Fix minor faults in documentation of release handling

Fix typos or minor faults.

Move out code listing of target_system.erl, and use codeinclude
statement to include this file from sasl/examples directory.

4 files changed, 84 insertions, 296 deletions

diff --git a/lib/sasl/doc/src/release_handler.xml b/lib/sasl/doc/src/release_handler.xml
index bd4a513750..e3438ede41 100644
--- a/lib/sasl/doc/src/release_handler.xml
+++ b/lib/sasl/doc/src/release_handler.xml
@@ -64,10 +64,10 @@
       downgraded to the specified version by evaluating the instructions
       in <c>relup</c>. An installed release can be made
       <em>permanent</em>. There can only be one permanent release in
-      the system, and this is the release that is used if the system is
-      restarted. An installed release, except the permanent one, can be
-      <em>removed</em>. When a release is removed, all files that
-      belong to that release only are deleted.</p>
+      the system, and this is the release that is used if the system
+      is restarted. An installed release, except the permanent one,
+      can be <em>removed</em>. When a release is removed, all files
+      that belong to that release only are deleted.</p>
     <p>Each version of the release has a status. The status can be
       <c>unpacked</c>, <c>current</c>, <c>permanent</c>, or <c>old</c>.
       There is always one latest release which either has status
@@ -107,16 +107,17 @@ old        reboot_old            permanent
       restarted. This is taken care of automatically if Erlang is
       started as an embedded system. Read about this in <em>Embedded System</em>. In this case, the system configuration file
       <c>sys.config</c> is mandatory.</p>
-    <p>A new release may restart the system. Which program to use is
-      specified by the SASL configuration parameter <c>start_prg</c>
-      which defaults to <c>$ROOT/bin/start</c>.</p>
+    <p>The installation of a new release may restart the system. Which
+      program to use is specified by the SASL configuration
+      parameter <c>start_prg</c> which defaults
+      to <c>$ROOT/bin/start</c>.</p>
     <p>The emulator restart on Windows NT expects that the system is
       started using the <c>erlsrv</c> program (as a service).
       Furthermore the release handler expects that the service is named 
       <em>NodeName</em>_<em>Release</em>, where <em>NodeName</em> is
       the first part of the Erlang nodename (up to, but not including
-      the "@") and <em>Release</em> is the current release of
-      the application. The release handler furthermore expects that a
+      the "@") and <em>Release</em> is the current version of
+      the release. The release handler furthermore expects that a
       program like <c>start_erl.exe</c> is specified as "machine" to
       <c>erlsrv</c>. During upgrading with restart, a new service will
       be registered and started. The new service will be set to
@@ -484,7 +485,7 @@ release_handler:set_unpacked(RelFile, [{myapp,"1.0","/home/user"},...]).
         <c>release_handler</c> to end up in an inconsistent state.</p>
       <p>No persistent information is updated, why these functions can
         be used on any Erlang node, embedded or not. Also, using these
-        functions does not effect which code will be loaded in case of
+        functions does not affect which code will be loaded in case of
         a reboot.</p>
       <p>If the upgrade or downgrade fails, the application may end up
         in an inconsistent state.</p>
diff --git a/system/doc/design_principles/release_handling.xml b/system/doc/design_principles/release_handling.xml
index 8ed36f3c56..4378b6599c 100644
--- a/system/doc/design_principles/release_handling.xml
+++ b/system/doc/design_principles/release_handling.xml
@@ -178,13 +178,13 @@
     <marker id="instr"></marker>
     <title>Release Handling Instructions</title>
     <p>OTP supports a set of <em>release handling instructions</em>
-      that is used when creating <c>.appup</c> files. The release
+      that are used when creating <c>.appup</c> files. The release
       handler understands a subset of these, the <em>low-level</em>
       instructions. To make it easier for the user, there are also a
       number of <em>high-level</em> instructions, which are translated
       to low-level instructions by <c>systools:make_relup</c>.</p>
     <p>Here, some of the most frequently used instructions are
-      described. The complete list of instructions is found in
+      described. The complete list of instructions can be found in
       <c>appup(4)</c>.</p>
