- get or set process-shared attribute
cc –mt [ flag... ] file... –lpthread [ library... ] #include <pthread.h> int pthread_mutexattr_getpshared( const pthread_mutexattr_t *restrict attr, int *restrict pshared);
int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared);
The pthread_mutexattr_getpshared() function obtains the value of the process-shared attribute from the attributes object referenced by attr. The pthread_mutexattr_setpshared() function is used to set the process-shared attribute in an initialized attributes object referenced by attr.
The process-shared attribute is set to PTHREAD_PROCESS_SHARED to permit a mutex to be operated upon by any thread that has access to the memory where the mutex is allocated, even if the mutex is allocated in memory that is shared by multiple processes. If the process-shared attribute is PTHREAD_PROCESS_PRIVATE, the mutex will only be operated upon by threads created within the same process as the thread that initialized the mutex; if threads of differing processes attempt to operate on such a mutex, the behavior is undefined. The default value of the attribute is PTHREAD_PROCESS_PRIVATE.
Upon successful completion, pthread_mutexattr_getpshared() returns 0 and stores the value of the process-shared attribute of attr into the object referenced by the pshared parameter. Otherwise, an error number is returned to indicate the error.
Upon successful completion, pthread_mutexattr_setpshared() returns 0. Otherwise, an error number is returned to indicate the error.
The pthread_mutexattr_getpshared() and pthread_mutexattr_setpshared() functions may fail if:
The value specified by attr is invalid.
The pthread_mutexattr_setpshared() function may fail if:
The new value specified for the attribute is outside the range of legal values for that attribute.
See attributes(5) for descriptions of the following attributes: