---
name: "zmq_msg_copy"
section: "3"
platform: "linux"
package: "zeromq"
version: "4.3.5-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/zmq_msg_copy"
---

# zmq\_msg\_copy(3)

copy content of a message to another message

## 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

[**zmq\_msg\_move**(3)](/zmq_msg_move/3.md) [**zmq\_msg\_init**(3)](/zmq_msg_init/3.md) [**zmq\_msg\_init\_size**(3)](/zmq_msg_init_size/3.md) [**zmq\_msg\_init\_buffer**(3)](/zmq_msg_init_buffer/3.md) [**zmq\_msg\_init\_data**(3)](/zmq_msg_init_data/3.md) [**zmq\_msg\_close**(3)](/zmq_msg_close/3.md) [**zmq**(7)](/zmq/7.md)

## AUTHORS

This page was written by the 0MQ community. To make a change please read the 0MQ Contribution Policy at **http://www.zeromq.org/docs:contributing**.