lfs-book/chapter06/file-inst.xml

<sect2>
<title>Installation of File</title>

<para>Note that the sed used in this installation only works if the line
break is placed exactly where it below. Don't try and put it
all on one line otherwise it won't work.</para>

<para>Install File by running the following commands:</para>

<para><screen><userinput>cp readelf.h readelf.h.backup &amp;&amp;</userinput>
<userinput>sed '/#define __/a \</userinput>
<userinput>&nbsp;&nbsp;&nbsp;#include &lt;stdint.h&gt;' readelf.h.backup &gt; readelf.h &amp;&amp;</userinput>
<userinput>./configure --prefix=/usr --datadir=/usr/share/misc &amp;&amp;</userinput>
<userinput>make &amp;&amp;</userinput>
<userinput>make install</userinput></screen></para>

<para>File uses magic numbers to determine a file type. These magic numbers 
come with File in a plain text file.  File internally compiles this database 
each time it is run. This is not the normal type of operation for File since 
compiling a
plain text file each time is not the fastest way to do it. File offers an
option "-C" to compile this magic number file. The reason this isn't done
automatically is that some people like to work on the magic numbers.  On the
other hand many people didn't get it that they should compile the magic
numbers, so the author of File added a warning when the plain text magic file
is used. As we usually won't work on the plain text magic file, we 
compile this file, because it's faster, fixes that annoying warning and is how
it was meant to be:</para>

<para><screen><userinput>file -C</userinput></screen></para>

</sect2>