= zmq_ctx_get(3)


== NAME

zmq_ctx_get - get context options


== SYNOPSIS
*int zmq_ctx_get (void '*context', int 'option_name');*


== DESCRIPTION
The _zmq_ctx_get()_ function shall return the option specified by the
'option_name' argument.

The _zmq_ctx_get()_ function accepts the following option names:


ZMQ_IO_THREADS: Get number of I/O threads
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_IO_THREADS' argument returns the size of the 0MQ thread pool
for this context.


ZMQ_MAX_SOCKETS: Get maximum number of sockets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_MAX_SOCKETS' argument returns the maximum number of sockets
allowed for this context.


ZMQ_MAX_MSGSZ: Get maximum message size
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_MAX_MSGSZ' argument returns the maximum size of a message
allowed for this context. Default value is INT_MAX.


ZMQ_ZERO_COPY_RECV: Get message decoding strategy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_ZERO_COPY_RECV' argument return whether message decoder uses a zero copy
strategy when receiving messages. Default value is 1.
NOTE: in DRAFT state, not yet available in stable releases.


ZMQ_SOCKET_LIMIT: Get largest configurable number of sockets
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_SOCKET_LIMIT' argument returns the largest number of sockets that
xref:zmq_ctx_set.adoc[zmq_ctx_set] will accept.


ZMQ_IPV6: Set IPv6 option
~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_IPV6' argument returns the IPv6 option for the context.


ZMQ_BLOCKY: Get blocky setting
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_BLOCKY' argument returns 1 if the context will block on terminate,
zero if the "block forever on context termination" gambit was disabled by
setting ZMQ_BLOCKY to false on all new contexts.


ZMQ_THREAD_SCHED_POLICY: Get scheduling policy for I/O threads
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_THREAD_SCHED_POLICY' argument returns the scheduling policy for
internal context's thread pool.


ZMQ_THREAD_NAME_PREFIX: Get name prefix for I/O threads
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_THREAD_NAME_PREFIX' argument gets the numeric prefix of each thread
created for the internal context's thread pool.


ZMQ_MSG_T_SIZE: Get the zmq_msg_t size at runtime
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'ZMQ_MSG_T_SIZE' argument returns the size of the zmq_msg_t structure at
runtime, as defined in the include/zmq.h public header.
This is useful for example for FFI bindings that can't simply do a sizeof().


== RETURN VALUE
The _zmq_ctx_get()_ function returns a value of 0 or greater if successful.
Otherwise it returns `-1` and sets 'errno' to one of the values defined
below.


== ERRORS
*EINVAL*::
The requested option _option_name_ is unknown.
*EFAULT*::
The provided 'context' is invalid.


== EXAMPLE
.Setting a limit on the number of sockets
----
void *context = zmq_ctx_new ();
zmq_ctx_set (context, ZMQ_MAX_SOCKETS, 256);
int max_sockets = zmq_ctx_get (context, ZMQ_MAX_SOCKETS);
assert (max_sockets == 256);
----
.Switching off the context deadlock gambit
----
zmq_ctx_set (ctx, ZMQ_BLOCKY, false);
----


== SEE ALSO
* xref:zmq_ctx_set.adoc[zmq_ctx_set]
* xref:zmq.adoc[zmq]


== AUTHORS
This page was written by the 0MQ community. To make a change please
read the 0MQ Contribution Policy at <https://zeromq.org/how-to-contribute/>.
