Creating a Default Thread

When an attribute object is not specified, the object is NULL, and the default thread is created with the following attributes:

• Process scope

• Nondetached

• A default stack and stack size

• A priority of zero

You can also create a default attribute object with pthread_attr_init() , and then use this attribute object to create a default thread. See the section Initializing Attributes for details.

pthread_create Syntax

Use pthread_create(3C) to add a new thread of control to the current process.

int pthread_create(pthread_t *restrict tid, const pthread_attr_t 
    *restrict tattr, void*(*start_routine)(void *), void *restrict arg);

#include <pthread.h>

pthread_attr_t() tattr;
pthread_t tid;
extern void *start_routine(void *arg);
void *arg;
int ret; 

/* default behavior*/
ret = pthread_create(&tid, NULL, start_routine, arg);

/* initialized with default attributes */
ret = pthread_attr_init(&tattr);
/* default behavior specified*/
ret = pthread_create(&tid, &tattr, start_routine, arg);

The pthread_create() function is called with attr that has the necessary state behavior. start_routine is the function with which the new thread begins execution. When start_routine returns, the thread exits with the exit status set to the value returned by start_routine. See pthread_create Syntax.

When pthread_create() is successful, the ID of the created thread is stored in the location referred to as tid.

When you call pthread_create() with either a NULL attribute argument or a default attribute, pthread_create() creates a default thread. When tattr is initialized, the thread acquires the default behavior.

pthread_create Return Values

pthread_create() returns zero when the call completes successfully. Any other return value indicates that an error occurred. When any of the following conditions are detected, pthread_create() fails and returns the corresponding value.

EAGAIN

Description:

A system limit is exceeded, such as when too many threads have been created.

EINVAL

Description:

The value of tattr is invalid.

EPERM

Description:

The caller does not have appropriate permission to set the required scheduling parameters or scheduling policy.