acl_get_qualifier - retrieve the qualifier from an ACL entry
Linux Access Control Lists library (libacl, -lacl).
The acl_get_qualifier() function retrieves the qualifier from the ACL
entry indicated by the argument entry_d into working storage and returns
a pointer to that storage.
If the value of the tag type in the ACL entry referred to by entry_d is
ACL_USER, then the value returned by acl_get_qualifier() is a pointer to
type uid_t. If the value of the tag type in the ACL entry referred to by
entry_d is ACL_GROUP, then the value returned by acl_get_qualifier() is a
pointer to type gid_t. If the tag type in the ACL entry referred to by
entry_d is a tag type for which a qualifier is not supported,
acl_get_qualifier() returns a value of (void *)NULL and the function
fails. Subsequent operations using the returned pointer operate on an
independent copy of the qualifier in working storage, and will not change
the qualifier of the ACL entry.
This function may cause memory to be allocated. The caller should free
any releasable memory, when the new qualifier is no longer required, by
calling acl_free() with the void * value returned by acl_get_qualifier()
as an argument.
The argument entry_d and any other ACL entry descriptors that refer to
entries within the ACL containing the entry referred to by entry_d
continue to refer to those entries. The order of all existing entries in
the ACL containing the entry referred to by entry_d remains unchanged.
On success, the function returns a pointer to the tag qualifier that was
retrieved into ACL working storage. On error, a value of (void *)NULL is
returned and errno is set appropriately.
If any of the following conditions occur, the acl_get_qualifier()
function returns (void *)NULL and sets errno to the corresponding value:
[EINVAL] The argument entry_d is not a valid descriptor for an
The value of the tag type in the ACL entry referenced
by the argument entry_d is neither ACL_USER nor
[ENOMEM] The value to be returned requires more memory than is
allowed by the hardware or system-imposed memory
IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned)
acl_create_entry(3), acl_free(3), acl_get_entry(3), acl_get_permset(3),
acl_get_tag_type(3), acl_set_permset(3), acl_set_qualifier(3),
Derived from the FreeBSD manual pages written by Robert N M Watson
〈rwatson@FreeBSD.org〉, and adapted for Linux by Andreas Gruenbacher