fchmod man page

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.

fchmod — change mode of a file

Synopsis

#include <sys/stat.h>

int fchmod(int fildes, mode_t mode);

Description

The fchmod() function shall be equivalent to chmod() except that the file whose permissions are changed is specified by the file descriptor fildes.

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.

Return Value

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

Errors

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.

Examples

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 permissions.

#include <sys/stat.h>
#include <fcntl.h>

mode_t mode;
int    fildes;
...
fildes = open("/home/cnd/mod1", O_RDWR);
fchmod(fildes, S_IRWXU | S_IRWXG | S_IROTH | S_IWOTH);

See Also

chmod(), chown(), creat(), fcntl(), fstatat(), fstatvfs(), mknod(), open(), read(), write()

The Base Definitions volume of POSIX.1‐2008, <sys_stat.h>

Info

2013 IEEE/The Open Group POSIX Programmer's Manual