1.\" Copyright (c) 2012 Jeremie Le Hen <jlh@FreeBSD.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code and documentation must retain the above 8.\" copyright notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd January 1, 2021 28.Dt STDBUF 1 29.Os 30.Sh NAME 31.Nm stdbuf 32.Nd change standard streams initial buffering 33.Sh SYNOPSIS 34.Nm 35.Op Fl e Ar bufdef 36.Op Fl i Ar bufdef 37.Op Fl o Ar bufdef 38.Op Ar command Op ... 39.Sh DESCRIPTION 40.Nm 41is used to change the initial buffering of standard input, 42standard output and/or standard error streams for 43.Ar command . 44It relies on 45.Xr libstdbuf 3 46that is preloaded and configured by 47.Nm 48through environment variables. 49.Pp 50The options are as follows: 51.Bl -tag -width Ds 52.It Fl e Ar bufdef 53Set initial buffering of the standard error stream for 54.Ar command 55as defined by 56.Ar bufdef 57.Pq see Sx BUFFER DEFINITION . 58.It Fl i Ar bufdef 59Set initial buffering of the standard input stream for 60.Ar command 61as defined by 62.Ar bufdef 63.Pq see Sx BUFFER DEFINITION . 64.It Fl o Ar bufdef 65Set initial buffering of the standard output stream for 66.Ar command 67as defined by 68.Ar bufdef 69.Pq see Sx BUFFER DEFINITION . 70.El 71.Sh BUFFER DEFINITION 72Buffer definition is the same as in 73.Xr libstdbuf 3 : 74.Bl -tag -width size -offset indent 75.It Qq 0 76unbuffered 77.It Qq L 78line buffered 79.It Qq B 80fully buffered with the default buffer size 81.It Ar size 82fully buffered with a buffer of 83.Ar size 84bytes (suffixes 'k', 'M' and 'G' are accepted) 85.El 86.Sh EXAMPLES 87In the following example, the stdout stream of the 88.Xr awk 1 89command 90will be fully buffered by default because it does not refer 91to a terminal. 92.Nm 93is used to force it to be line-buffered so 94.Xr vmstat 8 Ns 's 95output will not stall until the full buffer fills. 96.Bd -literal -offset indent 97# vmstat 1 | stdbuf -o L awk '$NF > 1' | cat -n 98.Ed 99.Sh SEE ALSO 100.Xr libstdbuf 3 , 101.Xr setvbuf 3 102.Sh HISTORY 103The 104.Nm 105utility first appeared in 106.Fx 8.4 , 107and was imported to 108.Dx 5.9 . 109.Sh AUTHORS 110.An -nosplit 111The original idea of the 112.Nm 113command comes from 114.An Padraig Brady 115who implemented it in the GNU coreutils. 116.An Jeremie Le Hen 117implemented it on 118.Fx . 119