<sect1 id="scripts-bash-environment">

    <title>The Execution Environment</title>

    <para>

        The execution environment of <command>centos-art.sh</command>

        script is organized in four levels.  The first level is the

        <quote>shell environment</quote>, the second level is the

        <quote>command environment</quote>, the third level is the

        <quote>common functions environment</quote> and, finally, the

        fourth level which contains the <quote>specific function

        environment</quote>, as described in 

        linkend="scripts-bash-environment-example1" />.  In this

        context, child environments inherit definitions (e.g.,

        variables and functions) from their parent environments making

        possible to logically organize the script in a way that needs

        can be isolated one another to follow the paradigm proposed by

        Unix developers at Bell Labs when felt that programs

        <quote>should do one thing well.</quote>

    </para>

    <example id="scripts-bash-environment-example1">

    <title>The execution environment</title>

    <screenshot>

    <screeninfo>The execution environment</screeninfo>

    <mediaobject>

    <textobject>

<programlisting>

+-----------------------------------------------------+

| Shell environment                                   |

+---|-------------------|-----------------|-----------+

.   |-- TCAR_WORKDIR    |-- TCAR_BRAND    |-- EDITOR  .

.   |-- LANG            |-- HOME          |-- PATH    .

.   `-- centos-art.sh   `-- TMPDIR        `-- ...     .

.   +---|-----------------------------------------+   .

.   | Command environment                         |   .

.   +---|---------------|----------------|--------+   .

.   .   |-- CLI_NAME    |-- CLI_VERSION  `-- ...  .   .

.   .   |-- CLI_FUNCDIR `-- CLI_BASEDIR           .   .

.   .   `-- cli()                                 .   .

.   .   +---|-----------------------------------+ .   .

.   .   | Common functions environment          | .   .

.   .   +---|------------------------|----------+ .   .

.   .   .   |-- cli_printMessage()   |-- ...    . .   .

.   .   .   |-- cli_getFilesList()   |-- ...    . .   .

.   .   .   `-- render()             `-- ...    . .   .

.   .   .   +---|---------------------------+   . .   .

.   .   .   | Specific function environment |   . .   .

.   .   .   +-------------------------------+   . .   .

.   .   ......................................... .   .

.   ...............................................   .

.......................................................

</programlisting>

    </textobject>

    </mediaobject>

    </screenshot>

    </example>

    <sect2>

    <title>The Shell Environment</title>

    <para>

        The <command>centos-art.sh</command> script uses the following

        shell environment variables:

    </para>

    <variablelist>

    <varlistentry>

    <term><envar>PATH</envar></term>

    <listitem>

    <para>

        The <envar>PATH</envar> environment variable is specific to

        the operating system and provides search paths for command

        execution.  By default, the <command>centos-art.sh</command>

        script links executable scripts from the 

        class="directory">~/bin</filename> directory which is one of

        the locations used as search path in this variable. This is

        how we create the <command>centos-art</command> command from

        the <command>centos-art.sh</command> script inside your

        working copy.

    </para>

    <para>

        This variable is not initialized inside the

        <command>centos-art.sh</command> script. Instead, the value

        set in <filename>~/.bash_profile</filename> file is used. 

    </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><envar>EDITOR</envar></term>

    <listitem>

    <para>

        The <envar>EDITOR</envar> environment variable is specific to

        the operating system and provides the path to your default

        text editor. The <command>centos-art.sh</command> script uses

        the default text editor to edit subversion pre-commit

        messages, translation files, documentation files, script

        files, and similar text-based files.  

    </para>

    <para>

        Possible values for this variable are:

    </para>

    <itemizedlist>

        <listitem>

        <para>

            <filename class="directory">/usr/bin/vim</filename>

        </para>

        </listitem>

        <listitem>

        <para>

        <filename class="directory">/usr/bin/emacs</filename>

        </para>

        </listitem>

        <listitem>

        <para>

            <filename class="directory">/usr/bin/nano</filename>

        </para>

        </listitem>

    </itemizedlist>

    <para>

        In case none of these values is set for the

        <envar>EDITOR</envar> environment variable inside

        <filename>~/.bash_profile</filename>, the

        <command>centos-art.sh</command> script uses 

        class="directory">/usr/bin/vim</filename> as default text

        editor. This is the text editor installed by default in &TC;;. 

    </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><varname>TEXTDOMAIN</varname></term>

    <listitem>

    <para>

        The <envar>TEXTDOMAIN</envar> environment variable is specific

        to the operating system and provides the domain name of that

        application we are producing translation messages for. This

        variable, in combination with <envar>TEXTDOMAINDIR</envar>, is

        used by <application>gettext</application> to find out the

        location of translation messages.  In the very specific case

        of <command>centos-art.sh</command> script we use the

        <literal>centos-art.sh</literal> name as domain name.

