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<h4 class="subsection">3.4.2 Commands Dealing with Files</h4>

<p><a name="index-linker-script-file-commands-397"></a>Several linker script commands deal with files.

     <dl>
<dt><code>INCLUDE </code><var>filename</var><dd><a name="index-INCLUDE-_0040var_007bfilename_007d-398"></a><a name="index-including-a-linker-script-399"></a>Include the linker script <var>filename</var> at this point.  The file will
be searched for in the current directory, and in any directory specified
with the <samp><span class="option">-L</span></samp> option.  You can nest calls to <code>INCLUDE</code> up to
10 levels deep.

     <p>You can place <code>INCLUDE</code> directives at the top level, in <code>MEMORY</code> or
<code>SECTIONS</code> commands, or in output section descriptions.

     <br><dt><code>INPUT(</code><var>file</var><code>, </code><var>file</var><code>, ...)</code><dt><code>INPUT(</code><var>file</var> <var>file</var><code> ...)</code><dd><a name="index-INPUT_0028_0040var_007bfiles_007d_0029-400"></a><a name="index-input-files-in-linker-scripts-401"></a><a name="index-input-object-files-in-linker-scripts-402"></a><a name="index-linker-script-input-object-files-403"></a>The <code>INPUT</code> command directs the linker to include the named files
in the link, as though they were named on the command line.

     <p>For example, if you always want to include <samp><span class="file">subr.o</span></samp> any time you do
a link, but you can't be bothered to put it on every link command line,
then you can put &lsquo;<samp><span class="samp">INPUT (subr.o)</span></samp>&rsquo; in your linker script.

     <p>In fact, if you like, you can list all of your input files in the linker
script, and then invoke the linker with nothing but a &lsquo;<samp><span class="samp">-T</span></samp>&rsquo; option.

     <p>In case a <dfn>sysroot prefix</dfn> is configured, and the filename starts
with the &lsquo;<samp><span class="samp">/</span></samp>&rsquo; character, and the script being processed was
located inside the <dfn>sysroot prefix</dfn>, the filename will be looked
for in the <dfn>sysroot prefix</dfn>.  Otherwise, the linker will try to
open the file in the current directory.  If it is not found, the
linker will search through the archive library search path. 
The <dfn>sysroot prefix</dfn> can also be forced by specifying <code>=</code>
as the first character in the filename path, or prefixing the filename
path with <code>$SYSROOT</code>.  See also the description of &lsquo;<samp><span class="samp">-L</span></samp>&rsquo; in
<a href="Options.html#Options">Command-line Options</a>.

     <p>If you use &lsquo;<samp><span class="samp">INPUT (-l</span><var>file</var><span class="samp">)</span></samp>&rsquo;, <samp><span class="command">ld</span></samp> will transform the
name to <code>lib</code><var>file</var><code>.a</code>, as with the command-line argument
&lsquo;<samp><span class="samp">-l</span></samp>&rsquo;.

     <p>When you use the <code>INPUT</code> command in an implicit linker script, the
files will be included in the link at the point at which the linker
script file is included.  This can affect archive searching.

     <br><dt><code>GROUP(</code><var>file</var><code>, </code><var>file</var><code>, ...)</code><dt><code>GROUP(</code><var>file</var> <var>file</var><code> ...)</code><dd><a name="index-GROUP_0028_0040var_007bfiles_007d_0029-404"></a><a name="index-grouping-input-files-405"></a>The <code>GROUP</code> command is like <code>INPUT</code>, except that the named
files should all be archives, and they are searched repeatedly until no
new undefined references are created.  See the description of &lsquo;<samp><span class="samp">-(</span></samp>&rsquo;
in <a href="Options.html#Options">Command-line Options</a>.

     <br><dt><code>AS_NEEDED(</code><var>file</var><code>, </code><var>file</var><code>, ...)</code><dt><code>AS_NEEDED(</code><var>file</var> <var>file</var><code> ...)</code><dd><a name="index-AS_005fNEEDED_0028_0040var_007bfiles_007d_0029-406"></a>This construct can appear only inside of the <code>INPUT</code> or <code>GROUP</code>
commands, among other filenames.  The files listed will be handled
as if they appear directly in the <code>INPUT</code> or <code>GROUP</code> commands,
with the exception of ELF shared libraries, that will be added only
when they are actually needed.  This construct essentially enables
<samp><span class="option">--as-needed</span></samp> option for all the files listed inside of it
and restores previous <samp><span class="option">--as-needed</span></samp> resp. <samp><span class="option">--no-as-needed</span></samp>
setting afterwards.

     <br><dt><code>OUTPUT(</code><var>filename</var><code>)</code><dd><a name="index-OUTPUT_0028_0040var_007bfilename_007d_0029-407"></a><a name="index-output-file-name-in-linker-script-408"></a>The <code>OUTPUT</code> command names the output file.  Using
<code>OUTPUT(</code><var>filename</var><code>)</code> in the linker script is exactly like using
&lsquo;<samp><span class="samp">-o </span><var>filename</var></samp>&rsquo; on the command line (see <a href="Options.html#Options">Command Line Options</a>).  If both are used, the command-line option takes
precedence.

     <p>You can use the <code>OUTPUT</code> command to define a default name for the
output file other than the usual default of <samp><span class="file">a.out</span></samp>.

     <br><dt><code>SEARCH_DIR(</code><var>path</var><code>)</code><dd><a name="index-SEARCH_005fDIR_0028_0040var_007bpath_007d_0029-409"></a><a name="index-library-search-path-in-linker-script-410"></a><a name="index-archive-search-path-in-linker-script-411"></a><a name="index-search-path-in-linker-script-412"></a>The <code>SEARCH_DIR</code> command adds <var>path</var> to the list of paths where
<samp><span class="command">ld</span></samp> looks for archive libraries.  Using
<code>SEARCH_DIR(</code><var>path</var><code>)</code> is exactly like using &lsquo;<samp><span class="samp">-L </span><var>path</var></samp>&rsquo;
on the command line (see <a href="Options.html#Options">Command-line Options</a>).  If both
are used, then the linker will search both paths.  Paths specified using
the command-line option are searched first.

     <br><dt><code>STARTUP(</code><var>filename</var><code>)</code><dd><a name="index-STARTUP_0028_0040var_007bfilename_007d_0029-413"></a><a name="index-first-input-file-414"></a>The <code>STARTUP</code> command is just like the <code>INPUT</code> command, except
that <var>filename</var> will become the first input file to be linked, as
though it were specified first on the command line.  This may be useful
when using a system in which the entry point is always the start of the
first file. 
</dl>

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