NAME
getgrent,
getgrnam, getgrgid,
setgroupent, setgrent,
endgrent —
group database operations
SYNOPSIS
#include
<grp.h>
struct group *
getgrent(void);
struct group *
getgrnam(const
char *name);
struct group *
getgrgid(gid_t
gid);
struct group *
setgroupent(int
stayopen);
int
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.
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 routines 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 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 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 the group entry if successful; if end-of-file is reached
or an error occurs a null pointer is returned. The functions
setgroupent() and setgrent()
return the value 1 if successful, otherwise the value 0 is returned. The
functions endgrent() and
setgrfile() have no return value.
FILES
- /etc/group
- group database file
SEE ALSO
getpwent(3),
group(5)
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.
COMPATIBILITY
The historic function setgrfile(), which
allowed the specification of alternate password 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.