     <p>First, some definitions:</p>
     <taglist>
@@ -239,9 +239,10 @@
       <p><c>update</c> with argument <c>supervisor</c> is used when
         changing the start specification of a supervisor. See
         <seealso marker="appup_cookbook#sup">Appup Cookbook</seealso>.</p>
-      <p>The release handler finds the processes <em>using</em> a module
-        to update by traversing the supervision tree of each running
-        application and checking all the child specifications:</p>
+      <p>When a module is to be updated, the release handler finds
+        which processes that are <em>using</em> the module by
+        traversing the supervision tree of each running application
+        and checking all the child specifications:</p>
       <code type="none">
 {Id, StartFunc, Restart, Shutdown, Type, Modules}</code>
       <p>A process is using a module if the name is listed in
@@ -265,8 +266,8 @@
       <p>The instruction loads the module and is absolutely necessary
         when running Erlang in embedded mode. It is not strictly
         required when running Erlang in interactive (default) mode,
-        since the code server automatically searches for and loads
-        unloaded modules.</p>
+        since the code server then automatically searches for and
+        loads unloaded modules.</p>
       <p>The opposite of <c>add_module</c> is <c>delete_module</c> which
         unloads a module:</p>
       <code type="none">
@@ -294,7 +295,7 @@
         the modules are unloaded using a number of <c>delete_module</c>
         instructions and then the application specification is unloaded
         from the application controller.</p>
-      <p>Instruction for removing an application:</p>
+      <p>Instruction for restarting an application:</p>
       <code type="none">
 {restart_application, Application}</code>
       <p>Restarting an application means that the application is stopped
@@ -331,17 +332,17 @@
         of the emulator and the core applications. Then it shuts down
         the current emulator by calling <c>init:reboot()</c>, see
         <c>init(3)</c>. All processes are terminated gracefully and
-        the system can then be rebooted by the heart program, using
-        the temporary boot file. After the reboot, the rest of the
-        relup instructions are executed. This is done as a part of the
-        boot script.</p>
+        the system is rebooted by the heart program, using the
+        temporary boot file. After the reboot, the rest of the relup
+        instructions are executed. This is done as a part of the
+        temporary boot script.</p>
       <p>An info report is written when the upgrade is completed. To
         programatically find out if the upgrade is complete,
-        call <c>release_handler:which_releases/0</c> and check if the
-        expected release has status <c>current</c>.</p>
-      <p>The new version must be made permanent when the new emulator
-        is up and running. Otherwise, the old version will be used in
-        case of a new system reboot.</p>
+        call <c>release_handler:which_releases(current)</c> and check
+        if it returns the expected (i.e. the new) release.</p>
+      <p>The new release version must be made permanent when the new
+        emulator is up and running. Otherwise, the old version will be
+        used in case of a new system reboot.</p>
       <p>On UNIX, the release handler tells the heart program which
         command to use to reboot the system. Note that the environment
         variable <c>HEART_COMMAND</c>, normally used by the heart
@@ -362,8 +363,8 @@
 	a relup script, and it shall always be placed at the end. If
 	the relup is generated by <c>systools:make_relup/3,4</c> this
 	is automatically ensured.</p>
-      <p>When the release handler encounters the instruction, it shuts down
-        the emulator by calling <c>init:reboot()</c>, see
+      <p>When the release handler encounters the instruction, it shuts
+        down the emulator by calling <c>init:reboot()</c>, see
         <c>init(3)</c>. All processes are terminated gracefully and
         the system can then be rebooted by the heart program using the
         new release version. No more upgrade instruction will be
@@ -581,8 +582,8 @@ release_handler:remove_release(Vsn) => ok</code>
 [].</code>
     <p>2) Start the system as a simple target system. Note that in
       reality, it should be started as an embedded system. However,
-      using <c>erl</c> with the correct boot script and <c>.config</c>
-      file is enough for illustration purposes:</p>
