| GETGRENT(3) |
AerieBSD 1.0 Refernce Manual |
GETGRENT(3) |
NAME
getgrent —
getgrnam,
getgrnam_r,
getgrgid,
getgrgid_r,
setgroupent,
setgrent,
endgrent
group database operations
SYNOPSIS
#include <sys/types.h>
#include <grp.h>
structgroup *
getgrent(void);
structgroup *
getgrnam(const char *name);
int
getgrnam_r(const char *name, struct group *grp, char *buffer, size_t bufsize, struct group **result);
structgroup *
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);
DESCRIPTION
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 structure
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 programs
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 structure pointed to by
grp
and store a pointer to that structure at the location 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.
YP SUPPORT
If YP is active, the functions
getgrent();
and
getgrnam();
also use the
group.byname
YP map and the function
getgrgid();
also uses the
group.bygid
YP map in addition to the group file,
respecting the order of normal and YP entries in the group file.
RETURN VALUES
The functions
getgrent();,
getgrnam();,
and
getgrgid();
return a pointer to the group entry if successful; if end-of-file
is reached or an error occurs a null pointer is returned.
The
setgroupent();
function returns the value 1 if successful, otherwise 0.
The
endgrent();
and
setgrent();
functions 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.
FILES
- /etc/group
-
group database file
SEE ALSO
getpwent(3),
ypclnt(3),
group(5),
yp(8)
HISTORY
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 historic function
setgrfile(3),
which allowed the specification of alternate group databases, has
been deprecated and is no longer available.
BUGS
The functions
getgrent();,
getgrnam();,
getgrgid();,
setgroupent();,
and
setgrent();
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 possible.
| AerieBSD 1.0 Reference Manual |
December 26 2008 |
GETGRENT(3) |