Help: How-to Read-Only Field

<?php

add_action( 'show_user_profile', 'my_show_extra_profile_fields' );
add_action( 'edit_user_profile', 'my_show_extra_profile_fields' );

function my_show_extra_profile_fields( $user ) { ?>

	<h3>Code Rep Unique</h3>

	<table class="form-table">

		<tr>
			<th><label for="jobpos">Votre Code Rep Unique</label></th>

			<td>
				<input type="text" name="jobpos" id="jobpos" value="<?php echo esc_attr( get_the_author_meta( 'jobpos', $user->ID ) ); ?>" class="regular-text" /><br />
				<span class="description">Ce code est confidentiel et unique pour chacun des reps.</span>
			</td>
		</tr>

	</table>
<?php }

add_action( 'personal_options_update', 'my_save_extra_profile_fields' );
add_action( 'edit_user_profile_update', 'my_save_extra_profile_fields' );

function my_save_extra_profile_fields( $user_id ) {

	if ( !current_user_can( 'edit_user', $user_id ) )
		return false;

	update_usermeta( $user_id, 'jobpos', $_POST['jobpos'] );
}