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|
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Saving Configuration Information
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<div class="SECT1">
<h1 class="SECT1">
<a name="Z79">Saving Configuration Information</a>
</h1>
<p>
<tt class="APPLICATION">libgnome</tt> comes with the
ability to store simple key-value pairs in plain text
configuration files. Convenience routines are provided for
numeric and boolean types which transparently convert to
and from a text representation of each type. The standard
location for Gnome configuration files is <tt class=
"FILENAME">~/.gnome</tt>, and the library will use that
location by default. However, the library can be used with
any file. There are also variants of each function which
save to <tt class="FILENAME">~/.gnome_private</tt>, a
directory with user permissions only. The basic functions
to store and retrieve data are listed in <a href=
"z79.html#STARTUP-GNOMECONFIGGET">Figure 4 in the section
called <i>Reading Stored Config Data</i></a> and <a href=
"z79.html#STARTUP-GNOMECONFIGSET">Figure 5 in the section
called <i>Storing Data In Configuration Files</i></a>. This
module of <tt class="APPLICATION">libgnome</tt> is often
referred to as <tt class="APPLICATION">gnome-config</tt>.
Don't confuse this usage of "gnome-config" with the <tt
class="APPLICATION">gnome-config</tt> script that reports
the compile and link flags for Gnome programs.
</p>
<p>
The <tt class="APPLICATION">gnome-config</tt> functions
work with a <i class="FIRSTTERM">path</i>. A path has three
components:
</p>
<ul>
<li>
<p>
The <i class="FIRSTTERM">filename</i> to use,
underneath the <tt class="FILENAME">~/.gnome</tt> or
<tt class="FILENAME">~/.gnome_private</tt> directory.
By convention this is the name of your application.
</p>
</li>
<li>
<p>
A <i class="FIRSTTERM">section</i>---a logical
subcategory of related configuration information.
</p>
</li>
<li>
<p>
A <i class="FIRSTTERM">key</i>---the key half of a
key-value pair. The key is actually associated with a
piece of configuration data.
</p>
</li>
</ul>
<p>
A path is passed to Gnome as a string, with the form <tt
class="APPLICATION">"/filename/section/key"</tt>. If you
want to use a filename which is <i class="EMPHASIS">not</i>
in the standard Gnome directories, you can bracket the
entire path with the <tt class="APPLICATION">'='</tt>
character and it will be interpreted as absolute. You can
even use this as a simple datafile format (it is used for
the <tt class="APPLICATION">.desktop</tt> files programs
install in order to appear on the Gnome panel menu).
However, XML (perhaps using the <tt class="APPLICATION">
gnome-xml</tt> package) is almost certainly a better choice
for that. XML may also be a better choice for storing some
kinds of configuration information; the primary advantage
of the <tt class="APPLICATION">libgnome</tt> configuration
library is its simplicity.
</p>
<p>
<tt class="APPLICATION">gnome-config</tt> has a long
history; it was first written for the WINE Windows emulator
project, then used in the GNU Midnight Commander file
manager, and finally migrated into the Gnome libraries. The
plan is to replace <tt class="APPLICATION">
gnome-config</tt> with something more powerful in the next
version of Gnome; we want to support per-host
configuration, backends such as LDAP, and other features.
However, the <tt class="APPLICATION">gnome-config</tt> API
will almost certainly be supported even if the underlying
engine changes dramatically.
</p>
<div class="SECT2">
<h2 class="SECT2">
<a name="Z80">Reading Stored Config Data</a>
</h2>
<p>
Retrieving data from files is simple. You simply call a
function to retrieve the value for a given key. The
value-retrieving functions (shown in <a href=
"z79.html#STARTUP-GNOMECONFIGGET">Figure 4</a>) accept a
path as their argument. For example, you might ask
whether the user wants to see a dialog box:
</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
gboolean show_dialog;
show_dialog =
gnome_config_get_bool("/myapp/General/dialog");
</pre>
</td>
</tr>
</table>
<p>
If the config file doesn't exist yet, or there is no key
matching the path you provide, these functions return 0,
<span class="STRUCTNAME">FALSE</span>, or <span class=
"STRUCTNAME">NULL</span>. The functions that return a
string return allocated memory; you should <tt class=
"FUNCTION">g_free()</tt> the returned string. The string
vector functions return an allocated vector full of
allocated strings (<tt class="FUNCTION">g_strfreev()</tt>
is the easiest way to free this vector).
