FCHMOD(3P) POSIX Programmer's Manual FCHMOD(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
fchmod -- change mode of a file
int fchmod(int fildes, mode_t mode);
The fchmod() function shall be equivalent to chmod() except that the file whose permissions are changed is specified by the file descriptor
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() is unspecified.
If fildes refers to a socket, the behavior of fchmod() is unspecified.
If fildes refers to a STREAM (which is fattach()-ed into the file system name space) the call returns successfully, doing nothing.
Upon successful completion, fchmod() shall return 0. Otherwise, it shall return -1 and set errno to indicate the error.
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 system.
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/exe-
cute permissions, but the world only has read/write permissions.
fildes = open("/home/cnd/mod1", O_RDWR);
fchmod(fildes, S_IRWXU | S_IRWXG | S_IROTH | S_IWOTH);
chmod(), chown(), creat(), fcntl(), fstatat(), fstatvfs(), mknod(), open(), read(), write()
The Base Definitions volume of POSIX.1-2008, <sys_stat.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
ogy -- 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 Stan-
dard 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 https://www.kernel.org/doc/man-pages/reporting_bugs.html .
/The Open Group 2013 FCHMOD(3P)