chflags

CHFLAGS(2)                    System Calls Manual                   CHFLAGS(2)

NAME
     chflags, lchflags, fchflags, chflagsat — set file flags

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/stat.h>
     #include <unistd.h>

     int
     chflags(const char *path, unsigned long flags);

     int
     lchflags(const char *path, unsigned long flags);

     int
     fchflags(int fd, unsigned long flags);

     int
     chflagsat(int fd, const char *path, unsigned long flags, int atflag);

DESCRIPTION
     The file whose name is given by path or referenced by the descriptor fd
     has its flags changed to flags.

     The lchflags() system call is like chflags() except in the case where the
     named file is a symbolic link, in which case lchflags() will change the
     flags of the link itself, rather than the file it points to.

     The chflagsat() is equivalent to either chflags() or lchflags() depending
     on the atflag except in the case where path specifies a relative path.
     In this case the file to be changed is determined relative to the
     directory associated with the file descriptor fd instead of the current
     working directory.  The values for the atflag are constructed by a
     bitwise-inclusive OR of flags from the following list, defined in
     <fcntl.h>:

     AT_SYMLINK_NOFOLLOW
             If path names a symbolic link, then the flags of the symbolic
             link are changed.

     If chflagsat() is passed the special value AT_FDCWD in the fd parameter,
     the current working directory is used.  If also atflag is zero, the
     behavior is identical to a call to chflags().

     The flags specified are formed by or'ing the following values

           SF_APPEND     The file may only be appended to.
           SF_ARCHIVED   The file has been archived.  This flag means the
                         opposite of the DOS, Windows and CIFS
                         FILE_ATTRIBUTE_ARCHIVE attribute.  This flag has been
                         deprecated, and may be removed in a future release.
           SF_IMMUTABLE  The file may not be changed.
           SF_NOUNLINK   The file may not be renamed or deleted.
           SF_SNAPSHOT   The file is a snapshot file.
           UF_APPEND     The file may only be appended to.
           UF_ARCHIVE    The file needs to be archived.  This flag has the
                         same meaning as the DOS, Windows and CIFS
                         FILE_ATTRIBUTE_ARCHIVE attribute.  Filesystems in
                         FreeBSD may or may not have special handling for this
                         flag.  For instance, ZFS tracks changes to files and
                         will set this bit when a file is updated.  UFS only
                         stores the flag, and relies on the application to
                         change it when needed.
           UF_HIDDEN     The file may be hidden from directory listings at the
                         application's discretion.  The file has the DOS,
                         Windows and CIFS FILE_ATTRIBUTE_HIDDEN attribute.
           UF_IMMUTABLE  The file may not be changed.
           UF_NODUMP     Do not dump the file.
           UF_NOUNLINK   The file may not be renamed or deleted.
           UF_OFFLINE    The file is offline, or has the Windows and CIFS
                         FILE_ATTRIBUTE_OFFLINE attribute.  Filesystems in
                         FreeBSD store and display this flag, but do not
                         provide any special handling when it is set.
           UF_OPAQUE     The directory is opaque when viewed through a union
                         stack.
           UF_READONLY   The file is read only, and may not be written or
                         appended.  Filesystems may use this flag to maintain
                         compatibility with the DOS, Windows and CIFS
                         FILE_ATTRIBUTE_READONLY attribute.
           UF_REPARSE    The file contains a Windows reparse point and has the
                         Windows and CIFS FILE_ATTRIBUTE_REPARSE_POINT
                         attribute.
           UF_SPARSE     The file has the Windows FILE_ATTRIBUTE_SPARSE_FILE
                         attribute.  This may also be used by a filesystem to
                         indicate a sparse file.
           UF_SYSTEM     The file has the DOS, Windows and CIFS
                         FILE_ATTRIBUTE_SYSTEM attribute.  Filesystems in
                         FreeBSD may store and display this flag, but do not
                         provide any special handling when it is set.

     If one of SF_IMMUTABLE, SF_APPEND, or SF_NOUNLINK is set a non-super-user
     cannot change any flags and even the super-user can change flags only if
     securelevel is 0.  (See init(8) for details.)

     The UF_IMMUTABLE, UF_APPEND, UF_NOUNLINK, UF_NODUMP, and UF_OPAQUE flags
     may be set or unset by either the owner of a file or the super-user.

     The SF_IMMUTABLE, SF_APPEND, SF_NOUNLINK, and SF_ARCHIVED flags may only
     be set or unset by the super-user.  Attempts to toggle these flags by
     non-super-users are rejected.  These flags may be set at any time, but
     normally may only be unset when the system is in single-user mode.  (See
     init(8) for details.)

     The implementation of all flags is filesystem-dependent.  See the
     description of the UF_ARCHIVE flag above for one example of the
     differences in behavior.  Care should be exercised when writing
     applications to account for support or lack of support of these flags in
     various filesystems.

     The SF_SNAPSHOT flag is maintained by the system and cannot be toggled.

RETURN VALUES
     Upon successful completion, the value 0 is returned; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The chflags() system call will fail if:

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

     [ENAMETOOLONG]     A component of a pathname exceeded 255 characters, or
                        an entire path name exceeded 1023 characters.

     [ENOENT]           The named file does not exist.

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

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

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

     [EPERM]            One of SF_IMMUTABLE, SF_APPEND, or SF_NOUNLINK is set
                        and the user is either not the super-user or
                        securelevel is greater than 0.

     [EPERM]            A non-super-user attempted to toggle one of
                        SF_ARCHIVED, SF_IMMUTABLE, SF_APPEND, or SF_NOUNLINK.

     [EPERM]            An attempt was made to toggle the SF_SNAPSHOT flag.

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

     [EFAULT]           The path argument points outside the process's
                        allocated address space.

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

     [EOPNOTSUPP]       The underlying file system does not support file
                        flags, or does not support all of the flags set in
                        flags.

     The fchflags() system call will fail if:

     [EBADF]            The descriptor is not valid.

     [EINVAL]           The fd argument refers to a socket, not to a file.

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

     [EPERM]            One of SF_IMMUTABLE, SF_APPEND, or SF_NOUNLINK is set
                        and the user is either not the super-user or
                        securelevel is greater than 0.

     [EPERM]            A non-super-user attempted to toggle one of
                        SF_ARCHIVED, SF_IMMUTABLE, SF_APPEND, or SF_NOUNLINK.

     [EPERM]            An attempt was made to toggle the SF_SNAPSHOT flag.

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

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

     [EOPNOTSUPP]       The underlying file system does not support file
                        flags, or does not support all of the flags set in
                        flags.

SEE ALSO
     chflags(1), fflagstostr(3), strtofflags(3), init(8), mount_unionfs(8)

HISTORY
     The chflags() and fchflags() system calls first appeared in 4.4BSD.  The
     lchflags() system call first appeared in FreeBSD 5.0.  The chflagsat()
     system call first appeared in FreeBSD 10.0.

                                March 22, 2013