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GETGRENT(3) FreeBSD Library Functions Manual GETGRENT(3)
NAME
getgrent, getgrent_r, getgrnam, getgrnam_r, getgrgid, getgrgid_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 bufsize,
struct group **result);
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);
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 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.
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 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 does not 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 identical to setgroupent() with an argument of
zero.
The endgrent() function closes any open files.
RETURN VALUES
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 getgrent_r(), getgrnam_r(), and getgrgid_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.)
The function setgroupent() returns the value 1 if successful, otherwise
the value 0 is returned. The functions endgrent(), setgrent() and
setgrfile() have no return value.
FILES
/etc/group group database file
COMPATIBILITY
The historic function setgrfile(), which allowed the specification of
alternate password databases, has been deprecated and is no longer
available.
SEE ALSO
getpwent(3), group(5), nsswitch.conf(5), yp(8)
STANDARDS
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.
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 functions getgrent_r(),
getgrnam_r(), and getgrgid_r() appeared in FreeBSD 5.1.
BUGS
The functions getgrent(), getgrnam(), getgrgid(), setgroupent() and
attempt to suppress duplicate information if multiple sources are
specified in nsswitch.conf(5).
FreeBSD 14.0-RELEASE-p6 July 31, 2016 FreeBSD 14.0-RELEASE-p6