GETGRENT(3) BSD Programmer's Manual GETGRENT(3)
getgrent, getgrnam, getgrnam_r, getgrgid, getgrgid_r, setgroupent,
setgrent, endgrent - group database operations
#include <sys/types.h>
#include <grp.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
setgroupent(int stayopen);
void
setgrent(void);
void
endgrent(void);
These functions operate on the group database file /etc/group which is
described in group(5). Each line of the database is defined by the struc-
ture struct 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 getgrnam() and getgrgid() search the group database for the
given group name pointed to by name or the group ID pointed to by gid,
respectively, returning the first one encountered. Identical group names
or group GIDs may result in undefined behavior.
getgrent() sequentially reads the group database and is intended for pro-
grams that wish to step through the complete list of groups.
All three routines will open the group file for reading, if necessary.
setgroupent() opens the file, or rewinds it if it is already open. If
stayopen is non-zero, file descriptors are left open, significantly
speeding subsequent function calls. This functionality is unnecessary for
getgrent() as it doesn't close its file descriptors by default. It should
also be noted that it is dangerous for long-running programs to use this
functionality as the group file may be updated.
setgrent() is equivalent to setgroupent() with an argument of zero.
The endgrent() function closes any open files.
The getgrgid_r() and getgrnam_r() functions both update the group struc-
ture pointed to by grp and store a pointer to that structure at the loca-
tion pointed to by result. The structure is filled with an entry from the
group database with a matching gid or name. Storage referenced by the
group structure will be allocated from the memory provided with the
buffer parameter, which is bufsiz characters in size.
The functions getgrent(), getgrnam(), and getgrgid() return a pointer to
the group entry if successful; if end-of-file is reached or an error oc-
curs a null pointer is returned. The setgroupent() function returns the
value 1 if successful, otherwise 0. The endgrent() and setgrent() func-
tions have no return value. The functions getgrgid_r() and getgrnam_r()
store a null pointer at the location pointed to by result and return the
error number if an error occurs, or the requested entry is not found.
/etc/group group database file
getpwent(3), group(5)
The functions endgrent(), getgrent(), getgrnam(), getgrgid(), and set-
grent() appeared in Version 7 AT&T UNIX. The functions setgrfile() and
setgroupent() appeared in 4.3BSD-Reno.
The historic function setgrfile(3), which allowed the specification of
alternate group databases, has been deprecated and is no longer avail-
able.
The functions getgrent(), getgrnam(), getgrgid(), setgroupent(), and set-
grent() leave their results in an internal static object and return a
pointer to that object. Subsequent calls to the same function will modify
the same object.
The functions getgrent(), endgrent(), setgroupent(), and setgrent() are
fairly useless in a networked environment and should be avoided, if pos-
sible.
MirBSD #10-current April 19, 1994 1