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>.