CHMOD(2)

NAME
chmod, fchmod - change mode of file

SYNOPSIS
chmod(path, mode)
char *path;
int mode;

fchmod(fd, mode)
int fd, mode;

DESCRIPTION
The file whose name is given by path or referenced by the descriptor fd has its mode changed to mode. Modes are constructed by or'ing together some combination of the following:

     04000 set user ID on execution
     02000 set group ID on execution
     01000 save text image after execution
     00400 read by owner
     00200 write by owner
     00100 execute (search on directory) by owner
     00070 read, write, execute (search) by group
     00007 read, write, execute (search) by others

If an executable file is set up for sharing (this is the default) then mode 1000 prevents the system from abandoning the swap-space image of the program-text portion of the file when its last user terminates. Ability to set this bit is restricted to the super-user.

Only the owner of a file (or the super-user) may change the mode.

Writing or changing the owner of a file turns off the set-user-id and set-group-id bits. This makes the system somewhat more secure by protecting set-user-id (set-group-id) files from remaining set-user-id (set-group-id) if they are modified, at the expense of a degree of compatibility.

RETURN VALUE
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS
Chmod will fail and the file mode will be unchanged if:

[EPERM]
    The argument contains a byte with the high-order bit set.

[ENOTDIR]
    A component of the path prefix is not a directory.

[ENOENT]
    The pathname was too long.

[ENOENT]
    The named file does not exist.

[EACCES]
    Search permission is denied on a component of the path prefix.

[EPERM]
    The effective user ID does not match the owner of the file and the effective user ID is not the super-user.

[EROFS]
    The named file resides on a read-only file system.

[EFAULT]
    Path points outside the process's allocated address space.

[ELOOP]
    Too many symbolic links were encountered in translating the pathname.

[EIO]
    An I/O error occurred while reading from or writing to the file system.

Fchmod will fail if:

[EBADF]
    The descriptor is not valid.

[EINVAL]
    Fd refers to a socket, not to a file.

[EROFS]
    The file resides on a read-only file system.

[EPERM]
    The effective user ID does not match the owner of the file and the effective user ID is not the super-user.

[EIO]
    An I/O error occurred while reading from or writing to the file system.

SEE ALSO
open(2), chown(2)