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HP-UX 11i Version 3: February 2007

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chownacl() — change owner and/or group represented in a file's access control list (ACL) (HFS File Systems only)


#include <acllib.h>

void chownacl( int nentries, const struct acl_entry *acl, uid_t olduid, gid_t oldgid, uid_t newuid, gid_t newgid );


To ensure continued conformance with emerging industry standards, features described in this manual entry are likely to change in a future release.


This routine alters an access control list (ACL) to reflect the change in a file's owner or group ID when an old file is copied to a new file and the ACL is also copied. chownacl() transfers ownership (that is, it modifies base ACL entries) in a manner similar to chown() (see chown(2)). The algorithm is described below and also in acl(5).

The nentries parameter is the current number of ACL entries in the acl[] array (zero or more; a negative value is treated as zero). The olduid and oldgid values are the user and group IDs of the original file's owner, typically the st_uid and st_gid values from stat() (see stat(2)). The newuid and newgid values are the user and group IDs of the new file's owner, typically the return values from geteuid() and getegid() (see geteuid(2) and getegid(2) in getuid(2)).

If an ACL entry in acl[] has a uid of olduid and a gid of ACL_NSGROUP (that is, an owner base ACL entry), chownacl() changes uid to newuid (with exceptions - see below). If an entry has a uid of ACL_NSUSER and a gid of oldgid (that is, a group base ACL entry), chownacl() changes gid to newgid. In either case, only the last matching ACL entry is altered; a valid ACL can have only one of each type.

As with chown(2), if the new user or group already has an ACL entry (that is, a uid of newuid and a gid of ACL_NSGROUP, or a uid of ACL_NSUSER and a gid of newgid), chownacl() does not change the old user or group base ACL entry; both the old and new ACL entries are preserved.

As a special case, if olduid (oldgid) is equal to newuid (newgid), chownacl() does not search acl[] for an old user (group) base ACL entry to change. Calling it with both olduid equal to newuid and oldgid equal to newgid causes chownacl() to do nothing.

Suggested Use

This routine is useful in a program that creates a new or replacement copy of a file whose original was (or possibly was) owned by a different user or group, and that copies the old file's ACL to the new file. Copying another user's and/or group's file is equivalent to having the original file's owner and/or group copy and then transfer a file to a new owner and/or group using chown(). This routine is not needed for merely changing a file's ownership; chown() modifies the ACL appropriately in that case.

If a program also copies file miscellaneous mode bits from an old file to a new one, it must use chmod() (see chmod(2)). However, since chmod() deletes optional ACL entries, it must be called before setacl() (see setacl(2)). Furthermore, to avoid leaving a new file temporarily unprotected, the chmod() call should set only the file miscellaneous mode bits, with all access permission mode bits set to zero (that is, mask the mode with 07000). The cpacl() library call encapsulates this operation, and handles remote files appropriately too.


The following code fragment gets stat() information and the ACL from oldfile, transfers ownership of newfile to the caller, and sets the revised ACL to newfile.

#include <sys/types.h> #include <sys/stat.h> #include <sys/acl.h> int nentries; struct acl_entry acl [NACLENTRIES]; struct stat statbuf; if (stat ("oldfile", & statbuf) < 0) error (...); if ((nentries = getacl ("oldfile", NACLENTRIES, acl)) < 0) error (...); chownacl (nentries, acl, statbuf.st_uid, statbuf.st_gid, geteuid(), getegid()); if (setacl ("newfile", nentries, acl)) error (...);


chownacl() is only supported on HFS file system on standard HP-UX operating system.


chownacl() was developed by HP.

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