<?xml version="1.0"?>
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/><title>maildropfilter</title><link rel="stylesheet" type="text/css" href="style.css"/><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"/><link rel="home" href="#idm46044390010000" title="maildropfilter"/><link xmlns="" rel="stylesheet" type="text/css" href="manpage.css"/><meta xmlns="" name="MSSmartTagsPreventParsing" content="TRUE"/><link xmlns="" rel="icon" href="icon.gif" type="image/gif"/><!--

Copyright 1998 - 2009 Double Precision, Inc.  See COPYING for distribution
information.

--></head><body><div class="refentry"><a id="idm46044390010000" shape="rect"> </a><div class="titlepage"/><div class="refnamediv"><h2>Name</h2><p>maildropfilter — maildrop's filtering language</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="informalexample"><p>
	<code class="filename">@withetcdir@/maildroprc</code>,
	<code class="filename">$HOME/.mailfilter</code>,
	<code class="filename">$HOME/.mailfilters/*</code>, and friends...
      </p></div></div><div class="refsect1"><a id="idm46044394451088" shape="rect"> </a><h2>DESCRIPTION</h2><p>
      This manual page describes the language used by <span class="command"><strong>maildrop</strong></span>
      to filter E-mail messages.
      The mail filtering instructions are read from a file.

      The language is loosely structured, it is based on pattern
      matching. The language has a distinct lexical and syntactical structure,
      very similar to Perl's, but it is important to note that it is not Perl,
      and is very different from Perl, in certain cases.</p><p>
      If the filtering instructions do not exist,
      <span class="command"><strong>maildrop</strong></span> delivers the
      message to the default mailbox without doing any additional processing,
      making it indistinguishable from the usual mail delivery agent.</p><p>
      It is important to note that <span class="command"><strong>maildrop</strong></span> reads and parses the
      <code class="systemitem">filter file</code> before doing anything. If there are any errors
      <span class="command"><strong>maildrop</strong></span> prints an error message, and terminates with the exit code
      set to <span class="errorcode">EX_TEMPFAIL</span>. A compliant mail transport agent
      should
      re-queue the message for a later delivery attempt. Hopefully, most simple
      syntax errors will not cause mail to be bounced back if the error is caught
      and fixed quickly.</p><div class="refsect2"><a id="idm46044394503184" shape="rect"> </a><h3>Environment</h3><p>
	<a id="environment" shape="rect"> </a>

	<span class="command"><strong>maildrop</strong></span> uses variables to access and manipulate messages.
	Variables
	are arbitrary text accessed by referring to the name of the variable, such as
	<code class="varname">HOME</code>, or <code class="varname">DEFAULT</code>.
	Text is placed into a variable by
	using an assignment statement, such as:
      </p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
FILE="IN.junk"
	  </pre></div></blockquote></div><p>
	This statement puts the text "IN.junk" (without the quotes) into a variable
	whose name is <code class="varname">FILE</code>.
	Later, the contents of a variable are accessed by using
	the $ symbol and the name for the variable. For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
to $FILE
	  </pre></div></blockquote></div><p>
	This will deliver the current message to the mailbox file (or a maildir
	directory) named "IN.junk".</p><p>
	<span class="command"><strong>maildrop</strong></span> initially creates variables from the environment
	variables
	of the operating system, UNLESS <span class="command"><strong>maildrop</strong></span> runs in delivery mode.
	Each
	operating system environment variable becomes a <span class="command"><strong>maildrop</strong></span>
	variable.
	When running in delivery mode, <span class="command"><strong>maildrop</strong></span> does not import the
	environment for security reasons,
	except for the environment variables that define the process locale
	(<code class="varname">LANG</code>,
	<code class="varname">LANGUAGE</code>, and
	<code class="varname">LC_<em class="replaceable"><code>*</code></em></code>), which are still imported.
      </p><p>
	In all cases <span class="command"><strong>maildrop</strong></span> resets the
	following variables to their default values: <code class="varname">HOME</code>,
	<code class="varname">DEFAULT</code>, <code class="varname">SHELL</code>,
	<code class="varname">PATH</code>, <code class="varname">LOCKEXT</code>,
	<code class="varname">LOCKREFRESH</code>, <code class="varname">LOCKSLEEP</code>,
	<code class="varname">LOCKTIMEOUT</code>, <code class="varname">MAILDIRQUOTA</code>,
	<code class="varname">SENDMAIL</code> and <code class="varname">LOGNAME</code>.</p><p>
	There's one exception to this rule which applies to the version of
	<span class="command"><strong>maildrop</strong></span> that comes with the
	<a class="ulink" href="http://www.courier-mta.org/" target="_top" shape="rect"><span class="application">Courier</span> mail server</a>.  The following
	does not apply to the standalone version of <span class="command"><strong>maildrop</strong></span>:
	when running in
	delivery mode, if the <code class="option">-d</code> flag was not used, or if it specifies
	the same userid as the one that's running <span class="command"><strong>maildrop</strong></span>:
	the following
	variables are automatically imported from the environment: <code class="varname">HOME</code>, <code class="varname">SHELL</code>,
	<code class="varname">LOGNAME</code> and <code class="varname">MAILDIRQUOTA</code>.
	These environment variables are
	initialized by the <span class="application">Courier</span>
	mail server prior to running <span class="command"><strong>maildrop</strong></span>.
	Additionally, the
	initial value for the <code class="varname">DEFAULT</code> maildrop variable is imported from
	the <code class="varname">MAILDROPDEFAULT</code> environment variable. This is because
	the <span class="application">Courier</span> mail server overloads the
	DEFAULT environment variable to store the defaulted
	portion of the local mailbox address. See the <a class="ulink" href="dot-courier.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">dot-courier</span>(5)</span></a> man page in the
	<span class="application">Courier</span> mail server
	distribution. You can get the <span class="application">Courier</span>
	mail server's <code class="varname">DEFAULT</code> value by
	using the
	<span class="command"><strong>import</strong></span> command.
	Note, however, that this will clobber the old
	contents of <code class="varname">DEFAULT</code>, which is probably not what you want.
	The right way to do this would be something like this:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
SAVEDEFAULT=$DEFAULT
import DEFAULT
LOCALDEFAULT=$DEFAULT
DEFAULT=$SAVEDEFAULT
	  </pre></div></blockquote></div><p>All internal variables are exported back as environment variables when
	<span class="command"><strong>maildrop</strong></span> runs an external command. Changes to internal variables, made
	by the <code class="systemitem">filter file</code>, are reflected in the exported environment.</p></div><div class="refsect2"><a id="idm46044394616512" shape="rect"> </a><h3>Lexical structure</h3><p>
	Most whitespace is generally ignored. The <span class="token">#</span>
	character introduces a comment
	running to the end of the line, which is also ignored. Unlike other mail
	filters, <span class="command"><strong>maildrop</strong></span> parses the
	<code class="systemitem">filter file</code> before taking any action
	with the message.
	If there are syntax errors in the file, <span class="command"><strong>maildrop</strong></span> displays
	an error message, and returns <span class="errorcode">EX_TEMPFAIL</span>. That should
	cause the
	mail message to remain in the queue, and, hopefully allow the problem to be
	corrected, without bouncing any mail.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	  In <span class="command"><strong>maildrop</strong></span>, the end of line is a lexical token. In order to
	  continue a long statement on the next line, terminate the line with a
	  backslash character.</p></div></div><div class="refsect2"><a id="idm46044394609984" shape="rect"> </a><h3>Literal text</h3><p>
	Literal text in the <span class="command"><strong>maildrop</strong></span> filtering language is
	surrounded by
	either single or double quotes. In order to enter a single quote into a text
	literal surrounded by single quotes, or a double quote into a literal
	surrounded by double quotes, prefix it with a backslash character. Use two
	backslash characters characters to enter one backslash character in the text
	literal.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>A backslash followed by either a backslash, or a matching quote, is
	  the only situation where the backslash character is actually removed, leaving
	  only the following character in the actual text literal. If a backslash
	  character is followed by any other character, the backslash is NOT
	  removed.</p></div><p>Multiple text literals in a row are automatically concatenated, even if
	they use different quotes. For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
FOOBAR="Foo"'bar'
	  </pre></div></blockquote></div><p>
	This sets the variable <code class="varname">FOOBAR</code> to the text "Foobar".
      </p></div><div class="refsect2"><a id="idm46044394590768" shape="rect"> </a><h3>Variable substitution</h3><p>
	<a id="varsubst" shape="rect"> </a>

