CHFLAGS(2) System Calls Manual CHFLAGS(2)

chflags, fchflags, fchflagsat — set file flags

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

int
chflags(const char *path, u_int flags);

int
fchflags(int fd, u_int flags);

int
fchflagsat(int fd, const char *path, u_int flags, int flag);

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

The () is equivalent to () 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 flag are constructed by a bitwise-inclusive OR of flags from the following list, defined in <fcntl.h>:

If path names a symbolic link, then the flags of the symbolic link is changed.
If path names a symbolic link, then the flags of the symbolic link is changed and if the path has any other symbolic links, an error is returned.
If path does not reside in the hierarchy beneath the starting directory, an error is returned.

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

The flags specified are formed by 'ing the following values

UF_NODUMP
Do not dump the file.
UF_IMMUTABLE
The file may not be changed.
UF_APPEND
The file may only be appended to.
UF_OPAQUE
The directory is opaque when viewed through a union stack.
UF_HIDDEN
The file or directory is not intended to be displayed to the user.
UF_COMPRESSED
File is compressed at the file system level.
SF_ARCHIVED
The file has been archived.
SF_IMMUTABLE
The file may not be changed.
SF_APPEND
The file may only be appended to.
SF_DATALESS
The file is a dataless placeholder. The system will attempt to materialize it when accessed according to the dataless file materialization policy of the accessing thread or process. See getiopolicy_np(3).

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

The “SF_ARCHIVED”, “SF_IMMUTABLE” and “SF_APPEND” flags may only be set or unset by the super-user.

The “SF_DATALESS” and “UF_COMPRESSED” flags are internal flags and may not be set or unset from user space. Attempting to modify them using () will result in undefined behaviour.

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

chflags() will fail if:

[]
A component of the path prefix is not a directory.
[]
A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
[]
The named file does not exist.
[]
Search permission is denied for a component of the path prefix.
[]
Too many symbolic links were encountered in translating the pathname.
[]
The effective user ID does not match the owner of the file and the effective user ID is not the super-user.
[]
The named file resides on a read-only file system.
[]
Path points outside the process's allocated address space.
[]
An I/O error occurred while reading from or writing to the file system.
[]
The operation isn't supported by the filesystem.

fchflags() will fail if:

[]
The descriptor is not valid.
[]
fd refers to a socket, not to a file.
[]
The effective user ID does not match the owner of the file and the effective user ID is not the super-user.
[]
The file resides on a read-only file system.
[]
An I/O error occurred while reading from or writing to the file system.
[]
The operation isn't supported by the filesystem.

In addition to the chflags() errors, fchflagsat() fails if:

[]
The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
[]
The value of the flag argument is not valid.
[]
If AT_SYMLINK_NOFOLLOW_ANY was passed and a symbolic link was encountered in translating the pathname.
[]
The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.
[]
if AT_RESOLVE_BENEATH was passed and path does not reside in the directory hierarchy beneath the starting directory.

chflags(1), fflagstostr(3), lchflags(3), strtofflags(3), launchd(8)

The chflags() and fchflags functions first appeared in 4.4BSD. fchflagsat() system call appeared in macOS 27.0.

June 9, 1993 macOS 26