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<title>execline: the envfile program</title>
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<h1> The <tt>envfile</tt> program </h1>
<p>
<tt>envfile</tt> reads a file containing variable assignments,
adds the variables to the environment, then executes a program.
</p>
<h2> Interface </h2>
<pre>
envfile <em>file</em> <em>prog...</em>
</pre>
<p>
<tt>envfile</tt> reads <em>file</em> and adds the key-value pairs
defined in <em>file</em> to the environment. Then it
execs into <em>prog...</em>, i.e. the rest of its command line,
with the modified environment.
</p>
<h2> Exit codes </h2>
<ul>
<li> 1: syntax error in <em>file</em> </li>
<li> 100: wrong usage </li>
<li> 111: system call failed </li>
<li> 126: execve() on <em>prog</em> failed (unknown reason) </li>
<li> 127: execve() on <em>prog</em> failed (<em>prog</em> could not be found) </li>
</ul>
<p>
0 is not listed because on success, <tt>envfile</tt> does not exit:
it execs into <em>prog</em>.
</p>
<h2> File syntax </h2>
<p>
<em>file</em> is a text file containing lines of the form <tt>key = value</tt>.
Whitespace is permitted before and after <em>key</em>, and before or after <em>value</em>,
but <em>key</em> or <em>value</em> can never contain whitespace. No quoting
is possible.
</p>
<p>
Empty lines, or lines containing only whitespace, are ignored.
Lines beginning with <tt>#</tt> (possibly after some whitespace)
are ignored (and typically used for comments).
Comments are also possible at the end of lines:
<tt>key = value # comment</tt> is a valid line. Note that there
<em>must</em> be whitespace between <em>value</em> and <tt>#</tt>
in this case (else <tt>#</tt> is just read as a part of <em>value</em>).
</p>
<p>
If <em>value</em> is empty, <em>key</em> is <strong>still</strong>
added to the environment, with an empty value. If you do not want
<em>key</em> to be added to the environment at all, comment out the line.
<tt>envfile</tt> does not offer a way to <em>remove</em> variables from
the environment.
</p>
<h2> Notes </h2>
<ul>
<li> If <em>file</em> is <tt>-</tt> then <tt>envfile</tt> reads
and parses its standard input instead. To read a file literally named
<tt>-</tt>, you can use <tt>./-</tt> for instance. </li>
<li> The variables and values that can be defined with <tt>envfile</tt>
are purposefully restricted in order to keep the parsing extremely simple.
If you need fancy values, for instance values that contain whitespace or
a newline, you should use an envdir instead: see
<a href="//skarnet.org/software/s6/s6-envdir.html">s6-envdir</a>. </li>
</ul>
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