMask = 8

Tells Embperl to aply an operator mask. This gives you the chance to disallow special (unsafe) opcodes. (See the Chapter about Safe namespaces below for more details.)

optRawInput = 16

Causes Embperl not to preprocess the source for a Perl expression. (The only exception is that carriage returns will be removed, as Perl does not like them.) This option should be set when you writing your code with an ASCII editor.

If you using a WYSIWYG editor which inserts unwanted HTML tags in your Perl expressions and escapes special charcaters automatically (e.g., `<' appears as `<' in the source), you should not set this option. Embperl will automaticly convert the HTML input back to the Perl expressions as you wrote them.

EMBPERL_DEBUG

This is a bitmask which specifies what should be written to the log. The following values are defined:

dbgStd = 1

Show minimum information.

dbgMem = 2

Show memory and scalar value allocation.

dbgEval = 4

Show arguments to and results of evals.

dbgCmd = 8

Show metacommands and HTML tags which are processed.

dbgEnv = 16,

List every request's environment variables.

dbgForm = 32

Lists posted form data.

dbgTab = 64

Show processing of dynamic tables.

dbgInput = 128

Show processing of HTML input tags.

dbgFlushOutput = 256

Flush Embperl's output after every write. This should only be set to help debug Embperl crashes, as it drastically slows down Embperl's operation.

dbgFlushLog = 512

Flush Embperl's logfile output after every write. This should only be set to help debug Embperl crashes, as it drastically slows down Embperl's operation.

dbgAllCmds = 1024

Logs all commands and HTML tags, whether or not they are really excuted or not. (It logs a `+' or `-' to tell you if they are executed.)

dbgSource = 2048

Logs the next piece of the HTML source to be processed. (NOTE: This generates a lot of output!)

dbgFunc = 4096

This is only anvailable when Embperl is compiled with -DEPDEBUGALL, and it normally only used for debugging Embperl itself. Records all function entries to the logfile.

dbgLogLink = 8192

Inserts a link at the top of each page which can be used to view the log for the current HTML file. See also EMBEPRL_VIRTLOG.

Example:

SetEnv EMBPERL_DEBUG 10477
SetEnv EMBPERL_VIRTLOG /embperl/log

<Location /embperl/log>
SetHandler perl-script
PerlHandler HTML::Embperl
Options ExecCGI
</Location>

dbgDefEval = 16384

Shows every time new Perl code is compiled.

dbgCacheDisable = 32768

Disables the use of the p-code cache. All Perl code is recompiled every time. (This should not be used in normal operation as it slows down Embperl dramatically.) This option is only here for debugging Embperls cache handling. There is no guarantee, that Embperl behaves the same with and without cache (actually is does not!)

dbgEarlyHttpHeader = 65536

Normally, HTTP headers are sent after a request is finished without error. This gives you the chance to set arbitrary HTTP headers within the page, and Embperl the chance to calculate the content length. To do this, all the output is kept in memory until the HTTP headers are sent, and then the document is sent. This flag will cause the HTTP headers to be sent before the script is processed, and the script's output will be sent directly. (Embperl versions before 0.18 did not have this option; all headers were sent early.)

dbgHeadersIn = 262144

Log all HTTP headers which are sent from the browser.

dbgShowCleanup = 524288

Show every variable which is undef'd at the end of the request. For scalar variables, the value before undef'ing is logged.

A good value to start is 2285 or 10477 if you want to view the logfile with your browser. (Don't forget to set EMBPERL_VIRTLOG.) If Embperl crashes, add 512 so the logfile is flushed after every line is written and you can see where Embperl is when it crashes.

SYNTAX

Embperl understands four categories of commands. The first three are special Embperl commands, and the last category are some HTML tags that can trigger special processing. Embperl commands can span multiple lines and need not start or end at a line boundary.

