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NGHOOK(8)               FreeBSD System Manager's Manual              NGHOOK(8)

     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 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

     -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 default 1.

     -s      Use file descriptor 1 for input instead of the default 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 InterJet.

     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), this
     response is lost.

FreeBSD 11.0-PRERELEASE        October 24, 2003        FreeBSD 11.0-PRERELEASE


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