activate_plugin action-hook . WP 2.9.0

Fires before a plugin is activated.

If a plugin is silently activated (such as during an update), this hook does not fire.

Usage

add_action( 'activate_plugin', 'action_function_name_6401', 10, 2 );
function action_function_name_6401( $plugin, $network_wide ){
	// action...
}

$plugin(string)

Path to the plugin file relative to the plugins directory.

$network_wide(true/false)

Whether to enable the plugin for all sites in the network or just the current site. Multisite only.
Default: false

Where the hook is called

do_action( 'activate_plugin', $plugin, $network_wide );

Where the hook is used (in WP core)