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<h1> The <tt>importas</tt> program </h1>
<p>
<tt>importas</tt> replaces a literal with the value of an
environment variable, then executes another program.
</p>
<h2> Interface </h2>
<pre>
importas [ -i | -D default ] [ -u ] [ -s ] [ -C | -c ] [ -N | -n ] [ -d <em>delim</em> ] <em>variable</em> <em>envvar</em> <em>prog...</em>
importas -S [ -i | -D default ] [ -u ] [ -s ] [ -C | -c ] [ -N | -n ] [ -d <em>delim</em> ] <em>envvar</em> <em>prog...</em>
</pre>
<ul>
<li> <tt>importas</tt> fetches the value of <em>envvar</em> in the
environment. If neither the <em>-D</em> nor the <em>-i</em> option is given,
and <em>envvar</em> is undefined, <strong>no word</strong> is returned
(that is different from the empty word). </li>
<li> <tt>importas</tt> then performs
<a href="el_substitute.html">variable substitution</a> on <em>prog...</em>,
with <em>variable</em> as key and that string as value.
<li><tt>importas</tt> then execs into the modified <em>prog...</em>. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-D</tt> <em>default</em> : If this option is given and
<em>envvar</em> is undefined, substitute <em>default</em> for the value of
<em>variable</em> instead of no word. For instance, to substitute
the empty word, use <tt>-D ""</tt>. </li>
<li> <tt>-i</tt> : Insist. If <em>envvar</em> is undefined,
<tt>importas</tt> will not do anything; instead, it will exit 100 with an
error message. This has precedence over any <tt>-D</tt> option. </li>
<li> <tt>-u</tt> : Unexport. <em>envvar</em> will be removed from
the environment after the substitution. <tt>importas -u <em>variable</em>
<em>envvar</em></tt> is equivalent to <tt>importas <em>variable</em>
<em>envvar</em> unexport <em>envvar</em></tt>. </li>
<li> <tt>-S</tt> : import with same name. This option allows
<em>variable</em> to be omitted; it will be the same as <em>envvar</em>.
In other words, <code>importas -S <em>var</em></code> is the same as
<code>importas <em>var</em> <em>var</em></code>. </li>
<li> Other options are used to <a href="el_transform.html">control
the substitution mechanism</a>. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> When <em>envvar</em> is undefined, and the <tt>-D</tt> option is
not given, any <a href="el_substitute.html">variable substitution</a>
with <em>variable</em> as the key will return no word; that is true
even when the <tt>${<em>variable</em>}</tt> form to be substituted
happens in the middle of a word (with a prefix and/or a postfix), which
means the whole word will be deleted. If this is not the behaviour
you want, use the <tt>-D</tt> option. </li>
</ul>
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