stdbuf(1) User Commands stdbuf(1)
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.
-i, --input=MODE
adjust standard input stream buffering
-o, --output=MODE
adjust standard output stream buffering
-e, --error=MODE
adjust standard error stream buffering
--help display this help and exit
--version
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.
Exit status:
125 if the stdbuf command itself fails
126 if COMMAND is found but cannot be invoked
127 if COMMAND cannot be found
- the exit status of COMMAND otherwise
EXAMPLES
tail -f access.log | stdbuf -oL cut -d ' ' -f1 | uniq
This will immediately display unique entries from access.log
BUGS
On GLIBC platforms, specifying a buffer size, i.e., using fully
buffered mode will result in undefined operation.
AUTHOR
Written by Padraig Brady.
REPORTING BUGS
Report bugs to: <bug-coreutils@gnu.org>.
Report any translation bugs to: <https://translationproject.org/team/>.
GNU coreutils home page: <https://www.gnu.org/software/coreutils/>
General help using GNU software: <https://www.gnu.org/gethelp/>
COPYRIGHT
Copyright © 2026 Free Software Foundation, Inc. License GPLv3+: GNU
GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
Full documentation <https://www.gnu.org/software/coreutils/stdbuf>
or available locally via: info '(coreutils) stdbuf invocation'
GNU coreutils 9.12 September 2026 stdbuf(1)
coreutils 9.12 - Generated Wed Sep 23 13:18:58 CDT 2026