	Variable substitution is performed on text literals that's surrounded by
	double quotation marks. The "<span class="token">$</span>" character, followed by a variable name,
	is replaced by that variable's contents.
      </p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
MAILBOX="$HOME/Mailbox"
	  </pre></div></blockquote></div><p>
	This sets the variable <code class="varname">MAILBOX</code> to the contents of the
	variable
	<code class="varname">HOME</code> followed by <code class="literal">"/Mailbox"</code>.
	Variable names must begin with an
	uppercase letter, a lowercase letter, or an underscore.
	Following that, all
	letters, digits, and underscores are taken as a variable name, and its
	contents replace the <span class="token">$</span> sign, and the variable name. It is possible to access
	variables whose name includes other characters, by using braces as
	follows:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
MAILBOX="${HOME-WORD}/Mailbox"
	  </pre></div></blockquote></div><p>
	Inserts the contents of the <code class="varname">HOME-WORD</code> variable. If the
	variable
	does not exist, the empty text literal is used to replace the variable name.
	It is not possible to access variables whose names include the <span class="token">}</span>
	character.</p><p>If the <span class="token">$</span> character is not followed by a left brace, letter, or an
	underscore, the <span class="token">$</span> character remains unmolested in the text literal. A
	backslash followed by the <span class="token">$</span> character results in a <span class="token">$</span> character in the text
	literal, without doing any variable substitution.</p><p>
	Variable substitution is not done in text literals which are surrounded by
	single quotes (apostrophes).</p></div><div class="refsect2"><a id="idm46044394578784" shape="rect"> </a><h3>Command line arguments</h3><p>
	<span class="command"><strong>maildrop</strong></span> initializes special variables:
	<code class="varname">$1</code>, <code class="varname">$2</code>, and so on, with
	additional parameters specified on the <span class="command"><strong>maildrop</strong></span>
	command line. A <code class="systemitem">filter file</code>
	may use those variables just like any other variables.</p></div><div class="refsect2"><a id="idm46044394574208" shape="rect"> </a><h3>Predefined variables</h3><a id="predefined" shape="rect"> </a><p>
	The following variables are automatically defined by
	<span class="command"><strong>maildrop</strong></span>. The
	default values for the following variables may be changed by the system
	administrator. For security reasons, the values of the following variables
	are always reset to their default values, and are never imported from the
	environment:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="varname">DEFAULT</code></span></dt><dd><p>The default mailbox to deliver the message to.
	      If the <code class="systemitem">filter file</code> does not indicate a mailbox to deliver this message
	      to, the message is delivered to this mailbox. The default mailbox is
	      defined by the system administrator.

	</p></dd><dt><span class="term"><code class="varname">FROM</code></span></dt><dd><p>Message envelope sender. This is usually the same
	      address as what appears in the <code class="literal">From:</code> header, but may
	      not be.
	      This information may or may not be available to <span class="command"><strong>maildrop</strong></span> on your
	      system. The message envelope sender is usually specified with the <code class="option">-f</code>
	      option to <span class="command"><strong>maildrop</strong></span>. If the <code class="option">-f</code> option is not given, <span class="command"><strong>maildrop</strong></span>
	      looks for the <code class="literal">Return-Path:</code> header in the message. As the last resort,
	      <code class="literal">FROM</code> defaults to <span class="quote">“<span class="quote">MAILER-DAEMON</span>”</span>.
	      Note that <code class="varname">FROM</code> may be empty - the message envelope sender is
	      empty for bounce messages.
	</p></dd><dt><span class="term"><code class="varname">HOME</code></span></dt><dd><p>Home directory of the user running
	      <span class="command"><strong>maildrop</strong></span>.

	</p></dd><dt><span class="term"><code class="varname">HOSTNAME</code></span></dt><dd><p>Network name of the machine running maildrop.
	      Obtained from <span class="citerefentry"><span class="refentrytitle">gethostname</span>(3)</span>.

	</p></dd><dt><span class="term"><code class="varname">LOCKEXT</code></span></dt><dd><p>Extension for dot-lock files (default: <code class="literal">.lock</code>).

	</p></dd><dt><span class="term"><code class="varname">LOCKREFRESH</code></span></dt><dd><p>Refresh interval, in seconds, for dot-locks
	      (default: <code class="literal">15</code>). When <span class="command"><strong>maildrop</strong></span> dot-locks a mailbox, <span class="command"><strong>maildrop</strong></span>
	      tries to refresh the lock periodically in order to keep other programs
	      from removing a stale dot-lock. This is only required if a dot-lock
	      exists for a prolonged period of time, which should be discouraged
	      anyway.

	</p></dd><dt><span class="term"><code class="varname">LOCKSLEEP</code></span></dt><dd><p>Number of seconds to wait to try again to
	      create a dot-lock file, if one already exists (default: 5).

	</p></dd><dt><span class="term"><code class="varname">LOCKTIMEOUT</code></span></dt><dd><p>Number of seconds to wait before removing a
	      stale dot-lock file (default: <code class="literal">60</code>). If a dot-lock file still exists after
	      <code class="varname">LOCKTIMEOUT</code> seconds, <span class="command"><strong>maildrop</strong></span> assumes that the
	      process holding the lock no longer exists, and the dot-lock file can be
	      safely removed. After removing the dot-lock file, <span class="command"><strong>maildrop</strong></span> waits
	      <code class="varname">LOCKSLEEP</code> seconds before trying to create its own dot-lock
	      file, in order to avoid a race condition with another process which is
	      also trying to remove the same stale dot-lock, at the same time.

	</p></dd><dt><span class="term"><code class="varname">LOGNAME</code></span></dt><dd><p>Name of the user to who the message is being
	      delivered.

	</p></dd><dt><span class="term"><code class="varname">MAILDROP_OLD_REGEXP</code></span></dt><dd><p>
	      Revert to using the old legacy pattern matching engine.
	      Versions of <span class="command"><strong>maildrop</strong></span> prior to version 2.0
	      (included in the <span class="application">Courier</span> mail server 0.51,
	      and earlier), used a built-in pattern matching engine, instead of using the
	      <acronym class="acronym">PCRE</acronym>
	      library (see the
	      <span class="quote">“<span class="quote"><a class="link" href="#patterns" shape="rect">Patterns</a></span>”</span>
	      section).
	      <span class="command"><strong>maildrop</strong></span> 1.x used a different syntax for patterns, which
	      is no longer described in this manual page.
	      The old pattern matching engine is still available, by
	      setting <code class="varname">MAILDROP_OLD_REGEXP</code> to <span class="quote">“<span class="quote">1</span>”</span>.
	      Setting this variable will use the legacy pattern matching engine for the
	      rest of the <span class="command"><strong>maildrop</strong></span> recipe file.</p><p>
	      The pattern matching engine will be removed completely in a future version
	      of maildrop.
	      This setting provides for a transitional period of converting old recipes.
	      <code class="varname">MAILDROP_OLD_REGEXP</code> can be set to <span class="quote">“<span class="quote">1</span>”</span> in
	      the global <code class="filename">maildroprc</code> file, then reset to <span class="quote">“<span class="quote">0</span>”</span>
	      in each individual <span class="command"><strong>maildrop</strong></span> recipe file, after it gets
	      converted to the new syntax.</p></dd><dt><span class="term"><code class="varname">MAILFILTER</code></span></dt><dd><p>This is the name of the original <code class="systemitem">filter file</code>
	      that was given to <span class="command"><strong>maildrop</strong></span> on the command line. This is mostly
	      useful to <code class="literal">-default</code> <code class="systemitem">filter file</code>s, it allows them to
	      obtain the <a class="ulink" href="maildrop.html#moption" target="_top" shape="rect">value of the -M option</a>
	      specified on the command line.
	</p></dd><dt><span class="term"><code class="varname">PATH</code></span></dt><dd><p>Command execution path. <span class="command"><strong>maildrop</strong></span> resets PATH
	      to the system default (usually
	      <code class="literal">/bin:/usr/bin:/usr/local/bin</code>).

	</p></dd><dt><span class="term"><code class="varname">SENDMAIL</code></span></dt><dd><p>The mail delivery agent.
	      When <span class="command"><strong>maildrop</strong></span> is
	      instructed to deliver the message to a mailbox whose name begins with the
	      ! character, this is interpreted as a request to forward the message. The
	      <code class="varname">SENDMAIL</code> command is executed to forward the message.

	</p></dd><dt><span class="term"><code class="varname">SHELL</code></span></dt><dd><p>The login shell. The shell is used to execute all
	      commands invoked by <span class="command"><strong>maildrop</strong></span>.

	</p></dd><dt><span class="term"><code class="varname">VERBOSE</code></span></dt><dd><p>Current Debug level (default: <code class="literal">0</code>). Setting <code class="varname">VERBOSE</code> to
	      progressive higher values, between 1 and 9, produces debugging output on
	      standard error. <span class="command"><strong>maildrop</strong></span> ignores
	      the <code class="varname">VERBOSE</code> variable in delivery
	      mode (in order not to confuse the mail transport agent).

	</p></dd><dt><span class="term"><code class="varname">UMASK</code></span></dt><dd><p>The file creation mode mask, in octal.  The
	      default setting of <code class="literal">077</code> creates mailboxes that are readable and writable
	      by the owner only.  Use <code class="literal">007</code> to create mailboxes that are
	      readable/writable by both owner and the group.  Use <code class="literal">037</code>
	      to create
	      mailboxes that are readable by both owner and group, but writable by
	      owner only.  Permissions on existing mailboxes are not changed, this
	      setting affects only new mailboxes.  When delivering to maildirs this
	      setting sets the permissions on new messages only.  Access permissions on
	      messages in maildirs are also affected by the permissions on the maildir
	      directories.
	</p></dd></dl></div></div><div class="refsect2"><a id="idm46044389118688" shape="rect"> </a><h3>Other special variables</h3><p>
	The following variables are automatically used by <span class="command"><strong>maildrop</strong></span> when the
	<code class="systemitem">filter file</code> is being processed:
      </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="varname">EXITCODE</code></span></dt><dd><p>Return code for <span class="command"><strong>maildrop</strong></span>. When
	      <span class="command"><strong>maildrop</strong></span> successfully delivers a message, it terminates with this
	      exit code, which defaults to 0. When the <span class="command"><strong>to</strong></span> or the
	      <span class="command"><strong>cc</strong></span> command is used to deliver the message to an external
	      process, via a pipe, <span class="command"><strong>maildrop</strong></span> will set this variable to the exit
	      code of the external process. Since <span class="command"><strong>maildrop</strong></span> immediately
	      terminates after completing the <span class="command"><strong>to</strong></span> command this means that
	      <span class="command"><strong>maildrop</strong></span>'s exit code will be the exit code of the external
	      process. If the <span class="command"><strong>to</strong></span> command does not deliver the message to a
	      process you must set <code class="varname">EXITCODE</code> before the <span class="command"><strong>to</strong></span>
	      command, since <span class="command"><strong>maildrop</strong></span> terminates immediately after finishing the
	      delivery.