Before the special Embperl commands are processed, and for the VALUE attribute of the INPUT tag (see below), all HTML tags are removed and special HTML characters are translated to their ASCII values (e.g., `<' is translated to `<'). You can avoid from this behavior by preceding the special character or HTML tag with a backslash. This is done in case your favorite (WYSIWYG) HTML editor inserts tags like line breaks or formatting into your Embperl commands where you don't want them.

NOTE: If you do use an ASCII editor to write your HTML documents, you should set the option optRawInput so Embperl does not preprocess your source. You can also HTML-escape your code (i.e. write `<' instead of `<'), to avoid ambiguity. In most cases it will also work without the optRawInput and HTML-escaping, but in some cases Embperl will deteced an HTML tag were there isn't one.

All Embperl commands start with a `[' and end with a `]'. To get a real `[' you must enter `[['.

Embperl does not use SGML comments (i.e., <! ... !> or similar things) because some HTML editors can't create them, or it's much more complicated. Sinces every HTML editor takes (or should take) `[' and `]' as normal text, there should be no problem.

[+ Perl code +]

Replace the command with the result of evaluating the Perl code. The Perl code can be anything which can be used as an argument to Perl eval statement. (See Security below for restrictions.) Examples:

[+ $a +]        Replaces the [+ $a +] with the content of
                the variable $a

[+ $a+1 +]      (Any expression can be used)

[+ $x[$i] +]    (Arrays, hashes, and more complex
                 expressions work)

NOTE: Whitespace is ignored. The output will be automatically HTML-escaped (e.g., `<' is translated to `<') depending on the value of the variables $escmode. You do not have to worry about it.

[- Perl code -]

Executes the Perl code, but delete the whole command from the HTML output.

Examples:

[- $a=1 -]            Set the variable $a to one.
		       No output will be generated.

[- use SomeModule -]  You can use other modules.

[- $i=0; while ($i<5) {$i++} -]  Even more complex
                                 statements or multiple
                                 statements are possible.

NOTE: Statements like if, while, for, etc., must be contained in a single Embperl command. You cannot have the if in one command block and the terminating `}' or else in another.

NOTE: To define subroutines, use [! ... !] (see below) instead of [- ... -] to avoid recompilation of the subroutine on every request.

[! Perl Code !]

Same as [- Perl Code -] with the exception that the code is only executed at the first request. This could be used to define subroutines, or do one-time initialization.

[$ Cmd Arg $]

Execute an Embperl metacommand. Cmd can be one of the following. (Arg varies depending on <Cmd>).

if, elsif, else, endif

Everything following the if metacommand until the else, elsif, or endif is only output if the Perl expression given in Arg is true. else and elsif work similarly.

Example:

[$ if $ENV{REQUEST_METHOD} eq 'GET' $]
Method was GET<BR>
[$ else $]
Method other than GET used<BR>
[$ endif $]

This will send one of the two sentences to the client, depending on the request method used to retrieve the document.

while, endwhile

Executes a loop until the Arg given to while is false.

Example: (see eg/x/while.htm)

[- $i = 0; @k = keys %ENV -]
[$ while ($i &lt; $#k) $]
[+ $k[$i] +] = [+ $ENV{$k[$i]} +]<BR>
[- $i++ -]
[$ endwhile $]

This will send a list of all environment variables to the client.

NOTE: The `<' is translated to `<' before call the Perl eval, unless optRawInput is set.

hidden

Arg consists of zero, one or two names of hashes (with or without the leading %) and an optional array as third parameter. The hidden metacommand will generated hidden fields for all data contained in first hash and not in second hash. The default used for the first hash is %fdat, %idat for the second.

If the third parameter is specified, the fields are written in the order they appear in this array. That is, all keys of the first hash must be in this array properly sorted. This is intended for situations where you want to pass data from one form to the next, for example, two forms which should be filled one after the other. (Examples might be an input form and a second form to review and accept the input, or a Windows-style "wizard"). Here you can pass along data from previous forms in hidden fields. (See eg/x/neu.htm for an example.) If you use just the hidden command without parameters, it simply generates hidden fields for all form fields submitted to this document which aren't already contained in another input field.

