nghook - connect to a netgraph(4) node


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


The nghook utility creates a ng_socket(4) 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 remain
ing 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
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 be
fore 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
-n Do not attempt to read any data from standard input.
The nghook
utility will continue reading from the node until
stopped by a
-S Use file descriptor 0 for output instead of the de
fault 1.
-s Use file descriptor 1 for input instead of the de
fault 0.


netgraph(3), netgraph(4), ngctl(8)


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


Archie Cobbs <>


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),
response is lost.
BSD October 24, 2003
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