	</p></dd><dt><span class="term"><code class="varname">FLAGS</code></span></dt><dd><p>
	      The <code class="varname">FLAGS</code> variable is used only when delivering
	      a message to a maildir, and may contain only the following
	      letters: <span class="quote">“<span class="quote">D</span>”</span>, <span class="quote">“<span class="quote">F</span>”</span>,
	      <span class="quote">“<span class="quote">R</span>”</span>, and <span class="quote">“<span class="quote">S</span>”</span>. They may appear in
	      any order. When the message gets delivered to the maildir,
	      the message will be marked with a draft, flag, replied, or seen,
	      attribute, correspondingly.
	    </p><p>
	      <code class="varname">FLAGS</code> must be set before the message is
	      delivered to a maildir.
	      The contents of <code class="varname">FLAGS</code> are ignored, when
	      delivering on
	      an mbox folder.
	    </p></dd><dt><span class="term"><code class="varname">KEYWORDS</code></span></dt><dd><p>
	      The <code class="varname">KEYWORDS</code> variable is used only when delivering a
	      message to a maildir, and implements the optional IMAP keyword extension
	      as implemented in the
	      <a class="ulink" href="http://www.courier-mta.org/" target="_top" shape="rect"><span class="application">Courier</span> IMAP server</a>.
	      It may be optionally initialized to contain a comma-separate list of keywords.
	      The <a class="link" href="#to" shape="rect"><span class="command"><strong>to</strong></span></a>, or the
	      <a class="link" href="#cc" shape="rect"><span class="command"><strong>cc</strong></span></a> command, delivers the message
	      to the maildir normally, but also associated the list of keywords in
	      <code class="varname">KEYWORDS</code> with the newly delivered message.</p><p>
	      <code class="varname">KEYWORDS</code> must be set before the message is delivered to
	      a maildir.
	      The contents of <code class="varname">KEYWORDS</code> are ignored, when delivering on
	      an mbox folder.
	</p></dd><dt><span class="term"><code class="varname">LINES</code></span></dt><dd><p>Number of lines in the current message. Note that
	      this may be an approximation. It may or may not take into account the -A
	      option. Use this as criteria for filtering,
	      nothing more.

	</p></dd><dt><span class="term"><code class="varname">MAILDIRQUOTA</code></span></dt><dd><p>Set this variable in order to manually
	      enforce a maximum size on ANY maildir where the message is delivered.
	      This is an optional feature that must be enabled by the system
	      administrator, see <a class="ulink" href="maildirquota.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">maildirquota</span>(8)</span></a> for
	      more information.

	</p></dd><dt><span class="term"><code class="varname">RETURNCODE</code></span></dt><dd><p>This variable is set when <span class="command"><strong>maildrop</strong></span>
	      runs the
	      <a class="ulink" href="#system" target="_top" shape="rect">system</a> command,
	      <a class="ulink" href="#xfilter" target="_top" shape="rect">xfilter</a> command, or a command that's
	      specified within a pair of backtick characters ( command substitution ).
	      The <code class="varname">RETURNCODE</code> variable will be set to the exit code of the
	      command, after it completes.

