| GETGRENT(3) | Library Functions Manual | GETGRENT(3) | 
getgrent, getgrent_r,
  getgrgid, getgrgid_r,
  getgrnam, getgrnam_r,
  setgroupent, setgrent,
  endgrent —
#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);
<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.
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.
setgrfile(), which allowed the
  specification of alternative group databases, has been deprecated and is no
  longer available.
getgrent, getgrent_r,
  getgrnam, getgrnam_r,
  getgrgid, getgrgid_r, and
  setgroupent:
EINTR]EIO]EMFILE]ENFILE]The following error code may be set in errno
    for getgrent_r, getgrnam_r,
    and getgrgid_r:
ERANGE]buffer and
      buflenOther errno values may be set depending on
    the specific database backends.
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).
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.
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)
| February 7, 2018 | NetBSD 10.0 |