FCHOWN(3POSIX)

👑 FCHOWN(3POSIX) 👑

okay bestie, welcome to the POSIX Programmer's Manual 💖 this is fchown(3POSIX) and she's here to change who owns your file. let's get into it ✨

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🌸 PROLOG 🌸

so like, real talk first: this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (pls go consult the corresponding Linux manual page for the details of Linux behavior, iykyk), or honestly the interface may not even be implemented on Linux at all. just a heads up, no cap 🫶

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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 🦋

okay so fchown() shall be equivalent to chown() except for one lil glow-up: the file whose owner and group are being changed is specified by the file descriptor fildes instead of a path. that's the whole vibe. main character energy, honestly 👑

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⭐ RETURN VALUE ⭐

upon successful completion, fchown() shall return 0 💖 otherwise it shall return -1 and set errno to indicate the error. not me getting a -1... 😭

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🎀 ERRORS 🎀

the fchown() function shall fail if:

• EBADF — the fildes argument is not an open file descriptor. bestie that's not even a real open fd 💀
• 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. she's locked down 🔒

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. the hardware said nope 🙈
• EINTR — the fchown() function was interrupted by a signal which was caught.

the following sections are informative. yes, like, they're just here for the lore, they're not normative 💜

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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.

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💜 RATIONALE 💜

None.

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🌸 FUTURE DIRECTIONS 🌸

None.

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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!! 🫶✨ brought to you by IEEE/The Open Group, 2017 — stay iconic, go change some ownership, and remember: the vibe changes, the facts never do 💅💖