LIBSTDBUF(3)

💅 libstdbuf(3) — Library Functions Manual ✨

okay so picture this: a little library named libstdbuf, and its whole ~main character~ job is to change how standard input, standard output and standard error get buffered at startup. That's it. That's the gig. 👑

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🌸 NAME 🌸

libstdbuf — a preloaded library to change standard streams' initial buffering. no cap, that's literally the entire name section, she's concise 💅

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🦋 DESCRIPTION 🦋

So the libstdbuf library is meant to be preloaded using the LD_PRELOAD environment variable — preloading it is the whole way it does its thing — so that it can change the initial buffering of the standard input, standard output, and standard error streams. ✨

Now, you can load and configure this library manually if you're feeling ✨manual✨ about it, but there's also a utility — stdbuf(1) — that runs a command with the appropriate environment variables already set up for you. So like, that's the easy button. 🫶

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🎀 ENVIRONMENT 🎀

Each stream gets configured independently through its own environment variable (and the values are defined right below, don't worry bestie):

• _STDBUF_I — the initial buffering definition for the standard input stream 💖
• _STDBUF_O — the initial buffering definition for the standard output stream 💜
• _STDBUF_E — the initial buffering definition for the standard error stream 🦋

And each one of those variables can take one of these values:

• "0" — unbuffered 🏃‍♀️
• "L" — line buffered ⭐
• "B" — fully buffered, with the default buffer size 🎀
• size — fully buffered with a buffer of size bytes (and yes, the suffixes 'k', 'M' and 'G' are accepted) 🔥

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🌈 EXAMPLE 🌈

okay here's the vibe: in this example, the stdout stream of the awk(1) command will be fully buffered by default, because it does not refer to a terminal. (rude, but okay.) So libstdbuf is used to force it to be line-buffered, so that vmstat(8)'s output will not stall until the full buffer fills. icon behavior, honestly. ✨

# vmstat 1 | LD_PRELOAD=/usr/lib/libstdbuf.so \
    STDBUF_1=L awk '$2 > 1 || $3 > 1' | cat -n

Copy that block character for character, bestie — I'm not touching a single letter of it. 🙈

And if you want a simpler way to do this, see stdbuf(1). 💅

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🧚 SEE ALSO 🧚

• rtld(1)
• stdbuf(1)

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👑 HISTORY 👑

The libstdbuf library first appeared in FreeBSD 8.4. a lil retro, we stan ⭐

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💖 AUTHORS 💖

The original idea of the libstdbuf command comes from Padraig Brady, who implemented it in the GNU coreutils. Jeremie Le Hen implemented it on FreeBSD. kings, both of them 🫶👑

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so yeah, that's the whole page — this one came from Debian, dated June 29, 2023, and that's your sign-off bestie 🎀💜 go buffer responsibly ✨