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103 lines
3.2 KiB
Groff
103 lines
3.2 KiB
Groff
.\" Copyright (c) 2012 Jeremie Le Hen <jlh@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code and documentation must retain the above
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.\" copyright notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 28, 2012
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.Dt LIBSTDBUF 3
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.Os
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.Sh NAME
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.Nm libstdbuf
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.Nd preloaded library to change standard streams initial buffering
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.Sh DESCRIPTION
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The
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.Nm
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library is meant to be preloaded with the
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.Ev LD_PRELOAD
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environment variable to as to change the initial buffering
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of standard input, standard output and standard error streams.
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.Pp
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Although you may load and configure this library manually,
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an utility,
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.Xr stdbuf 1 ,
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can be used to run a command with the appropriate environment variables.
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.Sh ENVIRONMENT
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Each stream can be configured independently through the following
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environment variables (values are defined below):
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.Bl -tag -width size -offset indent
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.It Ev _STDBUF_I
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Initial buffering definition for the standard input stream
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.It Ev _STDBUF_O
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Initial buffering definition for the standard output stream
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.It Ev _STDBUF_E
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Initial buffering definition for the standard error stream
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.El
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.Pp
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Each variable may take one of the following values:
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.Bl -tag -width size -offset indent
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.It Qq 0
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unbuffered
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.It Qq L
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line buffered
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.It Qq B
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fully buffered with the default buffer size
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.It Ar size
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fully buffered with a buffer of
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.Ar size
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bytes (suffixes 'k', 'M' and 'G' are accepted)
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.El
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.Sh EXAMPLE
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In the following example, the stdout stream of the
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.Xr awk 1
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command
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will be fully buffered by default because it does not refer
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to a terminal.
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.Nm
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is used to force it to be line-buffered so
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.Xr vmstat 8 Ns 's
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output will not stall until the full buffer fills.
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.Bd -literal -offset indent
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# vmstat 1 | LD_PRELOAD=/usr/lib/libstdbuf.so \\
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STDBUF_1=L awk '$2 > 1 || $3 > 1' | cat -n
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.Ed
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.Pp
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See also the manpage of
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.Xr stdbuf 1
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for a simpler way to do this.
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.Sh HISTORY
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The
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.Nm
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library first appeared in
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.Fx 8.4 .
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.Sh AUTHORS
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.An -nosplit
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The original idea of the
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.Nm
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command comes from
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.An Padraig Brady
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who implemented it in the GNU coreutils.
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.An Jeremie Le Hen
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implemented it on
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.Fx .
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