+      using <c>erl</c> with the correct boot script and config file is
+      enough for illustration purposes:</p>
     <pre>
 % <input>cd $ROOT</input>
 % <input>bin/erl -boot $ROOT/releases/A/start -config $ROOT/releases/A/sys</input>
@@ -617,6 +618,7 @@ lib/ch_app-2/ebin/ch3.beam
 releases/B/start.boot
 releases/B/relup
 releases/B/sys.config
+releases/B/ch_rel-2.rel
 releases/ch_rel-2.rel</code>
     <p>4) Copy the release package <c>ch_rel-2.tar.gz</c> to
       the <c>$ROOT/releases</c> directory.</p>
diff --git a/system/doc/design_principles/release_structure.xml b/system/doc/design_principles/release_structure.xml
index 2e1daa611a..8aea0e1a10 100644
--- a/system/doc/design_principles/release_structure.xml
+++ b/system/doc/design_principles/release_structure.xml
@@ -4,7 +4,7 @@
 <chapter>
   <header>
     <copyright>
-      <year>2003</year><year>2009</year>
+      <year>2003</year><year>2011</year>
       <holder>Ericsson AB. All Rights Reserved.</holder>
     </copyright>
     <legalnotice>
@@ -61,12 +61,14 @@
   {ApplicationN, AppVsnN}]}.</code>
     <p>The file must be named <c>Rel.rel</c>, where <c>Rel</c> is a
       unique name.</p>
-    <p><c>Name</c>, <c>Vsn</c> and <c>Evsn</c> are strings.</p>
+    <p><c>Name</c>, <c>Vsn</c> and <c>EVsn</c> are strings.</p>
     <p>Each <c>Application</c> (atom) and <c>AppVsn</c> (string) is
       the name and version of an application included in the release.
-      Note the the minimal release based on Erlang/OTP consists of
+      Note that the minimal release based on Erlang/OTP consists of
       the <c>kernel</c> and <c>stdlib</c> applications, so these
       applications must be included in the list.</p>
+    <p>If the release is to be upgraded, it must also include
+      the <c>sasl</c> application.</p>
     <marker id="ch_rel"></marker>
     <p>Example: We want to make a release of <c>ch_app</c> from
       the <seealso marker="applications#ch_app">Applications</seealso>
@@ -173,6 +175,7 @@ lib/ch_app-1/ebin/ch_app.beam
 lib/ch_app-1/ebin/ch_sup.beam
 lib/ch_app-1/ebin/ch3.beam
 releases/A/start.boot
+releases/A/ch_rel-1.rel
 releases/ch_rel-1.rel</pre>
     <p>Note that a new boot script was generated, without
       the <c>local</c> option set, before the release package was made.
@@ -180,6 +183,17 @@ releases/ch_rel-1.rel</pre>
       under <c>lib</c>. Also, we do not know where the release package
       will be installed, so we do not want any hardcoded absolute paths
       in the boot script here.</p>
+    <p>The release resource file <c>mysystem.rel</c> is duplicated in
+      the tar file. Originally, this file was only stored in
+      the <c>releases</c> directory in order to make it possible for
+      the <c>release_handler</c> to extract this file
+      separately. After unpacking the tar file, <c>release_handler</c>
+      would automatically copy the file
+      to <c>releases/FIRST</c>. However, sometimes the tar file is
+      unpacked without involving the <c>release_handler</c> (e.g. when
+      unpacking the first target system) and therefore the file is now
+      instead duplicated in the tar file so no manual copying is
+      necessary.</p>
     <p>If a <c>relup</c> file and/or a system configuration file called
       <c>sys.config</c> is found, these files are included in
       the release package as well. See
diff --git a/system/doc/system_principles/create_target.xmlsrc b/system/doc/system_principles/create_target.xmlsrc
index 1564423e00..bc2a76db47 100644
--- a/system/doc/system_principles/create_target.xmlsrc
+++ b/system/doc/system_principles/create_target.xmlsrc
@@ -44,9 +44,9 @@
       may be irrelevant for the purpose in question. Thus, there is a
       need to be able to create a new system based on a given
       Erlang/OTP system, where dispensable applications are removed,
-      and a set of new applications that are included in the new
-      system. Documentation and source code is irrelevant and is
-      therefore not included in the new system.</p>
+      and a set of new applications are included. Documentation and
+      source code is irrelevant and is therefore not included in the
+      new system.</p>
     <p>This chapter is about creating such a system, which we call a
       <em>target system</em>.</p>
     <p>In the following sections we consider creating target systems with
@@ -63,10 +63,11 @@
     </list>
     <p>We only consider the case when Erlang/OTP is running on a UNIX
       system.</p>
-    <p>There is an example Erlang module <c>target_system.erl</c> that
-      contains functions for creating and installing a target system.
