FCHOWN(3P)

💅 FCHOWN(3P) — like, the POSIX Programmer's Manual one, bestie

okay so before we even get into it, real talk: this page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so go check the corresponding Linux manual page for the actual Linux tea), or the interface might not even be implemented on Linux at all. 🙈 Not me warning you first thing.

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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 🎀

fchown — change owner and group of a file

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🌸 SYNOPSIS 🌸

#include <unistd.h>

int fchown(int fildes, uid_t owner, gid_t group);

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🦋 DESCRIPTION 🦋

So the fchown() function shall be equivalent to chown() except for one lil glow-up: the file whose owner and group are getting changed is specified by the file descriptor fildes instead. That's it, that's the whole vibe. 💖

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👑 RETURN VALUE 👑

Upon successful completion, fchown() shall return 0. Iconic. Otherwise it shall return -1 and set errno to indicate the error. 😭

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🔥 ERRORS 🔥

The fchown() function shall fail if:

• EBADF — The fildes argument is not an open file descriptor. Bestie. It's not even open.
• EPERM — The effective user ID does not match the owner of the file, or the process does not have appropriate privileges, and _POSIX_CHOWN_RESTRICTED indicates that such privilege is required.
• EROFS — The file referred to by fildes resides on a read-only file system. Read-only means read-only, no cap. 🚫

The fchown() function may fail if:

• EINVAL — The owner or group ID is not a value supported by the implementation. Also: the fildes argument refers to a pipe or socket or an fattach()-ed STREAM and the implementation disallows execution of fchown() on a pipe.
• EIO — A physical I/O error has occurred. 😬
• EINTR — The fchown() function was interrupted by a signal which was caught.

The following sections are informative. (i.e. the vibes-only section, not the legally-binding section, iykyk)

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🍓 EXAMPLES 🍓

💜 Changing the Current Owner of a File 💜

The following example shows how to change the owner of a file named /home/cnd/mod1 to jones and the group to cnd.

The numeric value for the user ID is obtained by extracting the user ID from the user database entry associated with jones. Similarly, the numeric value for the group ID is obtained by extracting the group ID from the group database entry associated with cnd. This example assumes the calling program has appropriate privileges. 👑

#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <pwd.h>
#include <grp.h>

struct passwd *pwd;
struct group  *grp;
int            fildes;
...
fildes = open("/home/cnd/mod1", O_RDWR);
pwd = getpwnam("jones");
grp = getgrnam("cnd");
fchown(fildes, pwd->pw_uid, grp->gr_gid);

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🧚 APPLICATION USAGE 🧚

None. — literally nothing here, bestie, it's a blank page and honestly? slay. 💀

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🌈 RATIONALE 🌈

None. — nope, nothing, empty. ✨

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⭐ FUTURE DIRECTIONS ⭐

None. — the future is, apparently, also blank. 🦋

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💖 SEE ALSO 💖

• chown()
• The Base Definitions volume of POSIX.1‐2017, <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 came from the POSIX Programmer's Manual, courtesy of IEEE/The Open Group, dated 2017 — so like, take it up with them if something's off, not me 🫶✨