= zmq_ctx_get_ext(3)


== NAME

zmq_ctx_get_ext - get extended context options


== SYNOPSIS
*int zmq_ctx_get_ext (void '*context', int 'option_name', void '*option_value', size_t '*option_len');*


== DESCRIPTION
The _zmq_ctx_get()_ function shall retrieve the value for the option
specified by the 'option_name' argument and store it in the buffer pointed to
by the 'option_value' argument. 
The 'option_len' argument is the size in bytes of the buffer pointed
to by 'option_value'; upon successful completion _zmq_ctx_get_ext()_ shall
modify the 'option_len' argument to indicate the actual size of the option
value stored in the buffer.

The _zmq_ctx_get_ext()_ function accepts all the option names accepted by
_zmq_ctx_get()_.
Options that make most sense to retrieve using _zmq_ctx_get_ext()_ instead of
_zmq_ctx_get()_ are:

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

[horizontal]
Option value type:: character string
Option value unit:: N/A
Default value:: empty string


== RETURN VALUE
The _zmq_ctx_get_ext()_ 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 prefix on internal ZMQ thread names:
----
void *context = zmq_ctx_new ();
const char prefix[] = "MyApp";
size_t prefixLen = sizeof(prefix);
zmq_ctx_set (context, ZMQ_THREAD_NAME_PREFIX, &prefix, &prefixLen);

char buff[256];
size_t buffLen = sizeof(buff);
int rc = zmq_ctx_get (context, ZMQ_THREAD_NAME_PREFIX, &buff, &buffLen);
assert (rc == 0);
assert (buffLen == prefixLen);

----


== SEE ALSO
* xref:zmq_ctx_get.adoc[zmq_ctx_get]
* 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/>.
