open_how(2type)

✨ open_how — how to open a pathname ✨

okay bestie, so this is open_how(2type) — it's a type, not a function, so don't go looking for a man page full of arguments, because there aren't any. it's a struct. a lil vibe container. and it tells the kernel how you want a pathname opened 💅

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📚 LIBRARY

Linux kernel headers. that's the whole vibe — it's a header thing, not a userland libc thing. 🫶

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🎀 SYNOPSIS

#include <linux/openat2.h>

struct open_how {
    u64  flags;    /* O_* flags */
    u64  mode;     /* Mode for O_{CREAT,TMPFILE} */
    u64  resolve;  /* RESOLVE_* flags */
    /* ... */
};

look at her. three little u64 fields and a mysterious /* ... */ that's highkey doing so much work. iykyk ✨

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💖 DESCRIPTION

so this struct specifies how a pathname should be opened. that's it. that's the job. she's the instruction sheet the kernel reads before opening anything for you. 🦋

the fields are as follows, bestie, and yes we're going through all of them:

• flags — this field specifies the file creation and file status flags to use when opening the file. all your O_* besties go here. 🌸
• mode — this field specifies the mode for the new file. it's the permission vibes for when you're making something new. 🎀
• resolve — this is a bit mask of flags that modify the way in which all components of a pathname will be resolved (see path_resolution(7) for background information). like, the whole path. every single component. no cap. 🧚

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👑 STANDARDS

Linux. that's it. that's the standard. we're a Linux girlie and we're not pretending otherwise. 💜

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🌈 HISTORY

okay so here's the lore, and it's actually kind of important so pay attention 🙈

extra fields may be appended to the structure, and a zero value in a new field results in the kernel behaving as though that extension field was not present.

which means — and this is the part you cannot skip, bestie — a user must zero-fill this structure on initialization.

⚠️ like fr fr. zero it out. if you leave garbage in there and the kernel reads it as some future extension field, that's a bad time and we don't do bad times. memset is your friend. slay responsibly. 💀

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🔥 SEE ALSO

• openat2(2) — the actual syscall that eats this struct. go read her next. she's the main character, this page is just her outfit. 👑

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that's the whole page, bestie!! 💖 this was Linux man-pages 6.20, dated 2025-09-21 — so like, recent, iconic, and maintained. go zero-fill your structs and stay hydrated 🫶✨🎀