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<html>
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    <title>execline: the runblock program</title>
    <meta name="Description" content="execline: the runblock program" />
    <meta name="Keywords" content="execline command runblock" />
    <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> -->
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<body>

<p>
<a href="index.html">execline</a><br />
<a href="http://skarnet.org/software/">Software</a><br />
<a href="http://skarnet.org/">www.skarnet.org</a>
</p>

<h1> The <tt>runblock</tt> program </h1>

<p>
<tt>runblock</tt>'s purpose is to help you write execline commands
in the execline language. It can only be used inside an execline
script. If the script has been given blocks as arguments, <tt>runblock</tt>
allows you to execute one of the blocks individually.
</p>

<h2> Interface </h2>

<pre>
     runblock [ -P ] [ -n <em>argshift</em> ] [ -r ] <em>n</em>
</pre>

<ul>
 <li> <tt>runblock</tt> skips the first <em>argshift</em> positional
parameters. It does that to allow you to design commands that take simple
arguments <em>and</em> blocks. </li>
 <li> Then <tt>runblock</tt> looks for and parses
<a href="el_semicolon.html">blocks</a> in the positional parameters. </li>
 <li> If the <tt>-r</tt> option is present: <tt>runblock</tt> skips
<em>n</em> blocks and execs into the remaining arguments. </li>
 <li> Else it skips <em>n</em>-1 blocks and execs into the <em>n</em>th
one. </li>
 <li> Normally <tt>runblock</tt> <a href="el_pushenv.html#pop">pops</a>
its environment frame before executing. If the <tt>-P</tt> option has
been given, it <em>does not</em> pop. </li>
 <li> Of course, if the block structure doesn't match, <tt>runblock</tt>
exits 100 with an error message. </li>
</ul>

<h2> Example: implementing the <a href="ifelse.html">ifelse</a> command </h2>

<p>
 Suppose that we want to implement the <a href="ifelse.html">ifelse</a> command as
an execline script, using the <a href="ifte.html">ifte</a> command.
<tt>runblock</tt> allows us to do it in a simple way:
</p>

<pre>
 #!/command/execlineb
 ifte { runblock 2 } { runblock -r 2 } runblock 1
</pre>

<p>
 That's it.
</p>

<h2> Credits </h2>

<p>
 The <tt>runblock</tt> idea, as well as the <tt>ifelse</tt> idea, comes
from <a href="http://code.dogmap.org/">Paul Jarc</a>.
</p>

</body>
</html>