</p>
<p>
You can specify a default value to be returned if the key
does not exist; to do so, append an <span class=
"STRUCTNAME">"=value"</span> to the path. For example:
</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
gboolean show_dialog;
show_dialog =
gnome_config_get_bool("/myapp/General/dialog=true");
</pre>
</td>
</tr>
</table>
<p>
Each function has a <span class="STRUCTNAME">
with_default</span> variant; these tell you whether the
return value was taken from a config file or from the
default you specified. For example:
</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
gboolean show_dialog;
gboolean used_default;
show_dialog =
gnome_config_get_bool_with_default("/myapp/General/dialog=true",
&used_default);
if (used_default)
printf("Default value used for show_dialog\n");
</pre>
</td>
</tr>
</table>
<p>
<tt class="FUNCTION">gnome_config_push_prefix()</tt> and
<tt class="FUNCTION">gnome_config_pop_prefix()</tt> (in
<a href="z79.html#STARTUP-GNOMECONFIGMISC">Figure 7 in
the section called <i>Other Config File
Operations</i></a>) can be used to avoid specifying the
entire path each time. For example:
</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
gboolean show_dialog;
gnome_config_push_prefix("/myapp/General/");
show_dialog =
gnome_config_get_bool("dialog=true");
gnome_config_pop_prefix();
</pre>
</td>
</tr>
</table>
<p>
These functions also work when saving values.
</p>
<p>
The configuration functions with <span class=
"STRUCTNAME">private</span> in their name use a <tt
class="FILENAME">.gnome_private</tt> directory with
restricted permissions, as discussed above. The <span
class="STRUCTNAME">translated_string</span> functions
qualify the provided key with the name of the current
locale; these are used when Gnome reads <tt class=
"APPLICATION">.desktop</tt> files (see <a href=
"z72.html#SEC-.DESKTOP">the section called <i><tt class=
"APPLICATION">.desktop</tt> Entries</i> in the chapter
called <i>Creating Your Source Tree</i></a>) and are
probably not useful to applications.
</p>
<div class="FIGURE">
<a name="STARTUP-GNOMECONFIGGET"></a>
<div class="FUNCSYNOPSIS">
<a name="STARTUP-GNOMECONFIGGET.SYNOPSIS"></a>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="FUNCSYNOPSISINFO">
#include <libgnome/gnome-config.h>
</pre>
</td>
</tr>
</table>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">gnome_config_get_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_get_translated_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gint <tt class=
"FUNCTION">gnome_config_get_int</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gdouble <tt class=
"FUNCTION">gnome_config_get_float</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gboolean <tt class=
"FUNCTION">gnome_config_get_bool</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_get_vector</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint*
<tt class="PARAMETER"><i>argcp</i></tt>, gchar*** <tt
class="PARAMETER"><i>argvp</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_private_get_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_private_get_translated_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gint <tt class=
"FUNCTION">
gnome_config_private_get_int</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gdouble <tt class=
"FUNCTION">
gnome_config_private_get_float</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gboolean <tt class=
"FUNCTION">
gnome_config_private_get_bool</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_get_vector</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint*
<tt class="PARAMETER"><i>argcp</i></tt>, gchar*** <tt
class="PARAMETER"><i>argvp</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_get_string_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_get_translated_string_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gint <tt class=
"FUNCTION">
gnome_config_get_int_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gdouble <tt class=
"FUNCTION">
gnome_config_get_float_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gboolean <tt class=
"FUNCTION">
gnome_config_get_bool_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_get_vector_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint*
<tt class="PARAMETER"><i>argcp</i></tt>, gchar*** <tt
class="PARAMETER"><i>argvp</i></tt>, gboolean* <tt
class="PARAMETER"><i>was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_private_get_string_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_private_get_translated_string_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gint <tt class=
"FUNCTION">
gnome_config_private_get_int_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gdouble <tt class=
"FUNCTION">
gnome_config_private_get_float_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gboolean <tt class=
"FUNCTION">
gnome_config_private_get_bool_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean* <tt class="PARAMETER"><i>
was_default</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_get_vector_with_default</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint*
<tt class="PARAMETER"><i>argcp</i></tt>, gchar*** <tt
class="PARAMETER"><i>argvp</i></tt>, gboolean* <tt
class="PARAMETER"><i>was_default</i></tt>);</code>
</p>
</div>
<p>
<b>Figure 4. Retrieving data from configuration
files</b>
</p>
</div>
</div>
<div class="SECT2">
<h2 class="SECT2">
<a name="Z81">Storing Data In Configuration Files</a>
</h2>
<p>
Saving data is simply the inverse of loading it; you
provide a <span class="STRUCTNAME">
"/file/section/key"</span> path in just the same way,
along with the value to store. Data is not written
immediately; you must call <tt class="FUNCTION">
gnome_config_sync()</tt> to ensure the file is written to
disk.
