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Connect to a netgraph node.

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


The nghook utility creates a ng_socket 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:

Option Description
-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. (Not supported by INtime)
-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.


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.


INtime 4.0

See Also

ngctl, ng_socket, netgraph