如果在linux系统下man gettid会出现如下信息。希望有帮助
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gettid returns the thread ID of the current process. This is equal to
the process ID (as returned by getpid(2)), unless the process is part
of a thread group (created by specifying the CLONE_THREAD flag to the
clone(2) system call). All processes in the same thread group have the
same PID, but each one has a unique TID.
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