</p>
<div class="FIGURE">
<a name="STARTUP-GNOMECONFIGSET"></a>
<div class="FUNCSYNOPSIS">
<a name="STARTUP-GNOMECONFIGSET.SYNOPSIS"></a>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="FUNCSYNOPSISINFO">
#include <libgnome/gnome-config.h>
</pre>
</td>
</tr>
</table>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_set_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, const
gchar* <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_set_translated_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, const
gchar* <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_set_int</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint
<tt class="PARAMETER"><i>value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_set_float</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gdouble <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_set_bool</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_set_vector</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint
<tt class="PARAMETER"><i>argc</i></tt>, const gchar*
const <tt class="PARAMETER"><i>
argv[]</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_set_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, const
gchar* <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_set_translated_string</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, const
gchar* <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_set_int</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>, gint <tt
class="PARAMETER"><i>value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_set_float</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gdouble <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_set_bool</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>,
gboolean <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_set_vector</tt></code>(const
gchar* <tt class="PARAMETER"><i>path</i></tt>, gint
<tt class="PARAMETER"><i>argc</i></tt>, const gchar*
const <tt class="PARAMETER"><i>
argv[]</i></tt>);</code>
</p>
</div>
<p>
<b>Figure 5. Saving data to configuration files</b>
</p>
</div>
</div>
<div class="SECT2">
<h2 class="SECT2">
<a name="Z82">Config File Iterators</a>
</h2>
<p>
Iterators are used to scan the sections in a given file,
or the keys in a given section. Applications can use this
feature to store lists of data, by dynamically generating
key or section names to save and later iterating over
them to discover what was saved. The functions are
summarized in <a href=
"z79.html#STARTUP-GNOMECONFIGITERATORS">Figure 6 in the
section called <i>Section Iterators</i></a>.
</p>
<p>
An iterator is an opaque data type; you pass <tt class=
"FUNCTION">gnome_config_init_iterator()</tt> the name of
a section to iterate over and receive an iterator in
return. You then call <tt class="FUNCTION">
gnome_config_iterator_next()</tt> to obtain key-value
pairs from the section. The key and value returned from
<tt class="FUNCTION">gnome_config_iterator_next()</tt>
must be freed with <tt class="FUNCTION">g_free()</tt>,
and the return value of <tt class="FUNCTION">
gnome_config_iterator_next()</tt> is a pointer to the
next iterator. When <tt class="FUNCTION">
gnome_config_iterator_next()</tt> returns <span class=
"STRUCTNAME">NULL</span>, all key-value pairs have been
traversed.
</p>
<div class="SECT3">
<h3 class="SECT3">
<a name="Z83">Iteration Example from <tt class=
"APPLICATION">gnome-apt</tt></a>
</h3>
<p>
Here's an example from <tt class="APPLICATION">
gnome-apt</tt>, a C++ application used to manage
packages on Debian systems. <tt class="APPLICATION">
gnome-apt</tt> loads and saves the position of some
columns in a tree display. The columns are identified
by the <span class="STRUCTNAME">
GAptPkgTree::ColumnType</span> enumeration. <span
class="STRUCTNAME">GAptPkgTree::ColumnTypeEnd</span> is
the last element in the column type enumeration, and
equal to the number of valid column types. This example
is frighteningly "real world" and checks for a number
of error conditions.
