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getaccess.2 (2010 09)

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getaccess(2) getaccess(2)
NAME
getaccess() - get a user’s effective access rights to a file
SYNOPSIS
#include <sys/getaccess.h>
int getaccess(
const char *path,
uid_t uid,
int ngroups,
const gid_t *gidset,
void *label,
void *privs
);
DESCRIPTION
getaccess() identifies the access rights (read, write, execute/search) a specific user ID has to an exist-
ing file. path points to a path name of a file. If the call succeeds, it returns a value of zero or greater,
representing the specified user’s effective access rights (modes) to the file. The rights are expressed as the
logical OR of bits (R_OK, W_OK
, and X_OK) whose values are defined in the header <unistd.h>.A
return of zero means that access is denied.
The uid parameter is a user ID. Special values, defined in
<sys/getaccess.h>
, represent the calling
process’s effective, real, or saved user ID:
UID_EUID Effective user ID.
UID_RUID Real user ID.
UID_SUID Saved user ID.
ngroups is the number of group IDs in gidset , not to exceed
sysconf(_SC_NGROUPS_MAX)
+1. Ifthe
ngroups parameter is positive, the gidset parameter is an array of group ID values to use in the check. If
ngroups is a recognized negative value, gidset is ignored. Special negative values of ngroups , defined in
<sys/getaccess.h>
, represent various combinations of the process’s effective, real, or saved user ID
and its supplementary groups list:
NGROUPS_EGID Use process’s effective group ID only.
NGROUPS_RGID Use process’s real group ID only.
NGROUPS_SGID Use process’s saved group ID only.
NGROUPS_SUPP Use process’s supplementary groups only.
NGROUPS_EGID_SUPP
Use process’s effective group ID plus supplementary groups.
NGROUPS_RGID_SUPP
Use process’s real group ID plus supplementary groups.
NGROUPS_SGID_SUPP
Use process’s saved group ID plus supplementary groups.
The label and privs parameters are placeholders for future extensions. For now, the values of these
parameters must be
(void *) 0.
The access check rules for access control lists are described in acl (5) and aclv (5). In addition, the
W_OK
bit is cleared for files on read-only file systems or shared-text programs being executed. Note that as in
access (2), the X_OK bit is not turned off for shared-text programs open for writing because there is no
easy way to know that a file open for writing is a shared-text program.
getaccess() checks each directory component of path by first using the caller’s effective user ID,
effective group ID, and supplementary groups list, regardless of the user ID specified. An error occurs,
distinct from "no access allowed," if the caller cannot search the path to the file. (In this case it is inap-
propriate for the caller to learn anything about the file.)
Comparison of access and getaccess
The following table compares various attributes of
access() and getaccess().
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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