-      That module is used in the examples below. The source code of
-      the module is listed at the end of this chapter.</p>
+    <p>In the <c>sasl</c> application there is an example Erlang
+      module <c>target_system.erl</c> that contains functions for
+      creating and installing a target system.  This module is used in
+      the examples below, and the source code of the module is listed
+      at the end of this chapter.</p>
   </section>
 
   <section>
@@ -117,28 +118,41 @@ os> <input>erl -pa /home/user/target_system/myapps/pea-1.0/ebin</input></pre>
         <code type="none">
 erts-5.1/bin/
 releases/FIRST/start.boot
+releases/FIRST/mysystem.rel
 releases/mysystem.rel
 lib/kernel-2.7/
 lib/stdlib-1.10/
 lib/sasl-1.9.3/
 lib/pea-1.0/        </code>
         <p>The file <c>releases/FIRST/start.boot</c> is a copy of our
-          <c>mysystem.boot</c>, and a copy of the original
-          <c>mysystem.rel</c> has been put in the <c>releases</c>
-          directory.</p>
+          <c>mysystem.boot</c></p>
+	<p>The release resource file <c>mysystem.rel</c> is duplicated
+          in the tar file. Originally, this file was only stored in
+          the <c>releases</c> directory in order to make it possible
+          for the <c>release_handler</c> to extract this file
+          separately. After unpacking the tar
+          file, <c>release_handler</c> would automatically copy the
+          file to <c>releases/FIRST</c>. However, sometimes the tar
+          file is unpacked without involving
+          the <c>release_handler</c> (e.g. when unpacking the first
+          target system) and therefore the file is now instead
+          duplicated in the tar file so no manual copying is
+          necessary.</p>
       </item>
       <item>Creates the temporary directory <c>tmp</c> and extracts the tar file
       <c>mysystem.tar.gz</c> into that directory. </item>
       <item>Deletes the <c>erl</c> and <c>start</c> files from
-      <c>tmp/erts-5.1/bin</c>. XXX Why.</item>
+      <c>tmp/erts-5.1/bin</c>. These files will be created again from
+      source when installing the release.</item>
       <item>Creates the directory <c>tmp/bin</c>.</item>
-      <item>Copies the previously creates file <c>plain.boot</c> to
+      <item>Copies the previously created file <c>plain.boot</c> to
       <c>tmp/bin/start.boot</c>.</item>
       <item>Copies the files <c>epmd</c>, <c>run_erl</c>, and
       <c>to_erl</c> from the directory <c>tmp/erts-5.1/bin</c> to
        the directory <c>tmp/bin</c>.</item>
-      <item>Creates the file <c>tmp/releases/start_erl.data</c> with the
-       contents "5.1 FIRST".
+      <item>Creates the file <c>tmp/releases/start_erl.data</c> with
+       the contents "5.1 FIRST". This file is to be passed as data
+       file to the <c>start_erl</c> script.
