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@cs.unibo.it>.