Name

pthread_create − Creates a thread object and thread. 

Syntax

#include <pthread.h>

int pthread_create (thread, attr, start_routine, arg)
pthread_t *thread;
pthread_attr_t attr;
pthread_startroutine_t start_routine;
pthread_addr_t arg;

Arguments

thread Thread object created. 

attr Thread attributes object that defines the characteristics of the thread being created. If you specify pthread_attr_default, default attributes are used. 

start_routine
Function executed as the new thread’s start routine.

arg Address value copied and passed to the thread’s start routine. 

Description

This routine creates a thread object and a thread.  A thread is a single, sequential flow of control within a program. It is the active execution of a designated routine, including any nested routine invocations. A thread object defines and controls the executing thread. 

Calling this routine sets into motion the following actions:

•An internal thread object is created to describe the thread. 

•The associated executable thread is created with attributes specified by the attr argument (or with default attributes if pthread_attr_default is specified). 

•The thread argument receives the new thread. 

•The start_routine function is called when this routine successfully completes. 

The thread is created in the ready state and therefore might immediately begin executing the function specified by the start_routine argument.  The newly created thread will begin running before pthread_create completes if the new thread follows the SCHED_RR or SCHED_FIFO scheduling policy or has a priority higher than the creating thread, or both.  Otherwise, the new thread begins running at its turn, which with sufficient processors, might also be before pthread_create returns. 

The start_routine is passed a copy of the arg argument.  The value of the arg argument is unspecified. 

The thread object exists until the pthread_detach routine is called or the thread terminates, whichever occurs last. 

The synchronization between the caller of pthread_create and the newly created thread is through the use of the pthread_join routine (or any other mutexes or condition variables they agree to use). 

Return Values

If an error condition occurs, no thread is created, the contents of thread are undefined, and this routine returns -1 and sets errno to the corresponding error value.  Possible return values are as follows.