    </para>

    <para>

        This variable is initialized inside the

        <command>centos-art.sh</command> script, so if you set it

        outside it (e.g., in <filename>~/.bash_profile</filename>) the

        value you set there will be overwritten by that one set inside

        <command>centos-art.sh</command> script, once it is executed.

    </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><varname>TEXTDOMAINDIR</varname></term>

    <listitem>

    <para>

        The <envar>TEXTDOMAINDIR</envar> environment variable is

        specific to the operating system and provides the absolute

        path to the directory containing the translation messages

        related to that application specified by

        <envar>TEXTDOMAIN</envar> environment variable.  In the very

        specific case of <command>centos-art.sh</command> script we

        use the 

        class="directory">Locales/Scripts/Bash</filename>

        path as default value.

    </para>

    <para>

        This variable is initialized inside the

        <command>centos-art.sh</command> script, so if you set it

        outside it (e.g., in <filename>~/.bash_profile</filename>) the

        value you set there will be overwritten by that one set inside

        <command>centos-art.sh</command> script, once it is executed.

    </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><envar>TMPDIR</envar></term>

    <listitem>

    <para>

        The <envar>TMPDIR</envar> environment variable is specific to

        the operating system and provides the absolute path to the

        temporal directory the centos-art.sh script will use along its

        execution. This variable is defined inside the

        <command>centos-art.sh</command> script itself using the

        <command>mktemp</command> command and will be unique on each

        script execution. Thus, you should be able to run several

        instances of <command>centos-art.sh</command> script

        simultaneously without any problem. 

    </para>

    <para>

        When you contribute code to <command>centos-art.sh</command>

        script and need to create temporal files, do it inside the

        absolute path specified by this variable.

    </para>

    <para>

        This variable is redefined inside the

        <command>centos-art.sh</command> script, so if you set it

        outside it (e.g., in <filename>~/.bash_profile</filename>) the

        value you set there will be overwritten by that one set inside

        <command>centos-art.sh</command> script, once it is executed.

    </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><envar>LANG</envar></term>

    <listitem>

    <para>

        The <envar>LANG</envar> environment variable is specific to

        the operating system and controls the default locale

        information of it.  The <command>centos-art.sh</command>

        script use the <envar>LANG</envar> environment variable to

        determine what language to use for printing output messages

        from the script itself, as well as the portable objects

        locations that need to be updated or edited when you localize

        directory structures inside the working copy of &TCAR;.

    </para>

    <para>

        The <envar>LANG</envar> environment variable is initially set

        in the installation process of &TC;;, specifically in the

        <emphasis>Language</emphasis> step.  Generally, there is no

        need to customize this variable in your personal profile. If

        you need to change the value of this environment variable do

        it through the login screen of GNOME Desktop Environment or

        the <command>system-config-language</command> command, or even

        resetting the variable before executing the

        <command>centos-art.sh</command> script.

    </para>

    </listitem>

    </varlistentry>

    </variablelist>

    <para>

        In addition to shell environment variables described above,

        the <command>centos-art.sh</command> script adds the following

        variables inside the <filename>~/.bash_profile</filename> file

        to control the script behaviour in a per-user level:

    </para>

    <variablelist>

    <varlistentry>

    <term><varname>TCAR_WORKDIR</varname></term>

    <listitem>

    <para>

        The <envar>TCAR_WORKDIR</envar> environment variable is

        specific to <command>centos-art.sh</command> script and

        controls the working copy default location of &TCAR;.  This is

        the place in your workstation where &TCAR; file system is

        stored for you to work with it.

    </para>

    <para>

        By default, just after installing your workstation, this

        variable will not be found in it and the

        <command>centos-art.sh</command> script will finish its

        execution with an error message if you try to execute it

        without any argument. This behaviour is OK because the

        <command>centos-art.sh</command> script doesn't know where you

        stored the working copy of &TCAR; in your workstation. In

        order for this variable to exist in your workstation you need

        to configure your workstation first, as described in 

        linkend="repo-ws-config" />.

    </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><varname>TCAR_BRAND</varname></term>

    <listitem>

    <para>

        The <envar>TCAR_BRAND</envar> environment variable is specific

        to <command>centos-art.sh</command> script and controls the

        brand information that identifies the content produced inside

        &TCAR;. The brand information is used to give name to some

        files inside the repository (e.g., see files under 

        class="directory">Identity/Models/Brands</filename>

        directory).

    </para>

    <para>

        By default, this variable takes <quote>centos</quote> as

        value. In case you want to change it to something else, you

        should consider the following implications:

    </para>

    <itemizedlist>

    <listitem>

    <para>

        The <command>centos-art.sh</command> script will no longer be

        referred as such. Instead, the

        <filename>${TCAR_BRAND}-art.sh</filename> name will be used.

        This implies that you no longer are using the

        <command>centos-art.sh</command> file we provide as part of

        &TCAR; and won't be able to commit changes to it. However, if

        you retain the same logic from

        <command>centos-art.sh</command> script in

        <filename>${TCAR_WORKDIR}-art.sh</filename>, you can use

        common and specific functionalities provided by

        <command>centos-art.sh</command> script and commit changes to

        them.