       </item>
       <item>Recreates the file <c>mysystem.tar.gz</c> from the directories
        in the directory <c>tmp</c>, and removes <c>tmp</c>.</item>
@@ -210,7 +224,7 @@ os> <input>/usr/local/erl-target/bin/erl -boot /usr/local/erl-target/releases/FI
       file of the release version found
       (<c>"releases/FIRST/start.boot"</c>).</p>
     <p><c>start_erl</c> also assumes that there is <c>sys.config</c> in
-      release version directory (<c>"releases/FIRST/sys.config</c>). That
+      release version directory (<c>"releases/FIRST/sys.config"</c>). That
       is the topic of the next section (see below).</p>
     <p>The <c>start_erl</c> shell script should normally not be
       altered by the user.</p>
@@ -222,7 +236,7 @@ os> <input>/usr/local/erl-target/bin/erl -boot /usr/local/erl-target/releases/FI
       <c>sys.config</c> in the release version directory
       (<c>"releases/FIRST/sys.config"</c>). If there is no such a
       file, the system start will fail. Hence such a file has to
-      added as well.</p>
+      be added as well.</p>
     <p></p>
     <p>If you have system configuration data that are neither file
       location dependent nor site dependent, it may be convenient to
@@ -245,252 +259,9 @@ os> <input>/usr/local/erl-target/bin/erl -boot /usr/local/erl-target/releases/FI
 
   <section>
     <title>Listing of target_system.erl</title>
-    <code type="none"><![CDATA[
--module(target_system).
--include_lib("kernel/include/file.hrl").
--export([create/1, install/2]).
--define(BUFSIZE, 8192).
+    <p>This module can also be found in the <c>examples</c> directory
+      of the <c>sasl</c> application.</p>
+    <codeinclude file="../../../lib/sasl/examples/src/target_system.erl" tag="%module" type="erl"></codeinclude>
 
-%% Note: RelFileName below is the *stem* without trailing .rel,
-%% .script etc.
-%%
-
-%% create(RelFileName)
-%%
-create(RelFileName) ->
-    RelFile = RelFileName ++ ".rel",
-    io:fwrite("Reading file: \"~s\" ...~n", [RelFile]),
-    {ok, [RelSpec]} = file:consult(RelFile),
-    io:fwrite("Creating file: \"~s\" from \"~s\" ...~n",
-              ["plain.rel", RelFile]),
-    {release,
-     {RelName, RelVsn},
-     {erts, ErtsVsn},
-     AppVsns} = RelSpec,
-    PlainRelSpec = {release,
-                    {RelName, RelVsn},
-                    {erts, ErtsVsn},
-                    lists:filter(fun({kernel, _}) ->
-                                         true;
-                                    ({stdlib, _}) ->
-                                         true;
-                                    (_) ->
-                                         false
-                                 end, AppVsns)
-                   },
-    {ok, Fd} = file:open("plain.rel", [write]),
-    io:fwrite(Fd, "~p.~n", [PlainRelSpec]),
-    file:close(Fd),
-
-    io:fwrite("Making \"plain.script\" and \"plain.boot\" files ...~n"),
-    make_script("plain"),
-
-    io:fwrite("Making \"~s.script\" and \"~s.boot\" files ...~n",
-              [RelFileName, RelFileName]),
-    make_script(RelFileName),
-
-    TarFileName = io_lib:fwrite("~s.tar.gz", [RelFileName]),
-    io:fwrite("Creating tar file \"~s\" ...~n", [TarFileName]),
-    make_tar(RelFileName),
-
-    io:fwrite("Creating directory \"tmp\" ...~n"),
-    file:make_dir("tmp"),
-
-    io:fwrite("Extracting \"~s\" into directory \"tmp\" ...~n", [TarFileName]),
-    extract_tar(TarFileName, "tmp"),
-
-    TmpBinDir = filename:join(["tmp", "bin"]),
-    ErtsBinDir = filename:join(["tmp", "erts-" ++ ErtsVsn, "bin"]),
