GETEUID(3P)

💖 GETEUID(3P) — the POSIX Programmer's Manual, bestie edition 💖

okay so real talk before we even start: this page lives in the POSIX Programmer's Manual. That means it's the standard, the blueprint, the vibe. The Linux implementation of this interface may differ (so if you're on Linux, go peek at the matching Linux manual page for the actual tea 🍵), or honestly the interface might not even be implemented on Linux at all. Just so you know what you're walking into. 🫶

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✨ PROLOG ✨

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

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🎀 NAME 🎀

geteuid — get the effective user ID

like, who are you really, underneath it all? this function knows. 👑

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🌸 SYNOPSIS 🌸

#include <unistd.h>

uid_t geteuid(void);

short. clean. iconic. no arguments, no drama. ✨

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💅 DESCRIPTION 💅

The geteuid() function shall return the effective user ID of the calling process. That's the ID that actually matters for permission checks — your real one is like, your legal name, but this is the one the system listens to. 💖

And here's the lil detail people always forget: geteuid() shall not modify errno. It leaves errno exactly as it found it. Not touching it. Respecting its space. 🧚

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🌈 RETURN VALUE 🌈

geteuid() shall always be successful, and no return value is reserved to indicate an error. There's no "oops" return. There's no secret failure code. It just gives you the ID, every time, no cap. 💯

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🍓 ERRORS 🍓

No errors are defined.

The following sections are informative.

like bestie, there is genuinely nothing here. it cannot fail. move along. 🙈

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🦋 EXAMPLES 🦋

None.

(the standard said "figure it out yourself, gorgeous" 💅)

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⭐ APPLICATION USAGE ⭐

None.

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🔥 RATIONALE 🔥

In a conforming environment, geteuid() will always succeed — that's the whole point of it. 💫

But plot twist: it is possible for implementations to provide an extension where a process in a non-conforming environment will not be associated with a user or group ID. Rude of that environment honestly. 😭

It is recommended that such implementations return (uid_t)-1 and set errno to indicate such an environment. And no, that doesn't violate this standard — because such an environment is already an extension. It's giving "we're outside the rules anyway so we make the rules". Periodt. 👑

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🧚 FUTURE DIRECTIONS 🧚

None.

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👑 SEE ALSO 👑

• getegid()
• getgid()
• getuid()
• setegid()
• seteuid()
• setgid()
• setregid()
• setreuid()
• setuid()

The Base Definitions volume of POSIX.1‐2017, <sys_types.h>, <unistd.h>

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💜 COPYRIGHT 💜

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group.

In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. 🏆

The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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and that's the whole page bestie!! this one was brought to you by IEEE/The Open Group, 2017 — aka the group chat that's been running since forever and still hasn't muted. 🫶✨💖 go get that effective user ID, you're doing amazing. 🎀🦋🌈