Example:

    <FORM ACTION="inhalt.htm" METHOD="GET">
	<INPUT TYPE="TEXT" NAME="field1">
    [$ hidden $]
    </FORM>

If you request this with

http://host/doc.htm?field1=A&field2=B&field3=C

the output will be

    <FORM ACTION="inhalt.htm" METHOD="GET">
	<INPUT TYPE="TEXT" NAME="feld1" VALUE="A">
	
    <INPUT TYPE="HIDDEN" NAME="field2" VALUE="B">
    <INPUT TYPE="HIDDEN" NAME="field3" VALUE="C">
    </FORM>

NOTE: This should only be used for small amount of data, since the hidden fields are sent to the browser, which sends it back with the next request. If you have a large amount of data, store it in a file with a unique name and send only the filename in a hidden field. Be aware of the fact that the data could be change by the browser if the user didn't behave exactly as you expect. Your program should handle such situations properly.

var

The var command declares one or more variables for use within this Embperl document and sets the strict pragma. The variable names must be supplied as space separated list.

Example:

[$var $a %b @c $]

This is the same as writing the following in normal Perl code:

use strict ;
use vars qw($a %b @c) ;

NOTE 1: `use strict' within an Embperl document will only aply to the block where it occurs.

HTML Tags

Embperl recognizes the following HTML tags specially. All other are simply passed through, as long as they are not part of a Embperl command.

TABLE, /TABLE, TR, /TR

Embperl can generate dynamic tables (one or two dimensional). You only need to specify one row or column.

Embperl generates as many rows or columns as necessary. This is done by using the magic variables $row, $col, and $cnt. If you don't use $row/$col/$cnt within a table, Embperl does nothing and simply passes the table through.

Embperl checks if any of $row, $col, or $cnt is used. Embperl repeats all text between <table> and </table>, as long the expressions in which $row or $cnt occurs is/are defined.

Embperl repeats all text between <tr> and </tr>, as long the expressions in which $col or $cnt occurs is/are defined.

See also $tabmode (below) for end-of-table criteria.

Examples: (see eg/x/table.htm for more examples)

[- @k = keys %ENV -]
<TABLE>
    <TR>
        <TD>[+ $i=$row +]</TD>
        <TD>[+ $k[$row] +]</TD>
        <TD>[+ $ENV{$k[$i]} +]</TD>
    </TR> 
</TABLE>

This will show all entries in array @k (which contains the keys from %ENV), so the whole environment is displayed (as in the while example), with the first column containing the zero-based index, the second containing the content of the variable name, and the third the environment variable's value.

This could be used to display the result of database query if you have the result in an array. You may provide as many columns as you need. It is also possible to call a fetch subroutine in each table row.

TH, /TH

The TH tag is interpreted as table heading. If the whole row is made of <TH> </TH> instead of <TD> </TD> it's treated as column heading. Everything else will be treated as row headings in the future, but is ignored in the current version.

DIR, MENU, OL, UL, DL, SELECT, /DIR, /MENU, /OL, /UL, /DL, /SELECT

Lists and dropdowns or list boxes are treated exactly as one- dimensional tables. Only $row, $maxrow, $col, $maxcol and $tabmode are honored. $col and $maxcol are ignored. See eg/x/lists.htm for an example.

OPTION

Embperl checks if there is a value from the form data for a specific option in a menu. If so, this option will be preselected.

Example:

<FORM METHOD="POST"> <P>Select Tag</P>

If you request this document with list.htm?SEL1=x
you can specify that the element which has a value
of x is initialy selected

<P><SELECT NAME="SEL1">
   <OPTION VALUE="[+ $v[$row] +]">
      [+ $k[$row] +]
   </OPTION>
</SELECT></P>
</FORM>

INPUT

The INPUT tag interacts with the hashes %idat und %fdat. If the input tag has no value, and a key exists with the same text as the NAME attribute of the input tag, Embperl will generate a VALUE attribute with the corresponding value of the hash key.

