NAME
getgrent
,
getgrent_r
, getgrgid
,
getgrgid_r
, getgrnam
,
getgrnam_r
, setgroupent
,
setgrent
, endgrent
—
group database operations
LIBRARY
library “libc”
SYNOPSIS
#include
<grp.h>
struct group *
getgrent
(void);
int
getgrent_r
(struct group *grp,
char *buffer, size_t buflen,
struct group **result);
struct group *
getgrgid
(gid_t
gid);
int
getgrgid_r
(gid_t gid,
struct group *grp, char *buffer,
size_t buflen, struct group
**result);
struct group *
getgrnam
(const
char *name);
int
getgrnam_r
(const char *name,
struct group *grp, char *buffer,
size_t buflen, struct group
**result);
int
setgroupent
(int
stayopen);
void
setgrent
(void);
void
endgrent
(void);
DESCRIPTION
These functions operate on the group database 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
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 ids may result in undefined
behavior.
The
getgrent
()
function sequentially reads the group database and is intended for programs
that wish to step through the complete list of groups.
All three functions will open the group file for reading, if necessary.
The functions
getgrnam_r
(),
getgrgid_r
(),
and
getgrent_r
()
act like their non re-entrant counterparts respectively, updating the
contents of grp and storing a pointer to that in
result, and returning 0
.
Storage used by grp is allocated from
buffer, which is buflen bytes in
size. If the requested entry cannot be found, result
will point to NULL
and 0
will be returned. If an error occurs, a non-zero error number will be
returned and result will point to
NULL
. Calling getgrent_r
()
from multiple threads will result in each thread reading a disjoint portion
of the group database.
The
setgroupent
()
function opens the file, or rewinds it if it is already open. If
stayopen is non-zero, file descriptors are left open,
significantly speeding functions subsequent 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.
The
setgrent
()
function is equivalent to setgroupent
() with an
argument of zero.
The
endgrent
()
function closes any open files.
RETURN VALUES
The functions getgrgid
(),
getgrnam
(), and getgrent
()
return a valid pointer to a group structure on success and a
NULL
pointer if the entry was not found or an error
occurred. If an error occurred, the global variable
errno
is set to indicate the nature of the
failure.
The functions getgrgid_r
(),
getgrnam_r
(), and
getgrent_r
() return 0
on
success or entry not found, and non-zero on failure, setting the global
variable errno
to indicate the nature of the
failure.
The setgroupent
() function returns the
value 1 if successful, otherwise the value 0 is returned, setting the global
variable errno
to indicate the nature of the
failure.
The endgrent
() and
setgrent
() functions have no return value.
FILES
- /etc/group
- group database file
COMPATIBILITY
The historic function setgrfile
(), which
allowed the specification of alternative group databases, has been
deprecated and is no longer available.
ERRORS
The following error codes may be set in
errno for getgrent
,
getgrent_r
, getgrnam
,
getgrnam_r
, getgrgid
,
getgrgid_r
, and
setgroupent
:
- [
EINTR
] - A signal was caught during the database search.
- [
EIO
] - An I/O error has occurred.
- [
EMFILE
] - The limit on open files for this process has been reached.
- [
ENFILE
] - The system limit on open files has been reached.
The following error code may be set in errno
for getgrent_r
, getgrnam_r
,
and getgrgid_r
:
- [
ERANGE
] - The resulting struct group does not fit in the space
defined by
buffer
andbuflen
Other errno
values may be set depending on
the specific database backends.
SEE ALSO
STANDARDS
The getgrgid
() and
getgrnam
() functions conform to
IEEE Std 1003.1-1990 (“POSIX.1”). The
getgrgid_r
() and
getgrnam_r
() functions conform to
IEEE Std 1003.1c-1995 (“POSIX.1c”).
The endgrent
(), getgrent
(),
and setgrent
() functions conform to
X/Open Portability Guide Issue 4, Version 2
(“XPG4.2”) and IEEE Std 1003.1-2004
(“POSIX.1”) (XSI extension).
HISTORY
The functions endgrent
(),
getgrent
(), getgrgid
(),
getgrnam
(), and setgrent
()
appeared in Version 7 AT&T UNIX. The
functions setgrfile
() and
setgroupent
() appeared in
4.3BSD-Reno. The functions
getgrgid_r
() and
getgrnam_r
() appeared in NetBSD
3.0.
BUGS
The functions getgrent
(),
getgrgid
(), getgrnam
(),
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.
getgrent
() makes no attempt to suppress duplicate
information if multiple sources are specified in
nsswitch.conf(5)