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<title>avram - a virtual machine code interpreter: 1.2.2 Parameter Mode</title>

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<a name="Parameter-Mode"></a>
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<a name="Parameter-Mode-1"></a>
<h3 class="subsection">1.2.2 Parameter Mode</h3>
<a name="index-parameter-mode"></a>
<p>In parameter mode, the argument to the function given by the virtual
code is a data structure containing environment variables and command
line parameters including files, application specific options, and
possibly standard input. The result obtained by evaluating the
function is either a data structure representing a set of files to be
written, which may include standard output, or a sequence of shell
commands to be executed, or a combination of both. Parameter mode is
indicated whenever either of these conditions is met.
</p>
<ul>
<li>
Any of the parameter mode options appears on the
command line preceding the first filename parameter.
<br>
See section <a href="Parameter-Mode-Options.html#Parameter-Mode-Options">Parameter Mode Options</a>.
</li><li>
At least one additional filename parameter or option follows the first
filename parameter, and the option &lsquo;<samp>--unparameterized</samp>&rsquo; does not
precede it.
</li></ul>
 
<p>Examples:
</p>
<dl compact="compact">
<dt> <kbd>avram --map-to-each-file prettyprinter.avm *.c *.h --extra-pretty</kbd></dt>
<dd><p>In this example, parameter mode is indicated both by the parameter
mode option &lsquo;<samp>--map-to-each-file</samp>&rsquo; and by the presence of input
file names and the &lsquo;<samp>--extra-pretty</samp>&rsquo; option. The latter is
specific to the hypothetical <code>prettyprinter.avm</code> virtual code
application, as indicated by its position on the command line, and is
therefore passed to it by <code>avram</code>.
</p></dd>
<dt> <kbd>cat ~/specfile | avram reportgenerator -v - /var/log/syslog</kbd></dt>
<dd><p>In this example, a hypothetical parameter mode application
<code>reportgenerator</code> is able to read &lsquo;<tt>~/specfile</tt>&rsquo; from standard
input because of the <code>-</code> used as a parameter.
</p></dd>
<dt> <kbd>avram --parameterized grepenv</kbd></dt>
<dd><p>In this example, a hypothetical application that searches shell
variables is invoked in parameter mode even with no input files or
application specific options, because of the  &lsquo;<samp>--parameterized</samp>&rsquo;
option. Parameter mode invocation is required by the application to give
it access to the environment.
</p></dd>
<dt> <kbd>avram grepenv --search-targets=PATH,MANPATH</kbd></dt>
<dd><p>This example shows an application specific option with both a keyword
and a parameter list. They suffice to indicate parameter mode without
an explicit &lsquo;<samp>--parameterized</samp>&rsquo; option.
</p></dd>
</dl>

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