multitee(1)						      General Commands Manual						       multitee(1)

NAME

       multitee - send multiple inputs to multiple outputs

SYNTAX

       multitee [ -bsize ] [ -vQq ] [ fd-fd,fd,fd...  ] ...

DESCRIPTION

       multitee  sends	multiple  inputs  to multiple outputs.	Given an argument of the form fdin-fdout,fdout,fdout...  it will send all input on
       file descriptor fdin to each descriptor fdout.  It will exit when all fdin are closed.  Several arguments may specify outputs from the same
       fdin.

       -fdout  and  ,fdout are equivalent.  If there is an error of any sort (including SIGPIPE) in writing to fdout, multitee prints a warning on
       stderr and forgets fdout entirely.  (This doesn't affect reads on fdin.)  If -fdout is replaced by :fdout then multitee will exit upon  any
       SIGPIPEs from that descriptor.

       Furthermore, efd means that as soon as fdin reaches end of file, fd is considered to reach EOF as well.	multitee will warn about any input
       errors and then treat them like EOF.

       Unlike tee, multitee tries its best to continue processing all descriptors even while some of them are blocked. However, it will get  stuck
       reading	if  someone else is reading the descriptor and grabs the input first; it will get stuck writing if an input packet does not fit in
       an output pipe.	(If the output descriptor has NDELAY set, and multitee receives EWOULDBLOCK, it writes one byte at a time  to  avoid  pipe
       synchronization	problems.)  While it is tempting to set the descriptors to non-blocking mode, this is dangerous: other processes using the
       same open file may not be able to deal with NDELAY.  It is incredible that none of the major UNIX vendors or standards committees has  come
       up  with true per-process non-blocking I/O.  (Under BSD 4.3 and its variants, multitee could send timer signals to itself rapidly to inter-
       rupt any blocking I/O. However, this cannot work under BSD 4.2, and is generally more trouble than it's worth.)	A program can  set  NDELAY
       before invoking multitee if it knows that no other processes will use the same open file.

       multitee  will also temporarily stop reading an input descriptor if more than 8192 bytes are pending on one of its output descriptors. This
       does not affect independent fdin-fdout pairs.

       multitee has several flags:

       -bsize	   Change input buffer size from 8192 to size.	Unlike the previous version of multitee, this version does not require output buf-
		   fers, and does not copy bytes anywhere between read() and write().

       -v	   Verbose.

       -q	   Quiet.  multitee will not use stderr in any way (except, of course, if descriptor 2 is specified in an argument).

       -Q	   Normal level of verbosity.

EXIT VALUE

       0 normally.  1 for usage messages.  3 if multitee runs out of memory.  4 in various impossible situations.

DIAGNOSTICS

       fatal: out of memory
	      multitee has run out of memory.

       warning: cannot read descriptor
	      Self-explanatory.

       warning: cannot write descriptor
	      Self-explanatory.

EXAMPLES

       multitee 0-1,4,5 4>foo 5>bar

       Same as tee foo bar except for better blocking behavior.

       multitee 0:1 3:1 4:1,2 6:7

       Merge several sources into the output, meanwhile copying 6 to 7 and recording 4's input in 2.

       tcpclient servermachine smtp multitee 0:7 6:1e0

       Same as mconnect on Suns.  The e0 tells multitee to quit as soon as the network connection closes.

RESTRICTIONS

       multitee  expects all descriptors involved to be open.  Currently a closed descriptor acts like an open descriptor which can never be writ-
       ten to.

BUGS

       None known.

VERSION

       multitee version 3.0, 7/22/91.

AUTHOR

       Placed into the public domain by Daniel J. Bernstein.

SEE ALSO

       tee(1)

																       multitee(1)