</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
static void
load_column_order(vector<GAptPkgTree::ColumnType> & columns)
{
gpointer config_iterator;
guint loaded = 0;
config_iterator = gnome_config_init_iterator("/gnome-apt/ColumnOrder");
if (config_iterator != 0)
{
gchar * col, * pos;
columns.reserve(GAptPkgTree::ColumnTypeEnd);
loaded = 0;
while ((config_iterator =
gnome_config_iterator_next(config_iterator,
&col, &pos)))
{
// shouldn't happen, but I'm paranoid
if (pos == 0 || col == 0)
{
if (pos) g_free(pos);
if (col) g_free(col);
continue;
}
GAptPkgTree::ColumnType ct = string_to_column(col);
gint index = atoi(pos);
g_free(pos); pos = 0;
g_free(col); col = 0;
// the user could mangle the config file to make this happen
if (static_cast<guint>(index) >= columns.size())
continue;
columns[index] = ct;
++loaded;
}
}
if (loaded != static_cast<guint>(GAptPkgTree::ColumnTypeEnd))
{
// Either there was no saved order, or something is busted - use
// default order
columns.clear();
int i = 0;
while (i < GAptPkgTree::ColumnTypeEnd)
{
columns.push_back(static_cast<GAptPkgTree::ColumnType>(i));
++i;
}
// Clean the section - otherwise an old entry could
// remain forever and keep screwing us up in the future.
gnome_config_clean_section("/gnome-apt/ColumnOrder");
gnome_config_sync();
}
g_return_if_fail(columns.size() ==
static_cast<guint>(GAptPkgTree::ColumnTypeEnd));
}
</pre>
</td>
</tr>
</table>
<p>
It might be helpful to see the function that saves the
column positions:
</p>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="PROGRAMLISTING">
static void
save_column_order(const vector<GAptPkgTree::ColumnType> & columns)
{
g_return_if_fail(columns.size() ==
static_cast<guint>(GAptPkgTree::ColumnTypeEnd));
int position = 0;
vector<GAptPkgTree::ColumnType>::const_iterator i = columns.begin();
while (i != columns.end())
{
gchar key[256];
g_snprintf(key, 255, "/gnome-apt/ColumnOrder/%s", column_to_string(*i));
gchar val[30];
g_snprintf(val, 29, "%d", position);
gnome_config_set_string(key, val);
++position;
++i;
}
gnome_config_sync();
}
</pre>
</td>
</tr>
</table>
<p>
When writing this code, the decision was made to store
enumeration values as strings rather than integers. The
<tt class="FUNCTION">column_to_string()</tt> and <tt
class="FUNCTION">string_to_column()</tt> functions use
a simple array of column names indexed by the
enumeration values to convert back and forth. There are
two reasons to do this: it will not break when the
enumeration is altered in future versions of the
program, and it keeps the configuration file
human-editable.
</p>
<p>
You may also notice that the column positions are
stored with <tt class="FUNCTION">
gnome_config_set_string()</tt> instead of <tt class=
"FUNCTION">gnome_config_set_int()</tt>. This is because
<tt class="FUNCTION">gnome_config_iterator_next()</tt>
returns a string representation of the stored
information, as found in the file. Most likely, <tt
class="FUNCTION">gnome_config_set_int()</tt> stores
integers as strings <tt class="FUNCTION">atoi()</tt>
would understand (in fact it does), but it is
technically not guaranteed by the API. If the code used
<tt class="FUNCTION">gnome_config_set_int()</tt>, it
would have to obtain only the key from <tt class=
"FUNCTION">gnome_config_iterator_next()</tt> and then
call <tt class="FUNCTION">gnome_config_get_int()</tt>
to obtain the integer value. Using <tt class=
"FUNCTION">atoi()</tt> on the string value would make
unwarranted assumptions about <tt class="APPLICATION">
gnome-config</tt>'s implementation.
</p>
</div>
<div class="SECT3">
<h3 class="SECT3">
<a name="Z84">Section Iterators</a>
</h3>
<p>
<tt class="FUNCTION">
gnome_config_init_iterator_sections()</tt> allows you
to iterate over the sections in a file, rather than
over the keys in a section. When iterating over
sections, <tt class="FUNCTION">
gnome_config_iterator_next()</tt> ignores its <span
class="STRUCTNAME">value</span> argument and places the
section name in the <span class="STRUCTNAME">key</span>
argument.
