1 files changed, 223 insertions, 0 deletions
diff --git a/doc/user/file-removal.in b/doc/user/file-removal.in
new file mode 100644
index 0000000..c26f020
--- /dev/null
+++ b/doc/user/file-removal.in
@@ -0,0 +1,223 @@
+<!--
+
+  Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 The SCons Foundation
+
+  Permission is hereby granted, free of charge, to any person obtaining
+  a copy of this software and associated documentation files (the
+  "Software"), to deal in the Software without restriction, including
+  without limitation the rights to use, copy, modify, merge, publish,
+  distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so, subject to
+  the following conditions:
+
+  The above copyright notice and this permission notice shall be included
+  in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+  KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+  WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+-->
+
+  <para>
+
+  There are two occasions when &SCons; will,
+  by default, remove target files.
+  The first is when &SCons; determines that
+  an target file needs to be rebuilt
+  and removes the existing version of the target
+  before executing
+  The second is when &SCons; is invoked with the
+  <literal>-c</literal> option to "clean"
+  a tree of its built targets.
+
+  These behaviours can be suppressed with the
+  &Precious; and &NoClean; functions, respectively.
+
+  </para>
+
+  <section>
+  <title>Preventing target removal during build: the &Precious; Function</title>
+
+    <para>
+
+    By default, &SCons; removes targets before building them.
+    Sometimes, however, this is not what you want.
+    For example, you may want to update a library incrementally,
+    not by having it deleted and then rebuilt from all
+    of the constituent object files.
+    In such cases, you can use the
+    &Precious; method to prevent
+    &SCons; from removing the target before it is built:
+
+    </para>
+
+    <scons_example name="precious-ex1">
+      <file name="SConstruct" printme="1">
+        env = Environment(RANLIBCOM='')
+        lib = env.Library('foo', ['f1.c', 'f2.c', 'f3.c'])
+        env.Precious(lib)
+      </file>
+      <file name="f1.c">
+      int f1() { }
+      </file>
+      <file name="f2.c">
+      int f2() { }
+      </file>
+      <file name="f3.c">
+      int f3() { }
+      </file>
+    </scons_example>
+
+    <para>
+
+    Although the output doesn't look any different,
+    &SCons; does not, in fact,
+    delete the target library before rebuilding it:
+
+    </para>
+
+    <scons_output example="precious-ex1">
+        <scons_output_command>scons -Q</scons_output_command>
+    </scons_output>
+
+    <para>
+
+    &SCons; will, however, still delete files marked as &Precious;
+    when the <literal>-c</literal> option is used.
+
+    </para>
+
+  </section>
+
+  <section>
+  <title>Preventing target removal during clean: the &NoClean; Function</title>
+
+    <para>
+
+    By default, &SCons; removes all built targets when invoked
+    with the <literal>-c</literal> option to clean a source tree
+    of built targets.
+    Sometimes, however, this is not what you want.
+    For example, you may want to remove only intermediate generated files
+    (such as object files),
+    but leave the final targets
+    (the libraries)
+    untouched.
+
+    In such cases, you can use the &NoClean; method to prevent &SCons;
+    from removing a target during a clean:
+
+    </para>
+
+    <scons_example name="noclean-ex1">
+      <file name="SConstruct" printme="1">
+        env = Environment(RANLIBCOM='')
+        lib = env.Library('foo', ['f1.c', 'f2.c', 'f3.c'])
+        env.NoClean(lib)
+      </file>
+      <file name="f1.c">
+      int f1() { }
+      </file>
+      <file name="f2.c">
+      int f2() { }
+      </file>
+      <file name="f3.c">
+      int f3() { }
+      </file>
+    </scons_example>
+
+    <para>
+
+    Notice that the <filename>libfoo.a</filename>
+    is not listed as a removed file:
+
+    </para>
+
+    <scons_output example="noclean-ex1">
+        <scons_output_command>scons -Q</scons_output_command>
+        <scons_output_command>scons -c</scons_output_command>
+    </scons_output>
+
+  </section>
+
+  <section>
+  <title>Removing additional files during clean: the &Clean; Function</title>
+
+    <para>
+
+    There may be additional files that you want removed
+    when the <literal>-c</literal> option is used,
+    but which &SCons; doesn't know about
+    because they're not normal target files.
+    For example, perhaps a command you invoke
+    creates a log file as
+    part of building the target file you want.
+    You would like the log file cleaned,
+    but you don't want to have to teach
+    SCons that the command
+    "builds" two files.
+
+    </para>
+
+    <para>
+
+    You can use the &Clean; function to arrange for additional files
+    to be removed when the <literal>-c</literal> option is used.
+    Notice, however, that the &Clean; function takes two arguments,
+    and the <emphasis>second</emphasis> argument
+    is the name of the additional file you want cleaned
+    (<filename>foo.log</filename> in this example):
+
+    </para>
+
+    <scons_example name="clean-ex1">
+      <file name="S" printme="1">
+        t = Command('foo.out', 'foo.in', 'build -o $TARGET $SOURCE')
+        Clean(t, 'foo.log')
+      </file>
+      <file name="SConstruct">
+      env = DefaultEnvironment()
+      import os
+      env['ENV']['PATH'] = env['ENV']['PATH'] + os.pathsep + os.getcwd()
+      SConscript('S')
+      </file>
+      <file name="foo.in">
+      foo.in
+      </file>
+      <file name="foo.log">
+      foo.log
+      </file>
+      <file name="build" chmod="0755">
+      cat $3 > $2
+      </file>
+    </scons_example>
+
+    <para>
+
+    The first argument is the target with which you want
+    the cleaning of this additional file associated.
+    In the above example,
+    we've used the return value from the
+    &Command; function,
+    which represents the
+    <filename>foo.out</filename>
+    target.
+    Now whenever the
+    <filename>foo.out</filename> target is cleaned
+    by the <literal>-c</literal> option,
+    the <filename>foo.log</filename> file
+    will be removed as well:
+
+    </para>
+
+    <scons_output example="clean-ex1">
+        <scons_output_command>scons -Q</scons_output_command>
+        <scons_output_command>scons -Q -c</scons_output_command>
+    </scons_output>
+
+  </section>