'\" et
.TH FCHOWN "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH 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.
.\"
.SH NAME
fchown
\(em change owner and group of a file
.SH SYNOPSIS
.LP
.nf
#include <unistd.h>
.P
int fchown(int \fIfildes\fP, uid_t \fIowner\fP, gid_t \fIgroup\fP);
.fi
.SH DESCRIPTION
The
\fIfchown\fR()
function shall be equivalent to
\fIchown\fR()
except that the file whose owner and group are changed is
specified by the file descriptor
.IR fildes .
.SH "RETURN VALUE"
Upon successful completion,
\fIfchown\fR()
shall return 0. Otherwise, it shall return \-1 and set
.IR errno
to indicate the error.
.SH ERRORS
The
\fIfchown\fR()
function shall fail if:
.TP
.BR EBADF
The
.IR fildes
argument is not an open file descriptor.
.TP
.BR 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.
.TP
.BR EROFS
The file referred to by
.IR fildes
resides on a read-only file system.
.P
The
\fIfchown\fR()
function may fail if:
.TP
.BR EINVAL
The owner or group ID is not a value supported by the implementation.
The
.IR fildes
argument refers to a pipe or socket
or an
\fIfattach\fR()-ed
STREAM
and the implementation disallows execution of
\fIfchown\fR()
on a pipe.
.TP
.BR EIO
A physical I/O error has occurred.
.TP
.BR EINTR
The
\fIfchown\fR()
function was interrupted by a signal which was caught.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
.SS "Changing the Current Owner of a File"
.P
The following example shows how to change the owner of a file named
.BR /home/cnd/mod1
to ``jones'' and the group to ``cnd''.
.P
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.
.sp
.RS 4
.nf

#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <pwd.h>
#include <grp.h>
.P
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);
.fi
.P
.RE
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIchown\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<unistd.h>\fP"
.\"
.SH 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 .
.PP
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 .