NAME
dpipe - bi-directional pipe command
SYNOPSIS
dpipe [ OPTIONS ] command [ args ] = command [ args ] [ = [ command [ args ] ] ] ...
DESCRIPTION
dpipe is
a general tool to run two commands diverting the standard
output of the first command into the standard input of the
second and vice-versa. It is the bi-directional extension of
the | (pipe) syntax used by all the shells. The
= has been chosen as a metaphor of two parallel
communication lines between the commands. It is also
possible to concatenate several tools. Intermediate programs
communicate using standard input and standard output with
the preceding tool and alternate standard input and output
towards the following tool. The number of the file
descriptors is use as alternate standard input and output
can be retrieved from the envirnonment variables
ALTERNATE_STDIN and ALTERNATE_STDOUT using getenv(3)
or getenv(1). If an intermediate tool should process
only the data flowing in one direction use { or
} as suffix for the preceding = and prefix of
the following one.
This tool has been written as a tool for the Virtual
Distributed Ethernet.
OPTIONS
dpipe accepts the following options:
|
-n |
--nowrapproc
create only one process per command, the last one being the parent of all the others (the standard behavior of dpipe is to create a process for dpipe and all the processes running the commands are children of dpipe).
|
-d |
--daemon
run as a daemon.
-p PIDFILE
--pidfile PIDFILE
write the process id of the dpipe process (or the id of the last command if -r) to the file PIDFILE
-P PGRPFILE
--pgrpfile PGRPFILE
write the process group id (negative) including all the processes launched by dpipe to the file PGRPFILE
|
-N |
--nowrapnoclean
Like -n but it does not remove PIDFILE or PGRPFILE. (when -n is used together with -p or -P, dpipe creates a cleanup process to wait for the processes to terminate and remove the files. -N avoids the creation of the cleanup process)
EXAMPLES
dpipe a =
b
processes a and b are bidirectionally connected: stdin of a
is connected to stdout of b and vice-versa
dpipe a = b = c
a and b are connected as above. Alternate stdin of b is
connected to stdout of c and alternate stdout of b to stdin
of c
dpipe a =} b }= c
This is a cycle of pipes: stdout of a is connected to stdin
of b, stdout of b with stdin of c, and stdout of c to stdin
of a
dpipe a =} b }={ c {= d = e
all the notations can be mixed together. this is a -> b
-> d -> c and back to a; alternate ports of d are
connected to e
NOTICE
Virtual Distributed Ethernet is not related in any way with www.vde.com ("Verband der Elektrotechnik, Elektronik und Informationstechnik" i.e. the German "Association for Electrical, Electronic & Information Technologies").
SEE ALSO
vde_switch(1), vde_plug(1), vde_plug2tap(1), vdeq(1). wirefilter(1).
AUTHOR
VDE is a project by Renzo Davoli <renzo [AT] cs.it>.