	</p></dd><dt><span class="term"><code class="varname">SIZE</code></span></dt><dd><p>Number of bytes in the message. This may or may not
	      include the -A option. Use this as a criteria
	      for filtering, nothing more.</p></dd></dl></div></div><div class="refsect2"><a id="idm46044389086400" shape="rect"> </a><h3>Unquoted text</h3><p>
	All text strings in <code class="systemitem">filter file</code>s should be in single, or double quotes.
	However, for convenience sake, quotes can be omitted under certain
	circumstances.</p><p>
	Text that includes ONLY letters, digits, and the following characters:
	<code class="literal">_-.:/${}@</code> may appear without quotes. Note that this does not
	allow spaces, or backslashes to be entered, however the text is still
	variable-substituted, and the substituted text may contain other
	characters.</p><p>
	Also, note that patterns (see below) begin with the slash character.
	Normally, anything that begins with the slash is interpreted as a pattern.
	However, text immediately after <span class="quote">“<span class="quote">VARIABLE=</span>”</span> is interpreted as a
	string even if it begins with a slash. This is why something like:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
MAILDIR=/var/mail
	  </pre></div></blockquote></div><p>
	works as expected. Using quotes, though, is highly recommended. You must use
	quotes to set a variable to a lone slash, because an unquoted slash is
	interpreted as a division sign.</p><p>
	Long double or singly-quoted text can be broken across multiple lines by
	ending the line with a lone backslash character, like this:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
TEXT="This is a long \
   text string"
	  </pre></div></blockquote></div><p>
	The backslash, the newline, and all leading whitespace on the next line is
	removed, resulting in "This is a long text string".</p></div><div class="refsect2"><a id="idm46044389077424" shape="rect"> </a><h3>Command substitution</h3><p>
	Text enclosed in back-tick characters is interpreted as a shell command. The
	shell command is executed as a child process by <span class="command"><strong>maildrop</strong></span>.
	Its output is used in place of the command. For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
DIR=`ls`
	  </pre></div></blockquote></div><p>
	places the names of the files in the current directory into the DIR
	variable.</p><p>
	The output of the command will have all newline characters replaced by
	spaces, and leading and trailing spaces will be stripped (multiple spaces are
	not removed, though). Also, the contents of the message being delivered is
	made available to the command on standard input.</p></div><div class="refsect2"><a id="idm46044389072880" shape="rect"> </a><h3>Patterns</h3><a id="patterns" shape="rect"> </a><p>
	The pattern syntax in <span class="command"><strong>maildrop</strong></span> is similar to the
	<span class="command"><strong>grep</strong></span> command's syntax, with some minor differences.
	A pattern takes the following
	form in the <code class="systemitem">filter file</code>:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
/<em class="replaceable"><code>pattern</code></em>/:<em class="replaceable"><code>options</code></em>
	  </pre></div></blockquote></div><p>
	<em class="replaceable"><code>pattern</code></em> specifies the text to look for in the
	message, in the <code class="literal">UTF-8</code> codeset.
	<em class="replaceable"><code>pattern</code></em> must not begin with a space,
	otherwise the leading slash will then be
	interpreted as a division sign. If you must search for text that starts
	with a space, use something like <code class="literal">"/[ ] ... /"</code>.
      </p><p>
	The general syntax of <span class="command"><strong>maildrop</strong></span>'s patterns is
	described in the <span class="citerefentry"><span class="refentrytitle">pcrepattern</span>(3)</span>
	manual page, with certain exceptions
	noted below.
	<span class="command"><strong>maildrop</strong></span> uses the
	<a class="ulink" href="http://www.pcre.org" target="_top" shape="rect">PCRE</a>
	library to implement pattern matching.
	Not all features in <acronym class="acronym">PCRE</acronym> are available in
	<span class="command"><strong>maildrop</strong></span>, and
	the <span class="quote">“<span class="quote">options</span>”</span> part, which follows the pattern
	specification, changes the pattern matching further.
	Consult the
	<span class="citerefentry"><span class="refentrytitle">pcrepattern</span>(3)</span>
	manual page for more information, but note the following
	exceptions:
      </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
	    Internal options settings are not supported (but see the
	    <span class="quote">“<span class="quote">D</span>”</span> maildrop option, below).
	    Do not include option settings in the
	    <em class="replaceable"><code>pattern</code></em>,
	    doing so will lead to undefined results.</p></li><li class="listitem"><p>
	    Named subpatterns are not implemented.
	    Numbered subpatterns are implemented, see
	    <span class="quote">“<span class="quote"><a class="link" href="#patmatch" shape="rect">Pattern Match Results</a></span>”</span>,
	    below.
	  </p></li><li class="listitem"><p>
	    The search pattern gets executed not against the raw message text,
	    but the message transcoded into a canonical UTF-8-based format.
	    This process involves transcoding any non-UTF-8 message content
	    into UTF-8. Additionally, message headers get converted into a
	    canonical format before the search pattern gets executed.
	  </p><p>
	    For structured headers with email addresses, the process involves
	    removing extraneous punctuation, or adding missing ones (in
	    situations where a missing punctuation character can be deduced).
	    Additionally certain pre-RFC822 obsolete header formats get
	    converted to canonical form.
	  </p><p>
	    This means that header search patterns that include punctuation
	    character may appear not to work against obviously-matching
	    message text. Use <span class="quote">“<span class="quote">reformime -u &lt;message.txt</span>”</span>,
	    with <code class="filename">message.txt</code> containing the sample message,
	    to see exactly the actual text that gets searched by patterns.
	  </p></li></ul></div></div><div class="refsect2"><a id="idm46044389051264" shape="rect"> </a><h3>Pattern options</h3><a id="options" shape="rect"> </a><p>
	Following <code class="literal">/<em class="replaceable"><code>pattern</code></em>/,</code>
	there may be an optional colon, followed by one. or
	more options. The following options may be specified in any order:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">h</code></span></dt><dd><p>
	      Match this pattern in the message's header, and the
	      header of any attachments in the message.
	    </p></dd><dt><span class="term"><code class="literal">H</code></span></dt><dd><p>
	      Match this pattern in the message's main header. Do not match
	      this pattern in the headers of the message's attachments.
	    </p></dd><dt><span class="term"><code class="literal">b</code></span></dt><dd><p>Match this pattern against the message body.</p></dd><dt><span class="term"><code class="literal">D</code></span></dt><dd><p>This is a case sensitive match. Normally the patterns match either
	      uppercase or lowercase text. <code class="literal">/john/</code> will match "John",
	      "john", or "JOHN". Specify the D option for a case-sensitive search:
	      lowercase letters in the pattern must match lowercase letters in the
	      message; ditto for uppercase.</p></dd></dl></div><p>
	If neither 'h', 'H', or 'b' is specified, 'h' is the default,
	matching the pattern in the message's header, and all attachments'
	headers. Specifying the 'b' option causes the pattern to be matched
	against the message body.
	Specifying 'b' and 'h' causes the pattern to be matched
	against the entire message.
      </p><p>
	Normally, each line in the message gets matched against the pattern
	individually. When applying patterns to a header, multi-line headers (headers
	split on several lines by beginning each continuation line with whitespace)
	are silently combined into a single line, before the pattern is applied.</p></div><div class="refsect2"><a id="idm46044389038304" shape="rect"> </a><h3>MIME encoding</h3><p>
	The pattern must be a valid text string in the <code class="literal">UTF-8</code>
	codeset, and <span class="command"><strong>maildrop</strong></span> should handle messages
	that use MIME encodings in other known character sets.
	<a class="link" href="#options" shape="rect">Options</a> that specify a
	message header search
	result in <span class="command"><strong>maildrop</strong></span> searching the initial message
	headers, and any headers of additional MIME sections, in a multipart
	MIME message. Options that specify a message body search will search
	through all "text" MIME content.
      </p><p>
	For a MIME search to succeed, the message must be a well-formed MIME
	message (with a Mime-Version: 1.0 header).
      </p></div><div class="refsect2"><a id="idm46044389033808" shape="rect"> </a><h3>Weighted scoring</h3><p>
	Patterns are evaluated by <span class="command"><strong>maildrop</strong></span> as any other numerical
	expression. If a pattern is found, <span class="command"><strong>maildrop</strong></span>'s filter
	interprets the
	results of the pattern match as number 1, or true, for filtering purposes. If
	a pattern is not found the results of the pattern search is zero. Once a
	pattern is found, the search stops. Second, and subsequent occurrences of the
	same pattern are NOT searched for.</p><p>
	<span class="command"><strong>maildrop</strong></span> can also do weighted scoring. In weighted scoring,
	multiple occurrences of the same pattern are used to calculate a numerical
	score.</p><p>
	To use a weighted search, specify the pattern as follows:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
/<em class="replaceable"><code>pattern</code></em>/:<em class="replaceable"><code>options</code></em>,<em class="replaceable"><code>xxx</code></em>,<em class="replaceable"><code>yyy</code></em>
	  </pre></div></blockquote></div><p>
	where <em class="replaceable"><code>xxx</code></em> and <em class="replaceable"><code>yyy</code></em> are
	two numbers. <em class="replaceable"><code>yyy</code></em> is optional -- it will
	default to 1, if missing.</p><p>The first occurrence of the pattern is evaluated as xxx. The second
	occurrence of the pattern is evaluated as xxx*yyy, the third as xxx*yyy*yyy,
	etc... All occurrences of the pattern are added up to calculate the final
	score.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	  <span class="command"><strong>maildrop</strong></span> does not
	  recognize multiple occurrences of the same pattern in the same line.
	  Multiple occurences of the same pattern in one line count as one
	  occurence.</p></div></div><div class="refsect2"><a id="idm46044389023296" shape="rect"> </a><h3>Pattern Match Results</h3><a id="patmatch" shape="rect"> </a><p>
	After a pattern is successfully matched, the actual text that is matched
	is placed in the <code class="varname">MATCH</code> variable. For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
/^From:.*/
	  </pre></div></blockquote></div><p>
	matches a line of the form:
      </p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
From: postmaster@localhost
	  </pre></div></blockquote></div><p>
	Here the variable <code class="varname">MATCH</code> will be set to "From:
	postmaster@localhost", which can be used in subsequent statements.</p><p>
	If the pattern contains subpatterns, the portions of the text that match
	the first subpattern is placed in the <code class="varname">MATCH1</code> variable.
	The second subpattern, if any, is placed in <code class="varname">MATCH2</code>, and
	so on:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
/^From:\s+(.*)@(.*)/
	  </pre></div></blockquote></div><p>
	matched against the same line will set <code class="varname">MATCH</code> to
	<span class="quote">“<span class="quote">From: postmaster@localhost</span>”</span>,
	<code class="varname">MATCH1</code> to <span class="quote">“<span class="quote">postmaster</span>”</span>, and
	<code class="varname">MATCH2</code> to <span class="quote">“<span class="quote">localhost</span>”</span>.
	Of course, in real world the <span class="quote">“<span class="quote">From:</span>”</span> header is usually much
	more complicated, and can't be handled that easily.
	This is just an illustrative example.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	  Subpatterns are not processed in the <code class="literal">foreach</code>
	  statement.</p></div></div><div class="refsect2"><a id="conversion" shape="rect"> </a><h3>Conversion of <span class="command"><strong>maildrop</strong></span> 1.x patterns to 2.0</h3><p>
	Although the new <acronym class="acronym">PCRE</acronym>-based pattern matching code in
	<span class="command"><strong>maildrop</strong></span> is completely different from the built-in
	pattern matching code in <span class="command"><strong>maildrop</strong></span> 1.x, very few changes
	will be required to convert recipes to the new syntax.
	The only major differences are:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
	    The subexpression format has changed.
	    Any pattern that uses subexpression needs to be converted.
	    Additionally, references to <code class="varname">MATCH2</code> must be replaced
	    with <code class="varname">MATCH1</code>, <code class="varname">MATCH3</code> to
	    <code class="varname">MATCH2</code>, and so on.
	    References to plain old <code class="varname">MATCH</code> will remain the
	    same.</p></li><li class="listitem"><p>
	    The <span class="quote">“<span class="quote">w</span>”</span> pattern option is no longer possible, with
	    <acronym class="acronym">PCRE</acronym>.
	    The very few recipes that use this option, if any actually exist,
	    will have to be rewritten in some other fashion.</p></li></ul></div></div><div class="refsect2"><a id="idm46044389000992" shape="rect"> </a><h3>Expressions</h3><p>
	Although <span class="command"><strong>maildrop</strong></span> evaluates expressions numerically,
	results of
	expressions are stored as text literals. When necessary, text literals are
	converted to numbers, then the results of a mathematical operation is
	converted back into a text literal.</p><div class="refsect3"><a id="idm46044388999344" shape="rect"> </a><h4>Operators</h4><p>
	  The following operators carry their usual meaning, and are listed in order
	  from lowest precedence, to the highest:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">

||
&amp;&amp;
&lt;  &lt;=  &gt;  &gt;=  ==  !=  lt  le  gt  ge  eq  ne
|
&amp;
+  -
*  /
=~ /<em class="replaceable"><code>pattern</code></em>/
/<em class="replaceable"><code>pattern</code></em>/  !  ~  <em class="replaceable"><code>function()</code></em>
	    </pre></div></blockquote></div></div><div class="refsect3"><a id="idm46044388995344" shape="rect"> </a><h4>Variable assignment</h4><a id="assign" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
VARIABLE=<em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  Assigns the result of the expression to <em class="replaceable"><code>VARIABLE</code></em>
	  (note no leading $ in front of variable).
	</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    If <em class="replaceable"><code>VARIABLE</code></em> is NOT surrounded by quotes, then it
	    may contain only letters, numbers, underscores, dashes, and a selected few
	    other characters. In order to initialize a variable whose name contains
	    non-standard punctuation marks, surround the name of the variable with
	    quotes.</p></div></div><div class="refsect3"><a id="idm46044388990080" shape="rect"> </a><h4>cc - deliver a copy of the message</h4><a id="cc" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
cc <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  The <span class="command"><strong>cc</strong></span> statement is very similar to the
	  <span class="command"><strong>to</strong></span> statement, except
	  that after delivering the message <span class="command"><strong>maildrop</strong></span> continues
	  to process the
	  <code class="systemitem">filter file</code>,
	  unlike the <span class="command"><strong>to</strong></span> statement which immediately
	  terminates <span class="command"><strong>maildrop</strong></span> after the delivery is complete.
	  Essentially, the
	  message is carbon copied to the given mailbox, and may be delivered again to
	  another mailbox by another <span class="command"><strong>cc</strong></span> or
	  <span class="command"><strong>to</strong></span> statement.</p><p>
	  <a class="ulink" href="#to" target="_top" shape="rect">See the <span class="command"><strong>to</strong></span> statement</a> for more
	  details.
	  When
	  <span class="command"><strong>cc</strong></span> is used to deliver a message to a process
	  <span class="command"><strong>maildrop</strong></span>
	  will set the <code class="varname">EXITCODE</code> variable to the process's exit
	  code.</p></div><div class="refsect3"><a id="idm46044388977904" shape="rect"> </a><h4>dotlock - create a manual dot-lock</h4><a id="dotlock" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
dotlock <em class="replaceable"><code>expression</code></em> {

   ...

