Undefined reference to 'pthread _ create'

As a beginner in Linux, I am only getting started with thread programming. According to an example in the GUN/Linux programming guide, the following error occurs:
Undefined reference to 'pthread _ create'
Undefined reference to 'pthread _ join'

Cause:
The pthread library is not the default library in Linux. You must use the static library libpthread for connection. a, you need to link to this library when using pthread_create () to create a thread and calling the pthread_atfork () function to create a fork handler.

Solution:
Add the-lpthread parameter to the compilation.
Gcc thread. c-o thread-lpthread
Thread. c is your source file. Do not forget to add the header file # include <pthread. h>

In addition, the # include <stdlib. h>

From the column andy572633