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Updated: Wednesday, February 9, 2022
 
 

unbuffer (1)

Name

unbuffer - unbuffer output

Synopsis

unbuffer program [ args ]

Description

UNBUFFER(1)                 General Commands Manual                UNBUFFER(1)



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  pro-
       duced.

       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  impossi-
       ble 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 pro-
       cessing 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.



ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | shell/expect     |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+

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

AUTHOR
       Don Libes, National Institute of Standards and Technology



NOTES
       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source        was        downloaded        from         https://source-
       forge.net/projects/expect/files/Expect/5.45/expect5.45.tar.gz/download.

       Further information about this software can be found on the open source
       community website at https://core.tcl.tk/expect/.



                                  1 June 1994                      UNBUFFER(1)