</p>
<div class="FIGURE">
<a name="STARTUP-GNOMECONFIGITERATORS"></a>
<div class="FUNCSYNOPSIS">
<a name="STARTUP-GNOMECONFIGITERATORS.SYNOPSIS"></a>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="FUNCSYNOPSISINFO">
#include <libgnome/gnome-config.h>
</pre>
</td>
</tr>
</table>
<p>
<code><code class="FUNCDEF">void* <tt class=
"FUNCTION">
gnome_config_init_iterator</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void* <tt class=
"FUNCTION">
gnome_config_private_init_iterator</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void* <tt class=
"FUNCTION">
gnome_config_init_iterator_sections</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void* <tt class=
"FUNCTION">
gnome_config_private_init_iterator_sections</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void* <tt class=
"FUNCTION">
gnome_config_iterator_next</tt></code>(void* <tt
class="PARAMETER"><i>iterator_handle</i></tt>,
gchar** <tt class="PARAMETER"><i>key</i></tt>,
gchar** <tt class="PARAMETER"><i>
value</i></tt>);</code>
</p>
</div>
<p>
<b>Figure 6. Configuration file iterators</b>
</p>
</div>
</div>
<div class="SECT3">
<h3 class="SECT3">
<a name="Z85">Other Config File Operations</a>
</h3>
<p>
<a href="z79.html#STARTUP-GNOMECONFIGMISC">Figure 7</a>
lists some additional operations available for
manipulating config files. The most important of these
have already been mentioned in passing. <tt class=
"FUNCTION">gnome_config_sync()</tt> writes the
configuration file to disk, and <tt class="FUNCTION">
gnome_config_push_prefix()</tt> allows you to shorten
the path passed to the other <tt class="APPLICATION">
gnome-config</tt> functions. There are also boolean
tests, to ask <tt class="APPLICATION">gnome-config</tt>
whether a given section exists.
</p>
<p>
Two new operations are introduced: to <i class=
"FIRSTTERM">drop</i> a file or section means to forget
any information about it stored in memory, including
cached values loaded from the file and values not yet
saved to the file with <tt class="FUNCTION">
gnome_config_sync()</tt>. To <i class="FIRSTTERM">
clean</i> a file, section, or key means to unset its
value(s), so the file, section, or key will not exist
once <tt class="FUNCTION">gnome_config_sync()</tt> is
called.
</p>
<p>
<tt class="FUNCTION">gnome_config_sync()</tt>
automatically calls <tt class="FUNCTION">
gnome_config_drop_all()</tt> to free all <tt class=
"APPLICATION">gnome-config</tt> resources, since the
information is safely stored on disk.
</p>
<p>
Functions are also provided to get the "real"
(filesystem) path of a configuration file from a <tt
class="APPLICATION">gnome-config</tt> path. These are
unlikely to be useful in application code.
</p>
<div class="FIGURE">
<a name="STARTUP-GNOMECONFIGMISC"></a>
<div class="FUNCSYNOPSIS">
<a name="STARTUP-GNOMECONFIGMISC.SYNOPSIS"></a>
<table border="0" bgcolor="#E0E0E0" width="100%">
<tr>
<td>
<pre class="FUNCSYNOPSISINFO">
#include <libgnome/gnome-config.h>
</pre>
</td>
</tr>
</table>
<p>
<code><code class="FUNCDEF">gboolean <tt class=
"FUNCTION">
gnome_config_has_section</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gboolean <tt class=
"FUNCTION">
gnome_config_private_has_section</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_drop_all</tt></code>(void);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_sync</tt></code>(void);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_sync_file</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_sync_file</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_drop_file</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_drop_file</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_clean_file</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_clean_file</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_clean_section</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_clean_section</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">gnome_config_clean_key</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_private_clean_key</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_get_real_path</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">gchar* <tt class=
"FUNCTION">
gnome_config_private_get_real_path</tt></code>(const
gchar* <tt class="PARAMETER"><i>
path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_push_prefix</tt></code>(const gchar*
<tt class="PARAMETER"><i>path</i></tt>);</code>
</p>
<p>
<code><code class="FUNCDEF">void <tt class=
"FUNCTION">
gnome_config_pop_prefix</tt></code>(void);</code>
</p>
</div>
<p>
<b>Figure 7. Miscellaneous configuration file
functions</b>
</p>
</div>
</div>
</div>
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