}
	    </pre></div></blockquote></div><p>
	  <span class="command"><strong>maildrop</strong></span> automatically creates a lock when a message is
	  delivered to a
	  mailbox. Depending upon your system configuration,
	  <span class="command"><strong>maildrop</strong></span> will use
	  either dot-locks, or the flock() system call.</p><p>The <span class="command"><strong>dotlock</strong></span> statement creates an explicit dot-lock
	  file. Use the <a class="ulink" href="#flock" target="_top" shape="rect"><span class="command"><strong>flock</strong></span> statement</a> to create an
	  explicit flock()
	  lock.</p><p>The <em class="replaceable"><code>expression</code></em> is a filename that should be
	  used as a lock file.
	  <span class="command"><strong>maildrop</strong></span> creates the indicated dot-lock, executes the
	  filtering
	  instructions contained within the { ... } block, and removes the lock. The
	  expression <span class="emphasis"><em>must</em></span> be the name of the dot-lock file itself,
	  <span class="emphasis"><em>NOT</em></span>
	  the name of the mailbox file you want to lock.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    With manual locking, it is possible to deadlock multiple
	    <span class="command"><strong>maildrop</strong></span> processes (or any other processes that try to
	    claim the same
	    locks).</p><p>No deadlock detection is possible with dot-locks, and since
	    <span class="command"><strong>maildrop</strong></span> automatically refreshes all of its dot-locks
	    regularly, they
	    will never go stale. You'll have <span class="command"><strong>maildrop</strong></span> processes
	    hanging in limbo,
	    until their watchdog timers go off, aborting the mail delivery.</p></div></div><div class="refsect3"><a id="idm46044388964880" shape="rect"> </a><h4>echo - output diagnostic information</h4><a id="echo" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
echo <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  <span class="command"><strong>maildrop</strong></span> will print the given text. This is usually used
	  when
	  <span class="command"><strong>maildrop</strong></span> runs in embedded mode, but can be used for
	  debugging
	  purposes. Normally, a newline is printed after the text. If text is
	  terminated with a \c, no newline will be printed.</p></div><div class="refsect3"><a id="idm46044388959936" shape="rect"> </a><h4>exception - trap fatal errors</h4><a id="exception" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
exception {

   ...

}
	    </pre></div></blockquote></div><p>
	  The <span class="command"><strong>exception</strong></span> statement traps errors that would normally
	  cause
	  <span class="command"><strong>maildrop</strong></span> to terminate. If a fatal error is encountered
	  anywhere within the
	  block of statements enclosed by the <span class="command"><strong>exception</strong></span> clause,
	  execution will
	  resume immediately following the <span class="command"><strong>exception</strong></span> clause.</p></div><div class="refsect3"><a id="idm46044388954112" shape="rect"> </a><h4>exit - terminate filtering unconditionally</h4><a id="exit" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
exit
	    </pre></div></blockquote></div><p>
	  The <span class="command"><strong>exit</strong></span> statement immediately terminates filtering.
	  <span class="command"><strong>maildrop</strong></span>'s
	  return code is set to the value of the <code class="varname">EXITCODE</code> variable.
	  Normally, <span class="command"><strong>maildrop</strong></span> terminates immediately after <a class="ulink" href="#to" target="_top" shape="rect">successfully delivering the message</a> to a mailbox. The
	  <span class="command"><strong>exit</strong></span> statement causes <span class="command"><strong>maildrop</strong></span> to
	  terminate without delivering the message anywhere.</p><p>The <span class="command"><strong>exit</strong></span> statement is usually used when
	  <span class="command"><strong>maildrop</strong></span> runs in <a class="ulink" href="maildrop.html#embedded" target="_top" shape="rect">embedded mode</a>, when message
	  delivery instructions are not allowed.</p></div><div class="refsect3"><a id="idm46044388944528" shape="rect"> </a><h4>flock - create an manual flock() lock</h4><a id="flock" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
flock <em class="replaceable"><code>expression</code></em> {

   ...

}
	    </pre></div></blockquote></div><p>
	  <span class="command"><strong>maildrop</strong></span> automatically creates a lock when a message is delivered to a
	  mailbox. Depending upon your system configuration, <span class="command"><strong>maildrop</strong></span> will use
	  either dot-locks, or the flock() system call.</p><p>The <span class="command"><strong>flock</strong></span> statement creates a manual flock() lock.
	  Use the <a class="ulink" href="#dotlock" target="_top" shape="rect"><span class="command"><strong>dotlock</strong></span> statement</a>
	  to create a manual dot-lock
	  file.</p><p>The <em class="replaceable"><code>expression</code></em> is the name of the
	  file that should be locked.
	  <span class="command"><strong>maildrop</strong></span> creates the lock on the indicated file, executes
	  the
	  filtering instructions contained within the { ... } block, and removes the
	  lock.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    With manual locking, it is possible to deadlock multiple
	    <span class="command"><strong>maildrop</strong></span> processes (or any other
	    processes that try to claim the same
	    locks). The operating system will automatically break flock() deadlocks. When
	    that happens, one of the <span class="command"><strong>maildrop</strong></span> processes will terminate
	    immediately. Use the <span class="command"><strong>exception</strong></span> statement in order to trap
	    this
	    exception condition, and execute an alternative set of filtering
	    instructions.</p></div></div><div class="refsect3"><a id="idm46044388932912" shape="rect"> </a><h4>foreach - iterate over text sections matched by a pattern</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
foreach /pattern/:options
{
   ...
}