-    io:fwrite("Deleting \"erl\" and \"start\" in directory \"~s\" ...~n",
-              [ErtsBinDir]),
-    file:delete(filename:join([ErtsBinDir, "erl"])),
-    file:delete(filename:join([ErtsBinDir, "start"])),
-
-    io:fwrite("Creating temporary directory \"~s\" ...~n", [TmpBinDir]),
-    file:make_dir(TmpBinDir),
-
-    io:fwrite("Copying file \"plain.boot\" to \"~s\" ...~n",
-              [filename:join([TmpBinDir, "start.boot"])]),
-    copy_file("plain.boot", filename:join([TmpBinDir, "start.boot"])),
-
-    io:fwrite("Copying files \"epmd\", \"run_erl\" and \"to_erl\" from \n"
-              "\"~s\" to \"~s\" ...~n",
-              [ErtsBinDir, TmpBinDir]),
-    copy_file(filename:join([ErtsBinDir, "epmd"]),
-              filename:join([TmpBinDir, "epmd"]), [preserve]),
-    copy_file(filename:join([ErtsBinDir, "run_erl"]),
-              filename:join([TmpBinDir, "run_erl"]), [preserve]),
-    copy_file(filename:join([ErtsBinDir, "to_erl"]),
-              filename:join([TmpBinDir, "to_erl"]), [preserve]),
-
-    StartErlDataFile = filename:join(["tmp", "releases", "start_erl.data"]),
-    io:fwrite("Creating \"~s\" ...~n", [StartErlDataFile]),
-    StartErlData = io_lib:fwrite("~s ~s~n", [ErtsVsn, RelVsn]),
-    write_file(StartErlDataFile, StartErlData),
-
-    io:fwrite("Recreating tar file \"~s\" from contents in directory "
-              "\"tmp\" ...~n", [TarFileName]),
-    {ok, Tar} = erl_tar:open(TarFileName, [write, compressed]),
-    {ok, Cwd} = file:get_cwd(),
-    file:set_cwd("tmp"),
-    erl_tar:add(Tar, "bin", []),
-    erl_tar:add(Tar, "erts-" ++ ErtsVsn, []),
-    erl_tar:add(Tar, "releases", []),
-    erl_tar:add(Tar, "lib", []),
-    erl_tar:close(Tar),
-    file:set_cwd(Cwd),
-    io:fwrite("Removing directory \"tmp\" ...~n"),
-    remove_dir_tree("tmp"),
-    ok.
-
-
-install(RelFileName, RootDir) ->
-    TarFile = RelFileName ++ ".tar.gz",
-    io:fwrite("Extracting ~s ...~n", [TarFile]),
-    extract_tar(TarFile, RootDir),
-    StartErlDataFile = filename:join([RootDir, "releases", "start_erl.data"]),
-    {ok, StartErlData} = read_txt_file(StartErlDataFile),
-    [ErlVsn, RelVsn| _] = string:tokens(StartErlData, " \n"),
-    ErtsBinDir = filename:join([RootDir, "erts-" ++ ErlVsn, "bin"]),
-    BinDir = filename:join([RootDir, "bin"]),
-    io:fwrite("Substituting in erl.src, start.src and start_erl.src to\n"
-              "form erl, start and start_erl ...\n"),
-    subst_src_scripts(["erl", "start", "start_erl"], ErtsBinDir, BinDir,
-                      [{"FINAL_ROOTDIR", RootDir}, {"EMU", "beam"}],
-                      [preserve]),
-    io:fwrite("Creating the RELEASES file ...\n"),
-    create_RELEASES(RootDir,
-                    filename:join([RootDir, "releases", RelFileName])).
-
-%% LOCALS
-
-%% make_script(RelFileName)
-%%
-make_script(RelFileName) ->
-    Opts = [no_module_tests],
-    systools:make_script(RelFileName, Opts).
-
-%% make_tar(RelFileName)
-%%
-make_tar(RelFileName) ->
-    RootDir = code:root_dir(),
-    systools:make_tar(RelFileName, [{erts, RootDir}]).
-
-%% extract_tar(TarFile, DestDir)
-%%
-extract_tar(TarFile, DestDir) ->
-    erl_tar:extract(TarFile, [{cwd, DestDir}, compressed]).
-
-create_RELEASES(DestDir, RelFileName) ->
-    release_handler:create_RELEASES(DestDir, RelFileName ++ ".rel").
-
-subst_src_scripts(Scripts, SrcDir, DestDir, Vars, Opts) ->
-    lists:foreach(fun(Script) ->
-                          subst_src_script(Script, SrcDir, DestDir,
-                                           Vars, Opts)
-                  end, Scripts).
