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.

^[SHM] 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.

^[TYM] 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.

^[XSR] 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 privilege.

[EROFS]

The file referred to by fildes resides on a read-only file system.

The fchmod() function may fail if:

[EINTR]

^[XSI] The fchmod() function was interrupted by a signal.

[EINVAL]

^[XSI] 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.

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() , fstatvfs() , mknod() , open() , read() , stat() , write() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE and aligned with fchmod() in the POSIX Realtime Extension. Specifically, the second paragraph of the DESCRIPTION is added and a second instance of [EINVAL] is defined in the list of optional errors.

Issue 6

The DESCRIPTION is updated for alignment with IEEE Std 1003.1j-2000 by stating that fchmod() behavior is unspecified for typed memory objects.