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GETGRENT(3) Library Functions Manual GETGRENT(3)

getgrent, getgrnam, getgrnam_r, getgrgid, getgrgid_r, getgruuid, getgruuid_r, setgroupent, setgrent, endgrent — group database operations

Standard system libraries.

#include <grp.h>
#include <uuid/uuid.h>

struct group *
getgrent(void);

struct group *
getgrnam(const char *name);

int
getgrnam_r(const char *name, struct group *grp, char *buffer, size_t bufsize, struct group **result);

struct group *
getgrgid(gid_t gid);

int
getgrgid_r(gid_t gid, struct group *grp, char *buffer, size_t bufsize, struct group **result);

int
getgruuid(uuid_t uuid);

int
getgruuid_r(uuid_t uuid, struct group *grp, char *buffer, size_t bufsize, struct group **result);

int
setgroupent(int stayopen);

void
setgrent(void);

void
endgrent(void);

These functions obtain information from opendirectoryd(8), including records in /etc/group which is described in group(5). Each line of the database is defined by the structure group found in the include file <grp.h>:

struct group {
	char	*gr_name;	/* group name */
	char	*gr_passwd;	/* group password */
	gid_t	gr_gid;		/* group id */
	char	**gr_mem;	/* group members */
};

The functions (), (), and () search the group database for the given group name pointed to by name, the group id given by gid, or the UUID given by uuid respectively, returning the first one encountered. Identical group names, group gids, or uuids may result in undefined behavior.

Note that the groups file /etc/group does not contain group UUIDs. The UUID for a group may be found using ().

On OS X, these routines are thread-safe and return a pointer to a thread-specific data structure. The contents of this data structure are automatically released by subsequent calls to any of these routines on the same thread, or when the thread exits. These routines are therefore unsuitable for use in libraries or frameworks, from where they may overwrite the per-thread data that the calling application expects to find as a result of its own calls to these routines. Library and framework code should use the alternative reentrant variants detailed below.

The () function searches all available directory services on it's first invocation. It caches the returned entries in a list and returns group entries one at a time.

that () may cause a very lengthy search for group records by opendirectoryd and may result in a large number of group records being cached by the calling process. Use of this function is not advised.

The functions (), (), and () are alternative versions of getgrnam(), getgrgid(), and getgruuid() respectively. The caller must provide storage for the results of the search in the grp, buffer, bufsize, and result arguments. When these functions are successful, the grp argument will be filled-in, and a pointer to that argument will be stored in result. If an entry is not found or an error occurs, result will be set to NULL.

These functions will open the group file for reading, if necessary.

The () function causes getgrent() to ``rewind'' to the beginning of the list of entries cached by a previous getgrent() call. The cache is not cleared. The stayopen parameter value is unused on OS X.

The () and () functions clear the cached results from a previous getgrent() call.

The functions getgrent(), getgrnam(), and getgrgid(), return a pointer to a group structure on success or NULL if the entry is not found or if an error occurs. If an error does occur, errno will be set. Note that programs must explicitly set errno to zero before calling any of these functions if they need to distinguish between a non-existent entry and an error. The functions getgrnam_r(), getgrgid_r(), and getgruuid_r() return 0 if no error occurred, or an error number to indicate failure. It is not an error if a matching entry is not found. (Thus, if result is set to NULL and the return value is 0, no matching entry exists.)

setgroupent() returns the value 1 if successful, otherwise the value 0 is returned. The functions setgrent(), endgrent(), and setgrfile() have no return value.

/etc/group
group database file

The historic function setgrfile(), which allowed the specification of alternate group databases, has been deprecated and is no longer available.

getpwent(3), group(5), mbr_gid_to_uuid(3,) opendirectory(8), yp(8)

The getgrent(), getgrnam(), getgrnam_r(), getgrgid(), getgrgid_r() and endgrent() functions conform to ISO/IEC 9945-1:1996 (“POSIX.1”). The setgrent() function differs from that standard in that its return type is int rather than void.

The functions endgrent(), getgrent(), getgrnam(), getgrgid(), and setgrent() appeared in Version 7 AT&T UNIX. The functions setgrfile() and setgroupent() appeared in 4.3BSD-Reno. The functions getgrnam_r() and getgrgid_r() appeared in FreeBSD 5.1. The functions getgruuid() and getgruuid_r() appeared in Mac OS X 10.8.

The functions getgrent(), getgrnam(), getgrgid(), getgruuid(), setgroupent() and setgrent() leave their results in an internal thread-specific memory and return a pointer to that object. Subsequent calls to the same function will modify the same object.

October 26, 2011 macOS