fchmod (3)

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.

NAME

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);

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

chmod(), chown(), creat(), fcntl(), fstatat(), fstatvfs(), mknod(), open(), read(), write() The Base Definitions volume of POSIX.1-2008, <sys_stat.h>

COPYRIGHT

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 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 www.kernel.org/doc/man-pages/reporting_bugs.html .