NAME

       unbuffer - unbuffer output

SYNOPSIS

       unbuffer program [ args ]

INTRODUCTION

       unbuffer disables the output buffering that occurs when program output is redirected from non-interactive
       programs.  For example, suppose you are watching the output from a fifo by running it through od and then
       more.

            od -c /tmp/fifo | more

       You will not see anything until a full page of output has been produced.

       You can disable this automatic buffering as follows:

            unbuffer od -c /tmp/fifo | more

       Normally, unbuffer does not read from stdin.  This simplifies use of unbuffer in some situations.  To use
       unbuffer in a pipeline, use the -p flag.  Example:

               process1 | unbuffer -p process2 | process3

CAVEATS

       unbuffer -p may appear to work incorrectly if a process feeding input to unbuffer exits.  Consider:
               process1 | unbuffer -p process2 | process3

       If process1 exits, process2 may not yet have finished.  It is impossible for unbuffer  to  know  long  to
       wait  for  process2  and  process2  may not ever finish, for example, if it is a filter.  For expediency,
       unbuffer simply exits when it encounters an EOF from either its input or process2.

       In order to have a version of unbuffer that worked in all situations, an oracle would be  necessary.   If
       you  want  an  application-specific solution, workarounds or hand-coded Expect may be more suitable.  For
       example, the following example shows how to allow grep to  finish  processing  when  the  cat  before  it
       finishes  first.   Using  cat  to  feed  grep  would never require unbuffer in real life.  It is merely a
       placeholder for some imaginary process that may or may not finish.  Similarly, the final cat at  the  end
       of the pipeline is also a placeholder for another process.

       $ cat /tmp/abcdef.log | grep abc | cat
       abcdef
       xxxabc defxxx
       $ cat /tmp/abcdef.log | unbuffer grep abc | cat
       $ (cat /tmp/abcdef.log ; sleep 1) | unbuffer grep abc | cat
       abcdef
       xxxabc defxxx
       $

BUGS

       The man page is longer than the program.

SEE ALSO

       "Exploring  Expect:  A  Tcl-Based Toolkit for Automating Interactive Programs" by Don Libes, O'Reilly and
       Associates, January 1995.

AUTHOR

       Don Libes, National Institute of Standards and Technology

                                                   1 June 1994                                       UNBUFFER(1)