-
-subst_src_script(Script, SrcDir, DestDir, Vars, Opts) ->
-    subst_file(filename:join([SrcDir, Script ++ ".src"]),
-               filename:join([DestDir, Script]),
-               Vars, Opts).
-
-subst_file(Src, Dest, Vars, Opts) ->
-    {ok, Conts} = read_txt_file(Src),
-    NConts = subst(Conts, Vars),
-    write_file(Dest, NConts),
-    case lists:member(preserve, Opts) of
-        true ->
-            {ok, FileInfo} = file:read_file_info(Src),
-            file:write_file_info(Dest, FileInfo);
-        false ->
-            ok
-    end.
-
-%% subst(Str, Vars)
-%% Vars = [{Var, Val}]
-%% Var = Val = string()
-%% Substitute all occurrences of %Var% for Val in Str, using the list
-%% of variables in Vars.
-%%
-subst(Str, Vars) ->
-    subst(Str, Vars, []).
-
-subst([$%, C| Rest], Vars, Result) when $A =< C, C =< $Z ->
-    subst_var([C| Rest], Vars, Result, []);
-subst([$%, C| Rest], Vars, Result) when $a =< C, C =< $z ->
-    subst_var([C| Rest], Vars, Result, []);
-subst([$%, C| Rest], Vars, Result) when  C == $_ ->
-    subst_var([C| Rest], Vars, Result, []);
-subst([C| Rest], Vars, Result) ->
-    subst(Rest, Vars, [C| Result]);
-subst([], _Vars, Result) ->
-    lists:reverse(Result).
-
-subst_var([$%| Rest], Vars, Result, VarAcc) ->
-    Key = lists:reverse(VarAcc),
-    case lists:keysearch(Key, 1, Vars) of
-        {value, {Key, Value}} ->
-            subst(Rest, Vars, lists:reverse(Value, Result));
-        false ->
-            subst(Rest, Vars, [$%| VarAcc ++ [$%| Result]])
-    end;
-subst_var([C| Rest], Vars, Result, VarAcc) ->
-    subst_var(Rest, Vars, Result, [C| VarAcc]);
-subst_var([], Vars, Result, VarAcc) ->
-    subst([], Vars, [VarAcc ++ [$%| Result]]).
-
-copy_file(Src, Dest) ->
-    copy_file(Src, Dest, []).
-
-copy_file(Src, Dest, Opts) ->
-    {ok, InFd} = file:open(Src, [raw, binary, read]),
-    {ok, OutFd} = file:open(Dest, [raw, binary, write]),
-    do_copy_file(InFd, OutFd),
-    file:close(InFd),
-    file:close(OutFd),
-    case lists:member(preserve, Opts) of
-        true ->
-            {ok, FileInfo} = file:read_file_info(Src),
-            file:write_file_info(Dest, FileInfo);
-        false ->
-            ok
-    end.
-
-do_copy_file(InFd, OutFd) ->
-    case file:read(InFd, ?BUFSIZE) of
-        {ok, Bin} ->
-            file:write(OutFd, Bin),
-            do_copy_file(InFd, OutFd);
-        eof  ->
-            ok
-    end.
-
-write_file(FName, Conts) ->
-    {ok, Fd} = file:open(FName, [write]),
-    file:write(Fd, Conts),
-    file:close(Fd).
-
-read_txt_file(File) ->
-    {ok, Bin} = file:read_file(File),
-    {ok, binary_to_list(Bin)}.
-
-remove_dir_tree(Dir) ->
-    remove_all_files(".", [Dir]).
-
-remove_all_files(Dir, Files) ->
-    lists:foreach(fun(File) ->
-                          FilePath = filename:join([Dir, File]),
-                          {ok, FileInfo} = file:read_file_info(FilePath),
-                          case FileInfo#file_info.type of
-                              directory ->
-                                  {ok, DirFiles} = file:list_dir(FilePath),
-                                  remove_all_files(FilePath, DirFiles),
-                                  file:del_dir(FilePath);
-                              _ ->
-                                  file:delete(FilePath)
-                          end
-                  end, Files).
-    ]]></code>
   </section>
 </chapter>