foreach (expression) =~ /pattern/:options
{
   ...
}
	    </pre></div></blockquote></div><p>
	  The <span class="command"><strong>foreach</strong></span> statement executes a block of statements for
	  each
	  occurrence of the given pattern in the given message, or expression. On every
	  iteration <code class="varname">MATCH</code> variable will be set to the matched string.
	  All the usual options may be applied to the pattern match,
	  EXCEPT the following:
	  </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">,xxx,yyy</span></dt><dd><p>
		  Weighted scoring is meaningless, in this context.</p></dd><dt><span class="term">( ... )</span></dt><dd><p>
		  Subpatterns are not processed.
		  Only the <code class="varname">MATCH</code> variable will be set for each found
		  pattern.</p></dd></dl></div><p>
	</p></div><div class="refsect3"><a id="idm46044388925024" shape="rect"> </a><h4>if - conditional execution</h4><a id="if" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
else
{
   ...
}
	    </pre></div></blockquote></div><p>
	  Conditional execution. If <em class="replaceable"><code>expression</code></em>
	  evaluates to a logical true (note -
	  parenthesis are required) then the first set of statements is executed.
	  The <span class="command"><strong>else</strong></span> keyword, and the subsequent statements, are
	  optional. If present,
	  and the expression evaluates to a logical false, the
	  <span class="command"><strong>else</strong></span> part is executed.</p><p>
	  <span class="command"><strong>maildrop</strong></span> evaluates all expression as text strings.
	  In the context
	  of a logical expression, an empty string, or the number 0 constitutes a
	  logical false value, anything else is a logical true value.</p><p>If the <span class="command"><strong>if</strong></span> part, or the
	  <span class="command"><strong>else</strong></span>
	  part consists of only one
	  statement, the braces may be omitted.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    The grammar of this <span class="command"><strong>if</strong></span> statement is stricter than
	    usual.
	    If
	    you get baffling syntax errors from <span class="command"><strong>maildrop</strong></span>, make sure that the
	    braces, and the if statement, appear on separate lines. Specifically: the
	    closing parenthesis, the closing braces, and the else statement, must be at
	    the end of the line (comments are allowed), and there may not be any blank
	    lines in between (not even ones containing comments only).</p></div><p>
	  If the <span class="command"><strong>else</strong></span> part contains a single <span class="command"><strong>if</strong></span>,
	  and nothing else,
	  this may be combined into an <span class="command"><strong>elsif</strong></span>:
	</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
elsif (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
	    </pre></div></blockquote></div><p>
	  The above example is logically identical to:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
else
{
   if (<em class="replaceable"><code>expression</code></em>)
   {
      ...
   }
}
	    </pre></div></blockquote></div><p>
	  Consecutive <span class="command"><strong>elsif</strong></span> sequences are allowed:
	</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
elsif (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
elsif (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
	    </pre></div></blockquote></div><p>
	  Consecutive occurences of <span class="command"><strong>elsif</strong></span> commands eliminate a
	  significant amount of indentation, and the resulting code is more readable.
	</p></div><div class="refsect3"><a id="idm46044388902864" shape="rect"> </a><h4>import - access original environment variable</h4><a id="import" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
import <em class="replaceable"><code>variable</code></em>
	    </pre></div></blockquote></div><p>When <span class="command"><strong>maildrop</strong></span> starts,
	  it normally imports the contents of the
	  environment variables, and assigns them to internal <span class="command"><strong>maildrop</strong></span>
	  variables. For example, if there was an environment variable
	  <code class="varname">FOO</code>, the internal <span class="command"><strong>maildrop</strong></span> variable
	  <code class="varname">FOO</code> will
	  have the contents of the environment variable.
	  From then on, <code class="varname">FOO</code>
	  will be no different than any other variable,
	  and when <span class="command"><strong>maildrop</strong></span> runs
	  an external command, the contents of <span class="command"><strong>maildrop</strong></span>'s
	  variables will be
	  exported as the environment for the command.</p><p>Certain variables, like <code class="varname">HOME</code> and
	  <code class="varname">PATH</code>, are always reset to fixed defaults,
	  for security reasons.
	  Also, in delivery and embedded modes, the environment is not imported at all
	  (with the exception of system locale environment variables),
	  and <span class="command"><strong>maildrop</strong></span> starts with only the fixed default
	  variables.</p><p>
	  The <span class="command"><strong>import</strong></span> statement initializes the specified
	  variable with the contents of the original environment variable
	  when <span class="command"><strong>maildrop</strong></span> started.  For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
echo "PATH is $PATH"
PATH="/bin"
echo "PATH is $PATH"
import PATH
echo "PATH is $PATH"
exit
	    </pre></div></blockquote></div><p>This results in the following output:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
PATH is /bin:/usr/bin:/usr/local/bin
PATH is /bin
PATH is /home/root/bin:/sbin:/usr/sbin:/bin:/usr/bin:/usr/local/bin
	    </pre></div></blockquote></div><p>
	  This shows that when <span class="command"><strong>maildrop</strong></span> starts
	  <code class="varname">PATH</code> is set to the fixed default of
	  <code class="literal">/bin:/usr/bin:/usr/local/bin</code>.
	  However, the original contents of
	  the <code class="varname">PATH</code> environment variable we different, and the
	  <span class="command"><strong>import</strong></span> statement shows what it was.</p></div><div class="refsect3"><a id="idm46044388884496" shape="rect"> </a><h4>include - execute filtering instructions from another file</h4><a id="include" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
include <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  The include statement reads a file, and executes filtering instructions
	  contained in that file. Note that the include statement is processed when the
	  current <code class="systemitem">filter file</code> is being executed. When <span class="command"><strong>maildrop</strong></span> reads the initial
	  <code class="systemitem">filter file</code>, any syntax errors in the filtering instructions are immediately
	  reported, and <span class="command"><strong>maildrop</strong></span> will terminate with a return code of
	  <span class="errorcode">EX_TEMPFAIL</span>. Any errors in files specified by
	  <span class="command"><strong>include</strong></span>
	  statements are NOT reported, because those files will not be read until the
	  <span class="command"><strong>include</strong></span> statement is itself executed.</p><p>
	  If the specified file does not exist, or if there are any syntax errors in
	  the file, <span class="command"><strong>maildrop</strong></span> reports the error, and terminates with
	  a return
	  code of <span class="errorcode">EX_TEMPFAIL</span>.</p></div><div class="refsect3"><a id="idm46044388873936" shape="rect"> </a><h4>log, logfile - log message deliveries</h4><a id="log" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
logfile <em class="replaceable"><code>expression</code></em>

log <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  Logging in <span class="command"><strong>maildrop</strong></span> is normally turned off.
	  The <span class="command"><strong>logfile</strong></span>
	  statement specifies the file where
	  <span class="command"><strong>maildrop</strong></span> will log how the message has been
	  disposed of. The parameter is then name of the file. If the
	  file exists <span class="command"><strong>maildrop</strong></span> appends to the file.</p><p>
	  For each delivery (the <a class="ulink" href="#to" target="_top" shape="rect"><span class="command"><strong>to</strong></span></a>
	  and <a class="ulink" href="#cc" target="_top" shape="rect"><span class="command"><strong>cc</strong></span></a>
	  statements, and default deliveries)
	  <span class="command"><strong>maildrop</strong></span> records the
	  <code class="literal">From:</code> and the
	  <code class="literal">Subject:</code> fields, together with
	  the current time, in the log file.</p><p>
	  The <span class="command"><strong>log</strong></span> statement adds additional logging text to the
	  log file. The <span class="command"><strong>log</strong></span> statement works exactly like
	  the <span class="command"><strong>echo</strong></span>
	  statement, except that the text is written to the logfile, instead of
	  standard output.</p></div><div class="refsect3"><a id="idm46044388860736" shape="rect"> </a><h4>system - execute a system command</h4><a id="system" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
system <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  <em class="replaceable"><code>expression</code></em> specifies an external program
	  that
	  <span class="command"><strong>maildrop</strong></span> runs as a subprocess.
	  The subprocess's standard input gets connected to
	  <code class="filename">/dev/null</code>, and the subprocess inherits
	  the standard output and error from
	   <span class="command"><strong>maildrop</strong></span>.</p></div><div class="refsect3"><a id="idm46044388854864" shape="rect"> </a><h4>to - deliver message to a mailbox</h4><a id="to" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
to <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  The <span class="command"><strong>to</strong></span> statement delivers the message to a mailbox.
	  <em class="replaceable"><code>expression</code></em>
	  must evaluate to a valid mailbox. A valid mailbox is either a mailbox file, a
	  maildir, or an external program (which includes forwarding to another
	  address).</p><p>
	  The <span class="command"><strong>to</strong></span> statement is the final delivery statement.
	  <span class="command"><strong>maildrop</strong></span>
	  delivers message, then immediately terminates,
	  with its return code set to
	  the <code class="varname">EXITCODE</code> variable.
	  If there was an error while
	  delivering the message, <span class="command"><strong>maildrop</strong></span> terminates with the
	  <span class="errorcode">EX_TEMPFAIL</span> exit code. A properly-written mail
	  transport agent
	  should re-queue the message, and re-attempt delivery at some later time.</p><p>
	  An <em class="replaceable"><code>expression</code></em> that begins with the
	  "<span class="token">|</span>" character
	  specifies an external program to run to handle the actual
	  delivery. The <code class="varname">SHELL</code> variable specifies the shell to
	  execute the
	  given command. The message is provided to the command on standard input.
	  <span class="command"><strong>maildrop</strong></span>'s exit code will be the process's exit
	  code.</p><p>
	  An <em class="replaceable"><code>expression</code></em> that begins
	  with an exclamation mark, "<span class="token">!</span>"
	  specifies a whitespace-delimited
	  list of E-mail addresses to forward the message
	  to.
	  The program
	  specified by the <code class="varname">SENDMAIL</code> variable is run as an
	  external program, with the list of E-mail addresses provided as parameters to
	  the program.</p><p>
	  Otherwise, <em class="replaceable"><code>expression</code></em> names the mailbox
	  where <span class="command"><strong>maildrop</strong></span> delivers the message.
	  If <em class="replaceable"><code>expression</code></em> is a directory,
	  <span class="command"><strong>maildrop</strong></span> assumes
	  that the directory is a maildir directory.
	  Otherwise, <span class="command"><strong>maildrop</strong></span> will deliver
	  the message to a file, formatted in traditional mailbox format.
	  <span class="command"><strong>maildrop</strong></span> will use either dot-locking, or flock()-locking
	  when
	  delivering the message to the file.</p></div><div class="refsect3"><a id="idm46044388838496" shape="rect"> </a><h4>while - repeatedly execute a block of statements</h4><a id="while" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
while (<em class="replaceable"><code>expression</code></em>)
{
   ...
}
	    </pre></div></blockquote></div><p>
	  The <em class="replaceable"><code>expression</code></em> is repeatedly evaluated.
	  Each time it <a class="ulink" href="#if" target="_top" shape="rect">evaluates to a logical true</a>,
	  the statements inside the braces
	  are executed.
	  When <em class="replaceable"><code>expression</code></em> evaluates to a logical false,
	  the while loop is over. Take care to avoid infinite loops.</p></div><div class="refsect3"><a id="idm46044388833488" shape="rect"> </a><h4>xfilter - filter message through another program</h4><a id="xfilter" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
xfilter <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  <em class="replaceable"><code>expression</code></em> specifies an external program that
	  <span class="command"><strong>maildrop</strong></span> runs to filter the current message.
	  The current
	  message will be piped to the filter program as standard input. The output of
	  the filter program replaces the current message being delivered. The external
	  program must terminate with an exit code of 0. If the external program does
	  not terminate with an exit code of 0, or if it does not read the message from
	  the standard input, <span class="command"><strong>maildrop</strong></span> terminates with an exit code of
	  <span class="errorcode">EX_TEMPFAIL</span>.</p></div><div class="refsect3"><a id="idm46044388827808" shape="rect"> </a><h4>|| - logical or</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">||</span> <em class="replaceable"><code>expression2</code></em>

	    </pre></div></blockquote></div><p>
	  If <em class="replaceable"><code>expression1</code></em> evaluates to a logical true,
	  the result of the <span class="token">||</span> is
	  <em class="replaceable"><code>expression1</code></em>, otherwise it's
	  <em class="replaceable"><code>expression2</code></em>, which is evaluated.</p><p>
	  <span class="command"><strong>maildrop</strong></span> uses the following concept of true/false:
	  an empty text
	  literal, or a text literal that consists of the single character "0" is a
	  logical false value. Anything else is a logical true value.</p></div><div class="refsect3"><a id="idm46044388821568" shape="rect"> </a><h4>&amp;&amp; - logical and</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">&amp;&amp;</span> <em class="replaceable"><code>expression2</code></em>

