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.
The fchmod() function shall be equivalent to chmod() except that the
file whose permissions are changed is specified by the file
If fildes references a shared memory object, the fchmod() function
need only affect the S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and
S_IWOTH file permission bits.
If fildes references a typed memory object, the behavior of fchmod()
If fildes refers to a socket, the behavior of fchmod() is
If fildes refers to a STREAM (which is fattach()-ed into the file
system name space) the call returns successfully, doing nothing.
The fchmod() function shall fail if:
EBADF The fildes argument is not an open file descriptor.
EPERM The effective user ID does not match the owner of the file and
the process does not have appropriate privileges.
EROFS The file referred to by fildes resides on a read-only file
The fchmod() function may fail if:
EINTR The fchmod() function was interrupted by a signal.
EINVAL The value of the mode argument is invalid.
EINVAL The fildes argument refers to a pipe and the implementation
disallows execution of fchmod() on a pipe.
The following sections are informative.
Changing the Current Permissions for a File
The following example shows how to change the permissions for a file
named /home/cnd/mod1 so that the owner and group have
read/write/execute permissions, but the world only has read/write
#include <sys/stat.h>#include <fcntl.h>
fildes = open("/home/cnd/mod1", O_RDWR);
fchmod(fildes, S_IRWXU | S_IRWXG | S_IROTH | S_IWOTH);
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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
IEEE/The Open Group 2013 FCHMOD(3P)