diff options
Diffstat (limited to 'lib/stdlib/doc/src')
| -rw-r--r-- | lib/stdlib/doc/src/sys.xml | 85 |
1 files changed, 77 insertions, 8 deletions
diff --git a/lib/stdlib/doc/src/sys.xml b/lib/stdlib/doc/src/sys.xml index 073faf2df2..a177b80739 100644 --- a/lib/stdlib/doc/src/sys.xml +++ b/lib/stdlib/doc/src/sys.xml @@ -211,18 +211,87 @@ <p>Gets the status of the process.</p> <p>The value of <c><anno>Misc</anno></c> varies for different types of processes. For example, a <c>gen_server</c> process returns - the callback module's state, and a <c>gen_fsm</c> process - returns information such as its current state name. Callback - modules for <c>gen_server</c> and <c>gen_fsm</c> can also - customise the value of <c><anno>Misc</anno></c> by exporting - a <c>format_status/2</c> function that contributes - module-specific information; - see <seealso marker="gen_server#Module:format_status/2">gen_server:format_status/2</seealso> - and <seealso marker="gen_fsm#Module:format_status/2">gen_fsm:format_status/2</seealso> + the callback module's state, a <c>gen_fsm</c> process + returns information such as its current state name and state data, + and a <c>gen_event</c> process returns information about each of its + registered handlers. Callback modules for <c>gen_server</c>, + <c>gen_fsm</c>, and <c>gen_event</c> can also customise the value + of <c><anno>Misc</anno></c> by exporting a <c>format_status/2</c> + function that contributes module-specific information; + see <seealso marker="gen_server#Module:format_status/2">gen_server:format_status/2</seealso>, + <seealso marker="gen_fsm#Module:format_status/2">gen_fsm:format_status/2</seealso>, and + <seealso marker="gen_event#Module:format_status/2">gen_event:format_status/2</seealso> for more details.</p> </desc> </func> <func> + <name name="get_state" arity="1"/> + <name name="get_state" arity="2"/> + <fsummary>Get the state of the process</fsummary> + <desc> + <p>Gets the state of the process.</p> + <note> + <p>These functions are intended only to help with debugging. They are provided for + convenience, allowing developers to avoid having to create their own state extraction + functions and also avoid having to interactively extract state from the return values of + <c><seealso marker="get_status/1">get_status/1</seealso></c> or + <c><seealso marker="get_status/2">get_status/2</seealso></c> while debugging.</p> + </note> + <p>The value of <c><anno>State</anno></c> varies for different types of + processes. For a <c>gen_server</c> process, the returned <c><anno>State</anno></c> + is simply the callback module's state. For a <c>gen_fsm</c> process, + <c><anno>State</anno></c> is the tuple <c>{CurrentStateName, CurrentStateData}</c>. + For a <c>gen_event</c> process, <c><anno>State</anno></c> a list of tuples, + where each tuple corresponds to an event handler registered in the process and contains + <c>{Module, Id, HandlerState}</c>, where <c>Module</c> is the event handler's module name, + <c>Id</c> is the handler's ID (which is the value <c>false</c> if it was registered without + an ID), and <c>HandlerState</c> is the handler's state.</p> + <p>To obtain more information about a process, including its state, see + <seealso marker="get_status/1">get_status/1</seealso> and + <seealso marker="get_status/2">get_status/2</seealso>.</p> + </desc> + </func> + <func> + <name name="replace_state" arity="2"/> + <name name="replace_state" arity="3"/> + <fsummary>Replace the state of the process</fsummary> + <desc> + <p>Replaces the state of the process, and returns the new state.</p> + <note> + <p>These functions are intended only to help with debugging, and they should not be + be called from normal code. They are provided for convenience, allowing developers + to avoid having to create their own custom state replacement functions.</p> + </note> + <p>The <c><anno>StateFun</anno></c> function provides a new state for the process. + The <c><anno>State</anno></c> argument and <c><anno>NewState</anno></c> return value + of <c><anno>StateFun</anno></c> vary for different types of processes. For a + <c>gen_server</c> process, <c><anno>State</anno></c> is simply the callback module's + state, and <c><anno>NewState</anno></c> is a new instance of that state. For a + <c>gen_fsm</c> process, <c><anno>State</anno></c> is the tuple + <c>{CurrentStateName, CurrentStateData}</c>, and <c><anno>NewState</anno></c> + is a similar tuple that may contain a new state name, new state data, or both. + For a <c>gen_event</c> process, <c><anno>State</anno></c> is the tuple + <c>{Module, Id, HandlerState}</c> where <c>Module</c> is the event handler's module name, + <c>Id</c> is the handler's ID (which is the value <c>false</c> if it was registered without + an ID), and <c>HandlerState</c> is the handler's state. <c><anno>NewState</anno></c> is a + similar tuple where <c>Module</c> and <c>Id</c> shall have the same values as in + <c><anno>State</anno></c> but the value of <c>HandlerState</c> may be different. Returning + a <c><anno>NewState</anno></c> whose <c>Module</c> or <c>Id</c> values differ from those of + <c><anno>State</anno></c> will result in the event handler's state remaining unchanged. For a + <c>gen_event</c> process, <c><anno>StateFun</anno></c> is called once for each event handler + registered in the <c>gen_event</c> process.</p> + <p>If a <c><anno>StateFun</anno></c> function decides not to effect any change in process + state, then regardless of process type, it may simply return its <c><anno>State</anno></c> + argument.</p> + <p>If a <c><anno>StateFun</anno></c> function crashes or throws an exception, then + for <c>gen_server</c> and <c>gen_fsm</c> processes, the original state of the process is + unchanged. For <c>gen_event</c> processes, a crashing or failing <c><anno>StateFun</anno></c> + function means that only the state of the particular event handler it was working on when it + failed or crashed is unchanged; it can still succeed in changing the states of other event + handlers registered in the same <c>gen_event</c> process.</p> + </desc> + </func> + <func> <name name="install" arity="2"/> <name name="install" arity="3"/> <fsummary>Install a debug function in the process</fsummary> |