1UNBUFFER(1)                 General Commands Manual                UNBUFFER(1)
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NAME

6       unbuffer - unbuffer output
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SYNOPSIS

9       unbuffer program [ args ]
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INTRODUCTION

12       unbuffer  disables the output buffering that occurs when program output
13       is redirected.  For example, suppose you are watching the output from a
14       fifo by running it through od and then more.
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16            od -c /tmp/fifo | more
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18       You  will  not  see  anything until a full page of output has been pro‐
19       duced.
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21       You can disable this automatic buffering as follows:
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24            unbuffer od -c /tmp/fifo | more
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26       Normally, unbuffer does not read from stdin.  This  simplifies  use  of
27       unbuffer in some situations.  To use unbuffer in a pipeline, use the -p
28       flag.  Example:
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30               process1 | unbuffer -p process2 | process3
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CAVEATS

33       unbuffer -p may appear to work incorrectly if a process  feeding  input
34       to unbuffer exits.  Consider:
35               process1 | unbuffer -p process2 | process3
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37       If  process1 exits, process2 may not yet have finished.  It is impossi‐
38       ble for unbuffer to know long to wait for process2 and process2 may not
39       ever  finish, for example, if it is a filter.  For expediency, unbuffer
40       simply exits when it  encounters  an  EOF  from  either  its  input  or
41       process2.
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43       In  order  to have a version of unbuffer that worked in all situations,
44       an oracle would be necessary.   If  you  want  an  application-specific
45       solution,  workarounds  or hand-coded Expect may be more suitable.  For
46       example, the following example shows how to allow grep to  finish  pro‐
47       cessing  when the cat before it finishes first.  Using cat to feed grep
48       would never require unbuffer in real life.  It is merely a  placeholder
49       for  some imaginary process that may or may not finish.  Similarly, the
50       final cat at the end of the pipeline is also a placeholder for  another
51       process.
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54       $ cat /tmp/abcdef.log | grep abc | cat
55       abcdef
56       xxxabc defxxx
57       $ cat /tmp/abcdef.log | unbuffer grep abc | cat
58       $ (cat /tmp/abcdef.log ; sleep 1) | unbuffer grep abc | cat
59       abcdef
60       xxxabc defxxx
61       $
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BUGS

64       The man page is longer than the program.
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SEE ALSO

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

72       Don Libes, National Institute of Standards and Technology
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76                                  1 June 1994                      UNBUFFER(1)