# sd_event_source_set_enabled

## NAME



           sd_event_source_set_enabled, sd_event_source_get_enabled,
           SD_EVENT_ON, SD_EVENT_OFF, SD_EVENT_ONESHOT - Enable or disable
           event sources
    


## SYNOPSIS



           **#include <systemd/sd-event.h>**
    
           **enum {**
                   **SD_EVENT_OFF** = 0,
                   **SD_EVENT_ON** = 1,
                   **SD_EVENT_ONESHOT** = -1,
           };
    
           **int sd_event_source_set_enabled(sd_event_source ***_source_**,**
                                           **int** _enabled_**);**
    
           **int sd_event_source_get_enabled(sd_event_source ***_source_**,**
                                           **int ***_ret_**);**
    


## DESCRIPTION



           **sd_event_source_set_enabled()** may be used to enable or disable the
           event source object specified as _source_. The _enabled_ parameter
           takes one of **SD_EVENT_ON**(to enable), **SD_EVENT_OFF**(to disable) or
           **SD_EVENT_ONESHOT**. If invoked with **SD_EVENT_ONESHOT** the event
           source will be enabled but automatically reset to **SD_EVENT_OFF**
           after one dispatch. For **SD_EVENT_OFF** , the event source _source_ may
           be **NULL** , in which case the function does nothing. Otherwise,
           _source_ must be a valid pointer to an sd_event_source object.
    
           Event sources that are disabled will not result in event loop
           wakeups and will not be dispatched, until they are enabled again.
    
           **sd_event_source_get_enabled()** may be used to query whether the
           event source object _source_ is currently enabled or not. If both
           the _source_ and the output parameter _ret_ are **NULL** , this function
           returns false. Otherwise, _source_ must be a valid pointer to an
           sd_event_source object. If the output parameter _ret_ is not **NULL** ,
           it is set to the enablement state (one of **SD_EVENT_ON** ,
           **SD_EVENT_OFF** , **SD_EVENT_ONESHOT**). The function also returns true if
           the event source is not disabled.
    
           Event source objects are enabled when they are first created with
           calls such as sd_event_add_io(3), sd_event_add_time(3). However,
           depending on the event source type they are enabled continuously
           (**SD_EVENT_ON**) or only for a single invocation of the event source
           handler (**SD_EVENT_ONESHOT**). For details see the respective manual
           pages.
    
           As event source objects stay active and may be dispatched as long
           as there is at least one reference to them, in many cases it is a
           good idea to combine a call to sd_event_source_unref(3) with a
           prior call to **sd_event_source_set_enabled()** with **SD_EVENT_OFF** , to
           ensure the event source is not dispatched again until all other
           remaining references are dropped.
    


## RETURN VALUE



           On success, **sd_event_source_set_enabled()** returns a non-negative
           integer.  **sd_event_source_get_enabled()** returns zero if the source
           is disabled (**SD_EVENT_OFF**) and a positive integer otherwise. On
           failure, they return a negative errno-style error code.
    
       **Errors**
           Returned errors may indicate the following problems:
    
           **-EINVAL**
               _source_ is not a valid pointer to an sd_event_source object.
    
           **-ENOMEM**
               Not enough memory.
    
           **-ECHILD**
               The event loop has been created in a different process,
               library or module instance.
    


## NOTES



           Functions described here are available as a shared library, which
           can be compiled against and linked to with the
           **libsystemd pkg-config**(1) file.
    
           The code described here uses getenv(3), which is declared to be
           not multi-thread-safe. This means that the code calling the
           functions described here must not call setenv(3) from a parallel
           thread. It is recommended to only do calls to **setenv()** from an
           early phase of the program when no other threads have been
           started.
    


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