= zmq_msg_copy(3)


== NAME
zmq_msg_copy - copy content of a message to another message


== SYNOPSIS
*int zmq_msg_copy (zmq_msg_t '*dest', zmq_msg_t '*src');*


== DESCRIPTION
The _zmq_msg_copy()_ function shall copy the message object referenced by 'src'
to the message object referenced by 'dest'. The original content of 'dest', if
any, shall be released. You must initialise 'dest' before copying to it.

CAUTION: The implementation may choose not to physically copy the message
content, rather to share the underlying buffer between 'src' and 'dest'. Avoid
modifying message content after a message has been copied with
_zmq_msg_copy()_, doing so can result in undefined behaviour. If what you need
is an actual hard copy, initialize a new message using _zmq_msg_init_buffer()_
with the message content.

CAUTION: Never access 'zmq_msg_t' members directly, instead always use the
_zmq_msg_ family of functions.


== RETURN VALUE
The _zmq_msg_copy()_ function shall return zero if successful. Otherwise it
shall return `-1` and set 'errno' to one of the values defined below.


== ERRORS
*EFAULT*::
Invalid message.


== EXAMPLE
.Copying a message
----
zmq_msg_t msg;
zmq_msg_init_buffer (&msg, "Hello, World", 12);
zmq_msg_t copy;
zmq_msg_init (&copy);
zmq_msg_copy (&copy, &msg);
...
zmq_msg_close (&copy);
zmq_msg_close (&msg);
----

== SEE ALSO
* xref:zmq_msg_move.adoc[zmq_msg_move]
* xref:zmq_msg_init.adoc[zmq_msg_init]
* xref:zmq_msg_init_size.adoc[zmq_msg_init_size]
* xref:zmq_msg_init_buffer.adoc[zmq_msg_init_buffer]
* xref:zmq_msg_init_data.adoc[zmq_msg_init_data]
* xref:zmq_msg_close.adoc[zmq_msg_close]
* xref:zmq.adoc[zmq]


== AUTHORS
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read the 0MQ Contribution Policy at <https://zeromq.org/how-to-contribute/>.