XATTR_NAME_WITH_FLAGS(3)

NAME
xattr_preserve_for_intent, xattr_name_with_flags, xattr_name_without_flags, xattr_flags_from_name, xattr_intent_with_flags

LIBRARY
libc

SYNOPSIS
#include <xattr_properties.h>
int
xattr_preserve_for_intent(const char *, xattr_operation_intent_t);
char *
xattr_name_with_flags(const char *, xattr_flags_t);
char *
xattr_name_without_flags(const char *);
xattr_flags_t
xattr_flags_from_name(const char *);
int
xattr_intent_with_flags(xattr_operation_intent_t, xattr_flags_t);

DESCRIPTION
These functions are used in conjunction with copying extended attributes from one file to another. Various types of copying (an "intent") check flags to determine which is allowed or not.

The xattr_name_with_flags() function returns an extended attribute name with the appropriate flags encoded as a string; the xattr_name_without_flags() undoes this, giving the name of the extended attribute without the flags encoding. The slight inverse of that is xattr_flags_from_name(), which will return the flags encoded in a name.

The values returned by xattr_name_with_flags() and xattr_name_without_flags() are allocated using malloc(3), and should be released by the caller, using free(3).

These functions also have an internal table of pre-defined names, maintained by the operating system.

The function xattr_intent_with_flags() will return 0 if the flags argument indicates it should not be preserved for the given intent, or 1 if it should.

The function xattr_presere_for_intent() combines the functions above, and will return zero if the named extended attribute should be preserved during a copy for the given intent.

INTENT
xattr_operation_intent_t

The type is an integral type, which is used to indicate what the intent for the operation is. The following intent values are defined:

XATTR_OPERATION_INTENT_COPY
    Indicates that the intent is to simply copy from the source to the destination. E.g., with cp. Most extended attributes should generally be preserved in this case.

XATTR_OPERATION_INTENT_SAVE
    Indicates that intent is to perform a save (perhaps as in a "safe save"). This differs from a copy in that the content may be changing; the destination may be over-writing or replacing the source, and som extended attributes should not be preserved during this process.

XATTR_OPERATION_INTENT_SHARE
    Indicates that the intent is to share, or export, the object. For example, saving as an attachment in an email message, or placing in a public folder. Sensitive information should probably not be preserved in this case.

XATTR_OPERATION_INTENT_SYNC
    Indicates that the intent is to sync the object to a service like iCloud.

FLAGS
xattr_flags_t(;)

Various flags are defined by the type the currently-defined values for this are

XATTR_FLAG_NO_EXPORT
    This indicates that the extended attribute should not be exported, or shared. This is used with XATTR_OPERATION_INTENT_SHARE.

XATTR_FLAG_CONTENT_DEPENDENT
    This indicates that the extended attribute is tied to the contents of the file (or vice versa), such that it should be re-created when the contents are changed. A checksum, for example, should not be copied, and would thus be marked with this flag.

XATTR_FLAG_NEVER_PRESERVE
    This indicates that the extended attribute should never be copied from a source object to a destination, no matter what the given intent is.

XATTR_FLAG_SYNCABLE
    This indicates that the extended attribute should be copied when the file is synced on services like iCloud. Sync services tends to want the metadata synced to be kept to a bare minimum, and may enforce additional restrictions on the acceptable size and number of extended attributes.

EXAMPLE
The following example is a simple function that, given an extended attribute name and an operation intent, will return whether or not the extended attribute should be copied. (This essentially does what xattr_preserve_for_intent() does.)

    int
    ShouldCopyEA(const char *eaName, xattr_operation_intent_t intent)
    {
    	xattr_flags_t flags = xattr_flags_from_name(eaName);
    	return xattr_intent_with_flags(intent, flags);
    }

HISTORY
These functions first appeared in Mac OS in 2013.