4. Threads
To use the POSIX standard thread API (pthreads), link libpthread.so
to your program.
4.1. Thread Creation
Each thread in a process is identified by a thread ID,
pthread_t.
The pthread_self function returns the thread ID of the current
thread.
This thread IDs can be compared with the pthread_equal
function.
if (!pthread_equal (pthread_self (),
other_thread))
pthread_join
(other_thread, NULL);
each thread executes a thread function:
void * function(void *)
The pthread_create function creates a new thread.
A pointer to a pthread_t variable: store the thread ID of
the new thread.
A pointer to a thread attribute object. You can pass NULL
to use the default attributes.
A pointer to the thread function. void* (*) (void*)
A thread argument value of type void*.
Compile and link this program:
% cc -o thread-create thread-create.c
–lpthread
A thread exits in two ways.
return from the thread function. The function return value
is the thread return value.
explicitly call pthread_exit. The argument to pthread_exit
is the thread’s return value.
Create a Thread
#include <pthread.h>
#include <stdio.h>
/* Prints x’s to stderr. The parameter is
unused. Does not return. */
void* print_xs (void* unused)
{
while (1)
fputc (‘x’, stderr);
return NULL;
}
/* The main program. */
int main ()
{
pthread_t thread_id;
/* Create a new thread. The new thread will run the print_xs function.
*/
pthread_create (&thread_id, NULL, &print_xs, NULL);
/* Print o’s continuously to stderr. */
while (1)
fputc (‘o’, stderr);
return 0;
}
4.1.1. Passing Data to Threads
Listing 4.2 (thread-create2) Create Two
Threads
#include <pthread.h&g
