STDBUF

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

stdbuf OPTION... COMMAND

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. 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 e.g.) then that will override corresponding settings changed by ‘stdbuf’. Also some filters (like ‘dd’ and ‘cat’ etc.) don’t use streams for I/O, and are thus unaffected by ‘stdbuf’ settings.

tail -f access.log | stdbuf -oL cut -d ' ' -f1 | uniq
This will immedidately display unique entries from access.log

On GLIBC platforms, specifying a buffer size, i.e. using fully buffered mode will result in undefined operation.

Written by Padraig Brady.

Report stdbuf bugs to bug−coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report stdbuf translation bugs to <http://translationproject.org/team/>

Copyright © 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://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.

The full documentation for stdbuf is maintained as a Texinfo manual. If the info and stdbuf programs are properly installed at your site, the command

info coreutils 'stdbuf invocation'

should give you access to the complete manual.