---
name: "nghook"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/nghook"
---

# nghook(8)

connect to a netgraph node

## NAME

**nghook** – connect to a netgraph node

## SYNOPSIS

**nghook** \[**-adlnSs**\] \[**-m** *msg*\] *path* \[*hookname*\]

**nghook** **-e** \[**-n**\] \[**-m** *msg*\] *path* *hookname* *program* \[*args* *...*\]

## DESCRIPTION

The **nghook** utility creates a [ng\_socket(4)](/ng_socket/4.md) socket type node and connects it to hook *hookname* of the node found at *path*. If *hookname* is omitted, “debug” is assumed.

If the **-e** option is given, the third argument is interpreted as the path to a program, and this program is executed with the remaining arguments as its arguments. Before executing, the program Netgraph messages (specified by the **-m** option) are sent to the node. The program is executed with its standard input (unless closed by **-n**) and output connected to the hook.

If the **-e** option is not given, all data written to standard input is sent to the node, and all data received from the node is relayed to standard output. Messages specified with **-m** are sent to the node before the loop is entered. The **nghook** utility exits when EOF is detected on standard input in this case.

The options are as follows:

- **-a**

  Output each packet read in human-readable decoded ASCII form instead of raw binary.

- **-d**

  Increase the debugging verbosity level.

- **-e**

  Execute the program specified by the third argument.

- **-l**

  Loops all received data back to the hook in addition to writing it to standard output.

- **-m** *msg*

  Before executing the program (in **-e** mode) send the given ASCII control message to the node. This option may be given more than once.

- **-n**

  Do not attempt to read any data from standard input. The **nghook** utility will continue reading from the node until stopped by a signal.

- **-S**

  Use file descriptor 0 for output instead of the default 1.

- **-s**

  Use file descriptor 1 for input instead of the default 0.

## SEE ALSO

[netgraph(3)](/netgraph/3.md), [netgraph(4)](/netgraph/4.md), [ngctl(8)](/ngctl/8.md)

## HISTORY

The **netgraph** system was designed and first implemented at Whistle Communications, Inc. in a version of FreeBSD 2.2 customized for the Whistle InterJet.

## AUTHORS

Archie Cobbs ⟨*archie@whistle.com*⟩

## BUGS

Although all input is read in unbuffered mode, there is no way to control the packetization of the input.

If the node sends a response to a message (specified by **-m**), this response is lost.