---
name: "stdbuf"
section: "1"
platform: "linux"
package: "coreutils"
version: "9.12-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/stdbuf"
---

# stdbuf(1)

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

## 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'