	    </pre></div></blockquote></div><p>
	  If <em class="replaceable"><code>expression1</code></em> evaluates to a logical false,
	  the result of the <span class="token">&amp;&amp;</span> is
	  <em class="replaceable"><code>expression1</code></em>, otherwise it's
	  <em class="replaceable"><code>expression2</code></em>, which is evaluated.</p><p>
	  <span class="command"><strong>maildrop</strong></span> uses the following concept of true/false:
	  an empty text
	  literal, or a text literal that consists of the single character "0" is a
	  logical false value. Anything else is a logical true value.</p></div><div class="refsect3"><a id="idm46044388815120" shape="rect"> </a><h4>&lt;, &lt;=, &gt;, &gt;=, ==, !=   - numerical comparison</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">&lt;</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">&lt;=</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">&gt;</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">&gt;=</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">==</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">!=</span> <em class="replaceable"><code>expression2</code></em>

	    </pre></div></blockquote></div><p>
	  These operators compare their left hand side expression against their right
	  hand side. These operators compare the numerical values of each side, as
	  floating point numbers. If the numbers compare as indicated, the result of
	  the comparison is the text string "1", otherwise it is the text
	  string 0.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Ccomparisons are not associative:
	    "<code class="literal">a &lt; b &lt; c</code>" is an error.
	    If it is absolutely necessary, use
	    "<code class="literal">(a &lt; b) &lt; c</code>".</p></div></div><div class="refsect3"><a id="idm46044388803120" shape="rect"> </a><h4>lt, le, gt, ge, eq, ne - text comparison</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">lt</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">le</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">gt</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">ge</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">eq</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">ne</span> <em class="replaceable"><code>expression2</code></em>

	    </pre></div></blockquote></div><p>
	  These operators compare their left hand side expression against their right
	  hand side. These operators compare each side as text strings (alphabetically,
	  although the text may include anything). If the text strings compare as
	  indicated, the result of the comparison is the text string "1", otherwise it
	  is the text string 0.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    Comparisons are not associative: "<code class="literal">a lt b lt c</code>"
	    is an error. If it is
	    absolutely necessary, use "<code class="literal">(a lt b) lt c</code>".
	    (But why would you?).</p></div></div><div class="refsect3"><a id="idm46044388791568" shape="rect"> </a><h4>| - bitwise or</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">|</span> <em class="replaceable"><code>expression2</code></em>
	    </pre></div></blockquote></div><p>
	  This is the bitwise or operator. Its result is a 32 bit
	  integer, which is a bitwise-or combination of the left hand side and the
	  right hand side.</p></div><div class="refsect3"><a id="idm46044388787696" shape="rect"> </a><h4>&amp; - bitwise and</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">&amp;</span> <em class="replaceable"><code>expression2</code></em>
	    </pre></div></blockquote></div><p>
	  This is the bitwise and operator. Its result is a 32 bit
	  integer, which is a bitwise-and combination of the left hand side and the
	  right hand side.</p></div><div class="refsect3"><a id="idm46044388783824" shape="rect"> </a><h4>+, -, *, / - numerical operations</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression1</code></em> <span class="token">+</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">-</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">*</span> <em class="replaceable"><code>expression2</code></em>

<em class="replaceable"><code>expression1</code></em> <span class="token">/</span> <em class="replaceable"><code>expression2</code></em>

	    </pre></div></blockquote></div><p>
	  These are numerical, floating point, operators.</p></div><div class="refsect3"><a id="idm46044388776672" shape="rect"> </a><h4>=~ /pattern/:options - pattern match against string</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<em class="replaceable"><code>expression</code></em> <span class="token">=~</span> /<em class="replaceable"><code>pattern</code></em>/:<em class="replaceable"><code>option</code></em>
	    </pre></div></blockquote></div><p>
	  The left hand side of the <span class="token">=~</span> operator can be any expression.
	  The right hand
	  side is always a pattern specification. The result of the operator is the
	  weighted match of the pattern against
	  <em class="replaceable"><code>expression</code></em> (if the options do not
	  specify weighted scoring, the result is simply 1 if the pattern was found,
	  0 if not).</p><p>
	  See "<a class="ulink" href="#patterns" target="_top" shape="rect">Patterns</a>" for more information.</p></div><div class="refsect3"><a id="idm46044388770496" shape="rect"> </a><h4>/pattern/:options - pattern match against message</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
/<em class="replaceable"><code>pattern</code></em>/:<em class="replaceable"><code>option</code></em>
	    </pre></div></blockquote></div><p>
	  The result of this operator is the weighted match of the pattern against the
	  current message (if the options do not specify weighted scoring, the result
	  is simply 1 if the pattern was found, 0 if not).</p><p>
	  See "<a class="ulink" href="#patterns" target="_top" shape="rect">Patterns</a>" for more information.</p></div><div class="refsect3"><a id="idm46044388765952" shape="rect"> </a><h4>!, ~ - logical/bitwise not operator.</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<span class="token">!</span> <em class="replaceable"><code>expression</code></em>

