CHFLAGS(2) FreeBSD 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.
AT_RESOLVE_BENEATH
Only walk paths below the directory specified by the fd
descriptor. See the description of the O_RESOLVE_BENEATH flag in
the open(2) manual page.
AT_EMPTY_PATH
If the path argument is an empty string, operate on the file or
directory referenced by the descriptor fd. If fd is equal to
AT_FDCWD, operate on the current working directory.
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SF_ARCHIVED The file has been archived.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.
[EINTEGRITY] Corrupted data was detected while reading from 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.
[EINTEGRITY] Corrupted data was detected while reading from the
file system.
[EOPNOTSUPP] The underlying file system does not support file
flags, or does not support all of the flags set in
flags.
[ENOTCAPABLE] path is an absolute path, or contained a ".."
component leading to a directory outside of the
directory hierarchy specified by fd, and the process
is in capability mode or the AT_RESOLVE_BENEATH flag
was specified.
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.
FreeBSD 13.1-RELEASE-p6 March 30, 2021 FreeBSD 13.1-RELEASE-p6
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