.\"	$OpenBSD: chflags.2,v 1.29 2022/08/04 06:20:24 jsg Exp $
.\"	$NetBSD: chflags.2,v 1.6 1995/02/27 12:32:03 cgd Exp $
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.\"	@(#)chflags.2	8.1 (Berkeley) 6/9/93
.\"
.Dd $Mdocdate: August 4 2022 $
.Dt CHFLAGS 2
.Os
.Sh NAME
.Nm chflags ,
.Nm chflagsat ,
.Nm fchflags
.Nd set file flags
.Sh SYNOPSIS
.In sys/stat.h
.Ft int
.Fn chflags "const char *path"  "unsigned int flags"
.Ft int
.Fn fchflags "int fd" "unsigned int flags"
.In sys/stat.h
.In fcntl.h
.Ft int
.Fn chflagsat "int fd" "const char *path"  "unsigned int flags" "int atflags"
.Sh DESCRIPTION
The file whose name is given by
.Fa path
or referenced by the descriptor
.Fa fd
has its flags changed to
.Fa flags .
.Pp
The flags are the bitwise OR of zero or more of the following values:
.Pp
.Bl -tag -width "SF_IMMUTABLE" -compact -offset indent
.It Dv UF_NODUMP
Do not dump the file.
.It Dv UF_IMMUTABLE
The file may not be changed.
.It Dv UF_APPEND
The file may only be appended to.
.It Dv SF_ARCHIVED
The file may be archived.
.It Dv SF_IMMUTABLE
The file may not be changed.
.It Dv SF_APPEND
The file may only be appended to.
.El
.Pp
The
.Dv UF_IMMUTABLE
and
.Dv UF_APPEND
flags may be set or unset by either the owner of a file or the superuser.
.Pp
The
.Dv SF_ARCHIVED ,
.Dv SF_IMMUTABLE
and
.Dv SF_APPEND
flags may only be set or unset by the superuser.
They may be set at any time, but normally may only be unset when
the system is in single-user mode.
(See
.Xr init 8
for details.)
.Pp
The
.Fn chflagsat
function is equivalent to
.Fn chflags
except in the case where
.Fa path
specifies a relative path.
In this case the file to be changed is determined relative to the directory
associated with the file descriptor
.Fa fd
instead of the current working directory.
.Pp
If
.Fn chflagsat
is passed the special value
.Dv AT_FDCWD
(defined in
.In fcntl.h )
in the
.Fa fd
parameter, the current working directory is used.
If
.Fa atflags
is also zero, the behavior is identical to a call to
.Fn chflags .
.Pp
The
.Fa atflags
argument is the bitwise OR of zero or more of the following values:
.Pp
.Bl -tag -width AT_SYMLINK_NOFOLLOW -offset indent -compact
.It Dv AT_SYMLINK_NOFOLLOW
If
.Fa path
names a symbolic link, then the flags of the symbolic link are changed.
.El
.Pp
The
.Fn fchflags
function is equivalent to
.Fn chflags
except that the file whose flags are changed is specified
by the file descriptor
.Fa fd .
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Fn chflags
will fail if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded
.Dv NAME_MAX
characters, or an entire pathname (including the terminating NUL)
exceeded
.Dv PATH_MAX
bytes.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EPERM
The effective user ID does not match the owner of the file and
the effective user ID is not the superuser, or the effective user ID
is not the superuser and at least one of the super-user-only flags
for the named file would be changed.
.It Bq Er EOPNOTSUPP
The named file resides on a file system that does not support file
flags.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EFAULT
.Fa path
points outside the process's allocated address space.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.It Bq Er EINVAL
The
.Fa flags
value is invalid.
.It Bq Er EINVAL
The descriptor references a block or character device and the effective
user ID is not the superuser.
.El
.Pp
.Fn fchflags
will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The descriptor is not valid.
.It Bq Er EINVAL
.Fa fd
refers to a socket, not to a file.
.It Bq Er EINVAL
The descriptor references a block or character device and the effective
user ID is not the superuser.
.It Bq Er EINVAL
The
.Fa flags
value is invalid.
.It Bq Er EPERM
The effective user ID does not match the owner of the file and
the effective user ID is not the superuser, or the effective user ID
is not the superuser and at least one of the super-user-only flags
for the named file would be changed.
.It Bq Er EOPNOTSUPP
The named file resides on a file system that does not support file
flags.
.It Bq Er EROFS
The file resides on a read-only file system.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr chflags 1 ,
.Xr init 8
.Sh HISTORY
The
.Fn chflags
and
.Fn fchflags
functions first appeared in
.Bx 4.3 Reno .
The
.Fn chflagsat
function first appeared in
.Fx 10.0 .
It was added to
.Ox
in
.Ox 5.7 .