<span class="token">~</span> <em class="replaceable"><code>expression</code></em>
	    </pre></div></blockquote></div><p>
	  The result of the <span class="token">!</span>
	  operator is a logical opposite of its right hand side
	  expression. If the right hand side expression evaluated to a logical true,
	  the result is a logical false. If it evaluated to a logical false, the result
	  is a logical true.</p><p>
	  <span class="command"><strong>maildrop</strong></span> uses the following concept of true/false:
	  an empty text
	  literal, or a text literal that consists of the single character "0" is a
	  logical false value. Anything else is a logical true value.</p><p>
	  The result of the <span class="token">~</span>
	  operator is a bitwise complement of its right hand
	  side expression. The right hand side expression is evaluated as a 32 bit
	  integer, and the result of this operator is a bitwise complement of the
	  result.</p></div><div class="refsect3"><a id="idm46044388759248" shape="rect"> </a><h4>escape(string) - escape special characters in a string.</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
<code class="function">escape</code>(<em class="replaceable"><code>expression</code></em>)
	    </pre></div></blockquote></div><p>
	  The <code class="function">escape</code> function returns
	  its sole argument with every occurrence of a
	  special character prefixed by a backslash. A special character is any of the
	  following characters:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
|!$()[]\+*?.&amp;;`'-~&lt;&gt;^{}"
	    </pre></div></blockquote></div><p>
	  This can used when <a class="ulink" href="#patmatch" target="_top" shape="rect">matching pattern sections</a>,
	  and then taking one section and matching it again. For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if ( /^From:\s*(.*)/ )
{
   MATCH1=escape($MATCH1)
   if ( /^Subject:.*$MATCH1/ )
   {
      ...
   }
}
	    </pre></div></blockquote></div><p>
	  This example checks if the contents of the <code class="literal">From:</code>
	  header can also be found in the <code class="literal">Subject:</code> header.
	  If the <code class="function">escape</code> function were not used, then any
	  special characters in the <code class="literal">From:</code> header that are also used
	  in regular
	  expressions, such as <span class="token">*</span>
	  or <span class="token">+</span>, would introduce unpredictable behavior, most
	  likely a syntax error.</p><p>
	  The reason why this list of special characters also includes characters
	  not used in <span class="command"><strong>maildrop</strong></span>'s regular expressions is to allow
	  <span class="command"><strong>maildrop</strong></span>'s variables to be used on the command line of a
	  shell command
	  executed by the <span class="command"><strong>xfilter</strong></span> command, backtick characters, or
	  <span class="command"><strong>to</strong></span> or <span class="command"><strong>cc</strong></span> commands.</p><p>
	  Although using data from an external data source is dangerous, and it may
	  result in inadvertent exploits, using the escape function should hopefully
	  result in fewer surprises.</p></div><div class="refsect3"><a id="idm46044388742592" shape="rect"> </a><h4>gdbmopen, gdbmclose, gdbmfetch, gdbmstore - GDBM support in
	  <span class="command"><strong>maildrop</strong></span></h4><p>
	  These functions provide support for GDBM database files. See <a class="ulink" href="maildropgdbm.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">maildropgdbm</span>(5)</span></a>
	  for more information.</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    The system administrator can disable GDBM support in
	    <span class="command"><strong>maildrop</strong></span>, so these commands may not be available to
	    you.</p></div></div><div class="refsect3"><a id="idm46044388738176" shape="rect"> </a><h4>getaddr(string) - extract RFC 2822 addresses from a header.</h4><a id="getaddr" shape="rect"> </a><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if ( /^From:\s*(.*)/ )
{
   ADDR=getaddr($MATCH1)
}
	    </pre></div></blockquote></div><p>
	  This function is usually applied to a header that contains
	  <a class="ulink" href="http://www.rfc-editor.org/rfc/rfc2822.txt" target="_top" shape="rect">RFC 2822</a>
	  addresses. It extracts the actual addresses from the
	  header, without any comments or extraneous punctuation. Each address is
	  followed by a newline character. For example,
	  if <em class="replaceable"><code>string</code></em> contains:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
joe@domain.com (Joe Brown), "Alex Smith" &lt;alex@domain.com&gt;, tom@domain.com
	    </pre></div></blockquote></div><p>
	  The result of the <code class="function">getaddr</code> function is the
	  following string:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
joe@domain.com<span class="token">&lt;NL&gt;</span>alex@domain.com<span class="token">&lt;NL&gt;</span>tom@domain.com<span class="token">&lt;NL&gt;</span>
	    </pre></div></blockquote></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    Because <code class="function">getaddr</code>() interprets
	    <a class="ulink" href="http://www.rfc-editor.org/rfc/rfc822.txt" target="_top" shape="rect">RFC 2822</a>
	    loosely, it is not
	    necessary to
	    strip off the "<code class="literal">To:</code>" or the "<code class="literal">Cc:</code>"
	    header from the string, before feeding it to
	    <code class="function">getaddr()</code>. For example, the following snippet of code
	    takes all
	    addresses in the message, and concatenates them into a single string,
	    separated by spaces:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
ADDRLIST=""
foreach /^(To|Cc): .*/
{
    foreach (getaddr $MATCH) =~ /.+/
    {
        ADDRLIST="$ADDRLIST $MATCH"
    }
}
	      </pre></div></blockquote></div></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    In certain rare situations,
	    <a class="ulink" href="http://www.rfc-editor.org/rfc/rfc822.txt" target="_top" shape="rect">RFC 2822</a> allows
	    spaces to be included in E-mail addresses, so this example is just
	    educational.</p></div></div><div class="refsect3"><a id="idm46044388721376" shape="rect"> </a><h4>hasaddr(string) - Search for an address.</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if ( hasaddr(<em class="replaceable"><code>string</code></em>) )
{
   ...
}
	    </pre></div></blockquote></div><p>
	  "<em class="replaceable"><code>string</code></em>" is of the form
	  <code class="literal">user@domain</code>. The hasaddr
	  function returns 1 if this address is included in any <code class="literal">To:</code>,
	  <code class="literal">Cc:</code>,<code class="literal"> Resent-To:</code>, or <code class="literal">Resent-Cc:</code>, header
	  in the message, otherwise this function returns 0.</p><p>
	  This is more than just a simple text search. Each header is parsed
	  according to <code class="literal">RFC822</code>. Addresses found in the header are
	  extracted, ignoring all comments and names. The remaining addresses are
	  checked, and if "<em class="replaceable"><code>string</code></em>" is one of them,
	  <code class="function">hasaddr</code> returns 1,
	  otherwise it returns 0.</p><p>The comparison is case-insensitive. This actually violates
	  <code class="literal">RFC822</code> (and several others) a little bit, because the user part
	  of the address may be (but is not required to be) case sensitive.</p></div><div class="refsect3"><a id="idm46044388711296" shape="rect"> </a><h4>length (string) - length of a string</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if (length(<em class="replaceable"><code>string</code></em>) &gt; 80)
{
   ...
}
	    </pre></div></blockquote></div><p>
	  The <code class="function">length</code> function returns the number of characters in
	  <em class="replaceable"><code>string</code></em>.</p></div><div class="refsect3"><a id="idm46044388707280" shape="rect"> </a><h4>lookup (expr, 'filename', 'options') - read file for patterns</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if (lookup(<em class="replaceable"><code>expr</code></em>, <code class="filename">file</code>, "<em class="replaceable"><code>option</code></em>"))
{
   ...
}
	    </pre></div></blockquote></div><p>
	  <em class="replaceable"><code>expr</code></em> is any expression.
	  <code class="filename">filename</code> is a name of a file containing
	  a list of patterns. Note that <code class="filename">filename</code> is relative to the
	  current directory, which is the home directory of the user when
	  <span class="command"><strong>maildrop</strong></span> runs in delivery mode, or embedded mode. <span class="command"><strong>maildrop</strong></span> then
	  reads the file.
	  Blank lines will be ignored, as well as any lines that begin
	  with the # character (comments).</p><p>Leading whitespace (but not trailing whitespace, take care) is removed,
	  and the remaining contents of each line are interpreted as a pattern which is
	  matched against <em class="replaceable"><code>expr</code></em>.
	  As soon as the match is found, <code class="function">lookup</code>
	  returns "1". If no match is found after reading the entire file,
	  <code class="function">lookup</code> returns "0". For example:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
if ( /^To:\s*(.*)/ &amp;&amp; lookup( $MATCH1, "badto.dat" ))
{
    exit
}
	    </pre></div></blockquote></div><p>
	  The file badto.dat contains the following two lines:</p><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
friend@public
^[^@]*$
	    </pre></div></blockquote></div><p>
	  If a message has a <code class="literal">To:</code>
	  header that contains the text "<code class="literal">friend@public</code>", or does
	  not contain at least one <span class="token">@</span> character, then the message will
	  be silently
	  dropped on the floor ( <span class="command"><strong>maildrop</strong></span> will terminate without
	  delivering the
	  message anywhere).</p><p>
	  <em class="replaceable"><code>options</code></em> are the pattern matching options
	  to use. The only supported
	  option is "D" (the rest are meaningless, in this case).</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>
	    Be careful with discarding messages like that. Pattern matching can
	    be tricky, and a slight miscalculation can cause mail to be unintentionally
	    discarded. It is much desirable to first deliver message to a separate folder
	    or mailbox, and once the filter is verified to work correctly, change it so
	    the messages are discarded completely.</p></div></div><div class="refsect3"><a id="idm46044388689792" shape="rect"> </a><h4>substr(string,start [,count]) - return substring</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
foo=substr($foo, 1, 10)
	    </pre></div></blockquote></div><p>
	  The <code class="function">substr</code> function
	  extracts characters from <em class="replaceable"><code>string</code></em>
	  beginning with character #<em class="replaceable"><code>start</code></em>.
	  If <em class="replaceable"><code>count</code></em> is
	  specified, at most <em class="replaceable"><code>count</code></em> characters
	  starting at position <em class="replaceable"><code>start</code></em> are kept, any excess is
	  trimmed.</p></div><div class="refsect3"><a id="idm46044388684704" shape="rect"> </a><h4>time - return current time</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
foo=time
	    </pre></div></blockquote></div><p>
	  The <code class="function">time</code> function returns the current time, in
	  seconds, since
	  January 1, 1970. This function is useful when using GDBM files. See <a class="ulink" href="maildropex.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">maildropex</span>(7)</span></a>
	  for an example of using the <code class="function">time</code> function.</p></div><div class="refsect3"><a id="idm46044388679632" shape="rect"> </a><h4>tolower(string) - Convert string to lowercase.</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
foo=tolower(<em class="replaceable"><code>string</code></em>)
	    </pre></div></blockquote></div><p>
	  This function returns the <em class="replaceable"><code>string</code></em>
	  with all uppercase characters
	  replaced by lowercase characters.</p></div><div class="refsect3"><a id="idm46044388676240" shape="rect"> </a><h4>toupper(string) - Convert string to uppercase.</h4><div class="blockquote"><blockquote class="blockquote"><div class="informalexample"><pre class="programlisting" xml:space="preserve">
foo=toupper(<em class="replaceable"><code>string</code></em>)
	    </pre></div></blockquote></div><p>
	  This function returns the <em class="replaceable"><code>string</code></em>
	  with all lowercase characters
	  replaced by uppercase characters.</p></div></div><div class="refsect2"><a id="idm46044388672720" shape="rect"> </a><h3>Statements</h3><p>
	The <code class="systemitem">filter file</code> is read by
	<span class="command"><strong>maildrop</strong></span>
	(<code class="filename">$HOME/.mailfilter</code> or another file), and it
	contains filtering
	statements, one per line. The filtering language used by
	<span class="command"><strong>maildrop</strong></span> has
	a loosely - defined grammatical structure.</p><p>Statements are listed one per line. Multiple statements may be listed on
	the same line by separating them with semicolons. To continue a long
	statement on the next line, terminate the line with a backslash
	character.</p></div></div><div class="refsect1"><a id="idm46044388668192" shape="rect"> </a><h2>BUGS</h2><p>
      If <code class="function">getaddr</code>() or <code class="function">hasaddr</code>()
      functions are used on broken headers, the results
      are unpredictable.</p><p><code class="function">hasaddr</code>() is completely case insensitive. This
      actually violates a few
      RFCs, because the userid portion of the address could be case-sensitive, but
      it's not in too many cases, so there.</p></div><div class="refsect1"><a id="idm46044388664608" shape="rect"> </a><h2>SEE ALSO</h2><p>
      <a class="ulink" href="lockmail.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">lockmail</span>(1)</span></a>,
      <a class="ulink" href="maildrop.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">maildrop</span>(1)</span></a>,
      <a class="ulink" href="maildropgdbm.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">maildropgdbm</span>(5)</span></a>,
      <a class="ulink" href="maildirquota.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">maildirquota</span>(8)</span></a>,
      <a class="ulink" href="reformail.html" target="_top" shape="rect"><span class="citerefentry"><span class="refentrytitle">reformail</span>(1)</span></a>,
      <span class="citerefentry"><span class="refentrytitle">egrep</span>(1)</span>,
      <span class="citerefentry"><span class="refentrytitle">sendmail</span>(8)</span>.
    </p></div></div></body></html>
