thread_property/2

Documentation
- Reference manual
  - Multithreaded applications
    - Monitoring threads
- Packages

Availability:built-in

thread_property(?Id, ?Property)

True if thread Id has Property. Either or both arguments may be unbound, enumerating all relations on backtracking. Calling thread_property/2 does not influence any thread. See also thread_join/2. For threads that have an alias name, this name is returned in Id instead of the opaque thread identifier. Defined properties are:

alias(Alias)

Alias is the alias name of thread Id.

detached(Boolean)

Current detached status of the thread.

id(Integer)

Integer identifier for the thread. Can be used as argument to the thread predicates, but applications must be aware that these references are reused.

status(Status)

Current status of the thread. Status is one of:

running: The thread is running. This is the initial status of a thread. Please note that threads waiting for something are considered running too.
suspended: Only if the thread is an engine (see section 11). Indicates that the engine is currently not associated with an OS thread.
false: The Goal of the thread has been completed and failed.
true: The Goal of the thread has been completed and succeeded.
exited(Term): The Goal of the thread has been terminated using thread_exit/1 with Term as argument. If the underlying native thread has exited (using pthread_exit()) Term is unbound.
exception(Term): The Goal of the thread has been terminated due to an uncaught exception (see throw/1 and catch/3).

engine(Boolean)

If the thread is an engine (see chapter 11), Boolean is true. Otherwise the property is not present.

thread(ThreadId)

If the thread is an engine that is currently attached to a thread, ThreadId is the thread that executes the engine.

size(Bytes)

The amount of memory associated with this thread. This includes the thread structure, its stacks, its default message queue, its clauses in its thread local dynamic predicates (see thread_local/1) and memory used for representing thread-local answer tries (see section 7).

system_thread_id(Integer)

Thread identifier used by the operating system for the calling thread. Not available on all OSes. This is the same as the Prolog flag system_thread_id for the calling thread. Access to the system thread identifier can, on some systems, be used to gain additional control over or information about Prolog threads.

See also thread_statistics/3 to obtain resource usage information and message_queue_property/2 to get the number of queued messages for a thread.