pthreadself

pthread_self is a function in the POSIX threads (pthreads) library that returns the thread identifier of the calling thread. The return type is pthread_t, an opaque value that uniquely identifies a thread within the calling process. The identifier remains valid for the lifetime of the thread, and can be used with other pthreads routines that accept a pthread_t argument. The function is thread-safe and does not require extra synchronization.

Because the pthread_t type is opaque, it should not be interpreted as a number. To compare thread identifiers, portable code should use pthread_equal rather than comparing the values directly. For example, to check if two threads are the same, obtain their IDs (one may come from pthread_self) and compare them with pthread_equal. The result of pthread_self can be supplied to a wide range of pthreads functions that require a thread identifier, such as those that query or manipulate thread state, cancel a thread, or join a thread, provided the target function is specified by the implementation and the thread’s state allows the operation.

Notes and portability: pthread_self is defined by the POSIX standard and is available on systems implementing pthreads. The exact representation of pthread_t is implementation-defined, so code should treat it as an opaque type and rely on pthread_equal for comparisons. Some debuggers or logs may attempt to print the value, but printing pthread_t is not portable and should be avoided in production code. In typical usage, pthread_self helps a thread obtain its own identity for logging, per-thread data management, or coordination tasks within a multi-threaded process.