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STDBUF

Section: User Commands (1)
Updated: February 2026
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NAME

stdbuf - Run COMMAND, with modified buffering operations for its standard streams.

SYNOPSIS

stdbuf ,OPTION/... ,COMMAND/

DESCRIPTION

Run COMMAND, with modified buffering operations for its standard streams.

Mandatory arguments to long options are mandatory for short options too.

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#stdbu-i'-i, --input=,MODEX'tty: link'/: adjust standard input stream buffering
X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#stdbu-o'-o, --output=,MODEX'tty: link'/: adjust standard output stream buffering
X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#stdbu-e'-e, --error=,MODEX'tty: link'/: adjust standard error stream buffering
X'tty: link https://www.gnu.org/software/coreutils/stdbuf#stdbu-help'--helpX'tty: link': display this help and exit
X'tty: link https://www.gnu.org/software/coreutils/stdbuf#stdbu-version'--versionX'tty: link': output version information and exit

If MODE is 'L' the corresponding stream will be line buffered. This option is invalid with standard input.

If MODE is '0' the corresponding stream will be unbuffered.

Otherwise MODE is a number which may be followed by one of the following: KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G,T,P,E,Z,Y,R,Q. Binary prefixes can be used, too: KiB=K, MiB=M, and so on. In this case the corresponding stream will be fully buffered with the buffer size set to MODE bytes.

NOTE: If COMMAND adjusts the buffering of its standard streams ('tee' does for example) then that will override corresponding changes by 'stdbuf'. Also some filters (like 'dd' and 'cat' etc.) don't use streams for I/O, and are thus unaffected by 'stdbuf' settings.