All values of <INPUT> tags are stored in the hash %idat, with NAME as the hash key and VALUE as the hash value. Special processing is done for TYPE=RADIO and TYPE=CHECKBOX. If the VALUE attribute contains the same text as the value of the hash the CHECKED attribute is inserted, else it is removed. So if you specify as the ACTION URL the file which contains the form itself, the form will be redisplayed with same values as entered the first time. (See eg/x/neu.htm for an example.)

TEXTAREA, /TEXTAREA

The TEXTAREA tag is treated excatly like other input fields.

Variable scope and cleanup

The scope of a variable declared with my or local ends at the end of the enclosing [+/- ... -/+] block; the [+/- ... -/+] blocks act much like Perl's { ... } in that regard.

Global variables (everything not declared with my or local) will be undef'ed at the end of each request, so you don't need to worry about any old variables laying around and causing suspicous results. This is only done for variables in the package the code is evaled in-- every variable that does not have an explicit package name. All variables with an explicit package name (i.e., in modules you use) will stay valid until the httpd child process dies. Embperl will change the current package to unique name for every document, so the influence between different documents is kept to a minimum. You can set the name of the package with EMBPERL_PACKAGE. (See also Safe namespaces.)

Since a CGI scripts is always a process of its own, you don't need to worry about that when you use Embperl as a CGI script.

If you need to declare variables which live more the one HTTP request (for example, a database handle), you must declare then in another package (i.e., $Persistent::handle instead of $handle).

If you use the strict pragma, you can use the var metacommand to declare your variables.

NOTE: Bacause Apache::DBI has its own namespace this module will work together with Embperl to maintain your persistent database connection.

You can disable the automatic cleanup of global variables with EMBPERL_OPTIONS or the cleanup parameter of the Execute function.

If you like to do your own cleanup you can define a subroutine CLEANUP in your document. This will called right before the variables will be cleaned up, but after the connection to the client is closed.

EXAMPLE:

 [! sub CLEANUP { close FH ; } !]

Predefined variables

Embperl has some special variables which have a predefined meaning.

%ENV

Contains the environment as seen from a CGI script.

%fdat

Contains all the form data sent to the script by the calling form. The NAME attribute builds the key and the VALUE attribute is used as the hash value. Embperl doesn't care if it's called with the GET or POST method, but there may be restrictions on the length of parameters using GET--not from Embperl, but perhaps from the web server, especially if you're using Embperl's CGI mode--do it's safer to use POST.

Embperl also supports ENCTYPE multipart/form-data, which is used for file uploads. The entry in %fdat corresponding to the file field will be a filehandle, as with CGI.pm. (Embperl uses CGI.pm internally to process forms encoded with multipart/form-data.)

File upload example:

  HTML page:

    <FORM METHOD="POST" ENCTYPE="multipart/form-data">
      <INPUT TYPE="FILE" NAME="ImageName">
    </FORM>

  Embperl ACTION:

    [- if (defined $fdat{ImageName}) {
         open FILE, "> /tmp/file.$$";
	 print FILE $buffer
           while read($fdat{ImageName}, $buffer, 32768);
         close FILE;
       }
    -]

@ffld

Contains all the field names in the order in which they were sent by the browser. This is normally--but not necessarily--the order in which they appear in your form.

%idat

Contains all the values from all input tags processed so far.

$row, $col

Row and column counts for use in dynamic tables. (See HTML tag table.)

$maxrow, $maxcol

Maxium number of rows or columns to display in a table. To prevent endless loops, $maxrow defaults to 100 and $maxcol to 10. (See HTML tag table.)