    </para>

    </listitem>

    <listitem>

    <para>

        The files stored under 

        class="directory">Identity/Models/Brands</filename>

        should be named using the value of

        <literal>${TCAR_BRAND}</literal> as section. If you change

        the value of this variable, you need to be sure the new value

        set does coincide with the file names you use to store brand

        information.

    </para>

    </listitem>

    </itemizedlist>

    </listitem>

    </varlistentry>

    </variablelist>

    </sect2>

    <sect2>

    <title>The Command Environment</title>

    <para>

        The first file the <command>centos-art.sh</command> script

        calls is the

        <filename>Scripts/Bash/Functions/Commons/cli.sh</filename>

        file. This file initializes all variables and functions you

        will be able to use along the script execution environment

        lifetime.  Such environment variables are for internal use

        inside the <command>centos-art.sh</command> script only and

        users shouldn't modify them to customize the script in a

        per-user level.  Instead, to customize the script behaviour in

        a per-user level, you need to make use of your personal

        environment variables set in the

        <filename>~/.bash_profile</filename> file.

    </para>

    <para>

        Once environment variables are initialized, the

        <command>centos-art.sh</command> script initializes common and

        specific environment functions, in that order.

    </para>

    <sect3>

    <title>Common Function Environment</title>

    <para>

        Common function environments are stored under 

        class="directory">Scripts/Bash/Functions/Commons</filename>

        directory and will be available always, both for common

        environment functions themselves and specific environment

        functions.

    </para>

    </sect3>

    <sect3>

    <title>Specific Function Environments</title>

    <para>

        Specific function environments, on the other hand, are stored

        in the 

        class="directory">Scripts/Bash/Functions/${CLI_FUNCDIRNAM}/${CLI_FUNCNAME}.sh</filename>

        file, where:

    </para>

    <variablelist>

    <varlistentry>

    <term><varname>CLI_FUNCDIRNAME</varname></term>

    <listitem>

    <para>

        Is the first argument passed to

        <command>centos-art.sh</command> script with the first letter

        in uppercase but the rest in lowercase. For example,

        <literal>Render</literal>, <literal>Locale</literal> and

        <literal>Help</literal> are all possible values to this

        variable.

     </para>

    </listitem>

    </varlistentry>

    <varlistentry>

    <term><varname>CLI_FUNCNAME</varname></term>

    <listitem>

    <para>

        Is the first argument passed to

        <command>centos-art.sh</command> script with all letters in

        lowercase. For example, <literal>render</literal>,

        <literal>locale</literal> and <literal>help</literal> are all

        possible values to this variable. 

    </para>

    </listitem>

    </varlistentry>

    </variablelist>

    <para>

        Specific functions environment can be written in just one file

        or in several files inside the same directory. Using one file

        to write specific functions environment is rarely seen inside

        the <command>centos-art.sh</command> script but it could

        happen in situations where the need you want to solve can be

        written in a few lines inside just one file. On the other

        hand, if you find yourself writing a too long file, it is

        convenient to logically divide it into several files. This

        logical division takes place using functions, which indeed

        create other environments where you can create and express

        your solutions.

    </para>

    <para>

        The order in which individual files are exported and executed

        inside the specific functions environments depends in the way

        each developer write the 

        class="directory">Scripts/Bash/Functions/${CLI_FUNCDIRNAM}/${CLI_FUNCNAME}.sh</filename>

        file. This is the main file inside the specific function

        environment and controls the kind of logical division you

        implement to organize the solution you need. As file name

        convention, the following structure for new specific functions

        environment is proposed:

    </para>

<programlisting>

Scripts/Bash/Functions/${CLI_FUNCDIRNAM}/

|-- ${CLI_FUNCNAME}.sh

`-- ${CLI_FUNCNAME}_verbSubject.sh

</programlisting>

    <para>

        Specific functions environment is exported after common

        functions environment does, so it is not possible for specific

        functions environment to be available inside the common

        functions environment, nor inside other specific functions

        environment, different to the one been passed as first

        argument to the <command>centos-art.sh</command> script

        command-line.<footnote>

            <para>

                Although, it is possible for you to call the

                <command>centos-art.sh</command> script to itself

                through the <function>cli_runFnEnvironment</function>

                common function environment.

            </para>

        </footnote> In 

        linkend="scripts-bash-environment-example1" />,

        <function>render</function> is a specific function environment

        while <function>cli_printMessage</function> and

        <function>cli_getFilesList</function> are common function

        environments.

    </para>

    <para>

        Both specific and common function environments exist to

        standardize frequent tasks inside &TCAR;. The following

        sections will describe which these frequent tasks are and the

        way they are standardized using specific and common function

        environments.

    </para>

    </sect3>

    </sect2>

</sect1>