GETGRENT(3) BSD Library Functions Manual GETGRENT(3)NAME
getgrent, getgrent_r, getgrgid, getgrgid_r, getgrnam, getgrnam_r,
setgroupent, setgrent, endgrent — group database operations
LIBRARY
Standard C Library (libc, -lc)
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, signifi‐
cantly speeding functions subsequent calls. This functionality is unnec‐
essary 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 occured. If an error occured, the global vari‐
able 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 avail‐
able.
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 and buflen
Other errno values may be set depending on the specific database back‐
ends.
SEE ALSOgetpwent(3), group(5), nsswitch.conf(5)STANDARDS
The getgrgid() and getgrnam() functions conform to ISO/IEC 9945-1:1990
(“POSIX.1”). The getgrgid_r() and getgrnam_r() functions conform to IEEE
Std 1003.1c-1995 (“POSIX.1”). 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 mod‐
ify the same object.
The functions getgrent(), endgrent(), setgroupent(), and setgrent() are
fairly useless in a networked environment and should be avoided, if pos‐
sible. getgrent() makes no attempt to suppress duplicate information if
multiple sources are specified in nsswitch.conf(5)BSD April 30, 2008 BSD
