NAME

pthread_mutex_trylock − Attempts to lock the specified mutex, without waiting if already locked

SYNOPSIS

#include <pthread.h>
int pthread_mutex_trylock(
        pthread_mutex_t ∗mutex );

LIBRARY

DECthreads POSIX 1003.1c Library (libpthread.so)

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

IEEE Std 1003.1c-1995, POSIX System Application Program Interface

PARAMETERS

mutex
Mutex to be locked.

DESCRIPTION

This routine attempts to lock the mutex specified in the mutex argument. When a thread calls this routine, an attempt is made to immediately lock the mutex. If the mutex is successfully locked, this routine returns zero (0) and the calling thread becomes the mutex’s current owner. If the specified mutex is locked when a thread calls this routine, the calling thread does not wait for the mutex to become available. 

The behavior of this routine is as follows:

       •For a normal, default, or errorcheck mutex: if the mutex is locked by any thread (including the calling thread) when this routine is called, this routine returns [EBUSY] and the calling thread does not wait to acquire the lock. 

       •For a normal or errorcheck mutex: if the mutex is not owned, this routine returns zero (0) and the mutex becomes locked by the calling thread. 

       •For a recursive mutex: if the mutex is owned by the calling thread, this routine returns zero (0) and the mutex lock count is incremented.  (To unlock a recursive mutex, each call to pthread_mutex_trylock(3) must be matched by a call to pthread_mutex_unlock(3).) 

Use the pthread_mutexattr_settype(3) routine to set the mutex type attribute (normal, default, recursive, or errorcheck). 

RETURN VALUES

If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows:

0Successful completion. 

[EBUSY]
The mutex is already locked; therefore, it was not acquired.

[EINVAL]
The value specified by mutex is not a valid mutex. 

ERRORS

None

SEE ALSO

Functions: pthread_mutexattr_settype(3), pthread_mutex_destroy(3), pthread_mutex_init(3), pthread_mutex_lock(3), pthread_mutex_unlock(3)

Manuals: Guide to DECthreads and Programmer’s Guide