---
title: mbuf_copym
framework: Kernel
role: symbol
role_heading: Function
platforms: [macOS 10.4+]
path: kernel/1535750-mbuf_copym
---

# mbuf_copym

## Declaration

```occ
errno_t mbuf_copym(const mbuf_t src, size_t offset, size_t len, mbuf_how_t how, mbuf_t *new_mbuf);
```

## Parameters

- `src`: The source mbuf.
- `offset`: The offset in the mbuf to start copying from.
- `len`: The the number of bytes to copy.
- `how`: To block or not to block, that is a question.
- `new_mbuf`: Upon success, the newly allocated mbuf.

## Return Value

Return Value 0 upon success otherwise the errno error.

## Discussion

Discussion Copies len bytes from offset from src to a new mbuf. If the original mbuf contains a packet header, the new mbuf will contain similar packet header except for any tags which may be associated with the original mbuf. mbuf_dup() should be used instead if tags are to be copied to the new mbuf.