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<h4 class="subsection">10.4.5 Details of Tilde Expansion</h4>

<p>It's a standard part of shell syntax that you can use &lsquo;<samp><span class="samp">~</span></samp>&rsquo; at the
beginning of a file name to stand for your own home directory.  You
can use &lsquo;<samp><span class="samp">~</span><var>user</var></samp>&rsquo; to stand for <var>user</var>'s home directory.

   <p><dfn>Tilde expansion</dfn> is the process of converting these abbreviations
to the directory names that they stand for.

   <p>Tilde expansion applies to the &lsquo;<samp><span class="samp">~</span></samp>&rsquo; plus all following characters up
to whitespace or a slash.  It takes place only at the beginning of a
word, and only if none of the characters to be transformed is quoted in
any way.

   <p>Plain &lsquo;<samp><span class="samp">~</span></samp>&rsquo; uses the value of the environment variable <code>HOME</code>
as the proper home directory name.  &lsquo;<samp><span class="samp">~</span></samp>&rsquo; followed by a user name
uses <code>getpwname</code> to look up that user in the user database, and
uses whatever directory is recorded there.  Thus, &lsquo;<samp><span class="samp">~</span></samp>&rsquo; followed
by your own name can give different results from plain &lsquo;<samp><span class="samp">~</span></samp>&rsquo;, if
the value of <code>HOME</code> is not really your home directory.

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