unbuffer
(1)
Name
unbuffer - unbuffer output
Synopsis
unbuffer program [ args ]
Description
User Commands UNBUFFER(1)
NAME
unbuffer - unbuffer output
SYNOPSIS
unbuffer program [ args ]
INTRODUCTION
unbuffer disables the output buffering that occurs when pro-
gram 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 simpli-
fies 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
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User Commands UNBUFFER(1)
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(5) 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 Inter-
active Programs" by Don Libes, O'Reilly and Associates, Jan-
uary 1995.
AUTHOR
Don Libes, National Institute of Standards and Technology
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from http://source-
forge.net/projects/expect/files/Expect/5.45/expect5.45.tar.gz/down-
load
Further information about this software can be found on the
open source community website at http://expect.nist.gov/.
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