$cnt

Contains the number of table cells displayed so far. (See HTML tag table.)

$tabmode

Determines how the end of a dynamic table is detected:

end of table

1: End when an expression with $row becomes undefined. The row containing the undefined expression is not displayed.
2: End when an expression with $row becomes undefined. The row containing the undefined expression is displayed.
4: End when $maxrow rows have been displayed.

end of row

16: End when an expression with $col becomes undefined. The column containing the undefined expression is not displayed.
32: End when an expression with $col becomes undefined. The column containing the undefined is displayed.
64: End when $maxcol columns have been displayed.

The default is 17, which is correct for all sort of arrays. You should rarely need to change it. The two values can be added together.

$escmode

Turn HTML and URL escaping on and off. The default is on ($escmode = 3).

$escmode = 3: The result of a Perl expression is HTML-escaped (e.g., `>' becomes `>') in normal text and URL-escaped (e.g., `&' becomes `%26') within an <A> tag.
$escmode = 2: The result of a Perl expression is always URL-escaped (e.g., `&' becomes `%26').
$escmode = 1: The result of a Perl expression is always HTML-escaped (e.g., `>' becomes `>').
$escmode = 0: No escaping takes place.

$req_rec

This variable is only available when running under control of mod_perl. It contains the request record needed to access the Apache server API. See perldoc Apache for more information.

LOG

This is the filehandle of the Embperl logfile. By writing `print LOG "something"' you can add lines to the logfile. NOTE: The logfile line should always start with the pid of the current process and continue with a four character signature delimited by a ':', which specifies the log reason.

Example: print LOG "[$$]ABCD: your text\n" ;

If you are writing a module for use under Embperl you can say

tie *LOG, 'HTML::Embperl::Log';

to get a handle by which you can write to the Embperl logfile.

Namespaces and opcode restrictions

Since most web servers will contain more than one document, it is necessary to protect the documents against each other. Embperl does this by using Perl namespaces. By default, Embperl executes every document in its own namespace (package). This will prevent documents from accidentally overriding the others' data. You can change this behavior (or simply the package name) with the configuration directive EMBPERL_PACKAGE. NOTE: By explicitly specifing a package name, you can access data that is used by another document.

If Embperl is used by more then one person, it may be neccessary to really protect one document from each other. To do this, Embperl gives you the option to use safe namespaces. Each document runs in its own package and can't access anything outside of this package. (See the documentation of Safe.pm for a more detailed discusion about safe namespaces.)

To make a document run in a safe namespace, simply add optSafeNamespace to EMBPERL_OPTIONS. The default package name used is the same as in normal operation and can be changed with EMBPERL_PACKAGE. NOTE: From the perspective of the document being executed, the code is running in the package main!

A second option to make Embperl more secure is the use of the opcode restriction mask. Before you can use the opcode mask, you must set up a safe compartement.

B<$cp = HTML::Embperl::AddCompartment($name);>

This will create a new compartment with a default opcode mask and the name $name. (The name is used later to tell Embperl which compartment to use.) Now you can change the operator mask. For example:

B<$cp->deny(':base_loop');>

In your configuration you must set the option optOpcodeMask in EMBPERL_OPTIONS and specify from which compartment the opcode mask should be taken by setting EMBPERL_COMPARTMENT.

Example (for use with mod_perl):

   B<srm.conf:>

   PerlScript startup.pl

   SetEnv EMBPERL_DEBUG 2285

   Alias /embperl /path/to/embperl/eg

   <Location /embperl/x>
   SetHandler perl-script
   PerlHandler HTML::Embperl
   Options ExecCGI
   PerlSetEnv EMBPERL_OPTIONS 12
   PerlSetEnv EMBPERL_COMPARTMENT test
   </Location>

   B<startup.pl:>

   $cp = HTML::Embperl::AddCompartment('test');
   $cp->deny(':base_loop');

This will execute the file startup.pl on server startup. startup.pl sets up a compartment named `test', which will have a default opcode mask and additionaly, will have loops disabled. Code will be executed in a safe namespace.

