STDBUF(1)

📦
version 9.12 · 25 versions
, in arch rolling

💖 STDBUF(1) — like, the manual page but make it slay 💖

okay bestie, gather round, because this one is genuinely iconic. it's stdbuf, a User Command, and it's about to fix your buffering problems. yes, buffering. stay with me. 🦋

✨ NAME ✨

stdbuf — run COMMAND, with modified buffering operations for its standard streams. no cap, that's the whole gig. 👑

🌸 SYNOPSIS 🌸

stdbuf OPTION... COMMAND

💅 DESCRIPTION 💅

so basically: you run COMMAND, except its standard streams get their buffering ops modified. that's it. that's the tea. ☕

mandatory arguments to long options are mandatory for short options too — yeah, the rules apply both ways, fr fr.

  • -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. short king behavior. 👑
  • --version — output version information and exit. 💫

🎀 what even is MODE 🎀

okay this is the part everyone skips and then gets confused, so like, don't skip it bestie.

  • if MODE is 'L', the corresponding stream will be line buffered. 🧚 but — and this is important — this option is invalid with standard input. not allowed. don't try it.
  • if MODE is '0', the corresponding stream will be unbuffered. zero thoughts, just output. 💀
  • otherwise, MODE is a number, and it may be followed by one of these little suffix cuties:
    • 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. so if it's not working, it might lowkey be their fault, not yours. 🙈

🫶 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. iconic pipeline behavior, honestly. this is the one you came here for. 🔥

💀 BUGS 💀

on GLIBC platforms, specifying a buffer size — i.e., using fully buffered mode — will result in undefined operation. not "maybe weird", not "probably fine". undefined. so like, be careful bestie, that's genuinely not a vibe. 😭

🌸 AUTHOR 🌸

written by Padraig Brady. king behavior. 👑

🎀 REPORTING BUGS 🎀

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. (yes the all-caps is theirs, it's giving legal drama and honestly? deserved.) 💅

🦋 SEE ALSO 🦋

so yeah, that's the whole page. this is <strong>GNU coreutils 9.12</strong>, dated <strong>September 2026</strong> — the era-defining release, if you will. go forth and unbuffer your streams, bestie. you ate. periodt. 💖✨🎀

📦 where this page comes from