NOTE: The package name from the compartment is NOT used!

Look at the documentation of Safe.pm and Opcode.pm for more detailed information on how to set opcode masks.

UTILITY FUNCTIONS

AddCompartment($Name)

Adds a compartment for use with Embperl. Embperl only uses the opcode mask from it, not the package name. AddCompartement return the newly- created compartment so you can allow or deny certain opcodes. See the Safe.pm documentation for details of setting up a compartment. See chapter about Safe namepsaces for details of how Embperl uses it.

Example:

$cp = HTML::Embperl::AddCompartment('TEST');
$cp->deny(':base_loop');

MailFormTo($MailTo, $Subject)

Sends the content of the hash %fdat in the order specified by @ffld to the given $MailTo addressee, with a subject of $Subject.

If you specifiy the following example code as the action in your form

<FORM ACTION="x/feedback.htm" METHOD="POST"
      ENCTYPE="application/x-www-form-urlencoded">

The content of the form will be mailed to the given email address.

Example:

<HTML>
<HEAD>
<TITLE>Feedback</TITLE>
</HEAD>
<BODY>
       [- MailFormTo('webmaster@domain.xy',
                     'Mail from WWW Form') -]
       Your data has been sccesfully sent!
</BODY>
</HTML>

NOTE: You must have Net::SMTP (from the libnet package) installed to use this function.

PERFORMANCE

To get the best performace from Embperl, it is necessary to restrict logging to a minimum. You can drastically slow down Embperl if you enable all logging options. (This is why `make test' takes a while to run.) You should never enable dbgFlushOutput, dbgFlushLog or dbgCacheDisable in a production environment. More debugging options are useful for developement where it doesn't matter if the request takes a little bit longer, but on a heavily-loaded server they should be disabled.

Also take a look at mod_perl_tuning.pod for general ideas about performance.

BUGS

None known.

Under perl5.004 there are memory leaks. This is not an Embperl bug, but can cause your httpd to grow endlessly when running under mod_perl. Please upgrade to perl5.004_04 to fix this. You should also upgrade to a mod_perl version higher than 1.07_01 as soon as possible, because until 1.07_01 there is a memory leak in Apache->push_handler.

FEEDBACK and BUG REPORTS

Please let me know if you use or test this module. Bugs, questions, suggestions for things you would find useful, etc., are discussed on the mod_perl mailling list.

>From the mod_perl README:

For comments, questions, bug-reports, announcements, etc., join the Apache/Perl mailing list by sending mail to listserv@listproc.itribe.net with the string "subscribe modperl" in the body.

There is a hypermail archive for this list available from: http://outside.organic.com/mail-archives/modperl/

SUPPORT

You can get free support on the mod_perl mailing list (see above). If you need commercial support (with a guarantee for response time or a solution) for Embperl or want a web site where you can run your Embperl/mod_perl scripts without setting up your own web server, please send email to info@ecos.de.

REFERENCES

mod_perl            http://perl.apache.org/
mod_perl FAQ        http://perl.apache.org/faq
Embperl             http://perl.apache.org/embperl.html
apache web server   http://www.apache.org/
see also            http://www.perl.com/CPAN/modules/by-module/Apache/apache-modlist.html

AUTHOR

G. Richter (richter@dev.ecos.de)

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NAME

SYNOPSIS

DESCRIPTION

Helper functions for Execute

EXAMPLES for Execute:

Runtime configuration

SYNTAX

Variable scope and cleanup

Predefined variables

Namespaces and opcode restrictions

UTILITY FUNCTIONS

PERFORMANCE

BUGS

FEEDBACK and BUG REPORTS

SUPPORT

REFERENCES

AUTHOR

SEE ALSO

Module Install Instructions