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GETGRENT(3)              BSD Library Functions Manual              GETGRENT(3)

NAME
     getgrent, getgrnam, getgrnam_r, getgrgid, getgrgid_r, getgruuid, getgruuid_r, setgroupent, setgrent,
     endgrent -- group database operations

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <grp.h>
     #include <uuid/uuid.h>

     struct group *
     getgrent(void);

     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
     getgruuid(uuid_t uuid);

     int
     getgruuid_r(uuid_t uuid, struct group *grp, char *buffer, size_t bufsize, struct group **result);

     int
     setgroupent(int stayopen);

     void
     setgrent(void);

     void
     endgrent(void);

DESCRIPTION
     These functions obtain information from opendirectoryd(8), including records in /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(), getgrgid(), and getgruuid() search the group database for the given group
     name pointed to by name, the group id given by gid, or the UUID given by uuid respectively, returning
     the first one encountered.  Identical group names, group gids, or uuids may result in undefined behav-ior. behavior.
     ior.

     Note that the groups file /etc/group does not contain group UUIDs.  The UUID for a group may be found
     using mbr_gid_to_uuid().

     On Mac OS X, these routines are thread-safe and return a pointer to a thread-specific data structure.
     The contents of this data structure are automatically released by subsequent calls to any of these rou-tines routines
     tines on the same thread, or when the thread exits.  These routines are therefore unsuitable for use in
     libraries or frameworks, from where they may overwrite the per-thread data that the calling application
     expects to find as a result of its own calls to these routines. Library and framework code should use
     the alternative reentrant variants detailed below.

     The getgrent() function sequentially reads the group database and is intended for programs that wish to
     step through the complete list of groups.

     The functions getgrnam_r(), getgrgid_r(), and getgruuid_r() are alternative versions of getgrnam(),
     getgrgid(), and getgruuid() respectively.  The caller must provide storage for the results of the
     search in the grp, 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, nonzero,
     zero, file descriptors are left open, significantly speeding functions subsequent calls.  This func-tionality functionality
     tionality 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 getgrnam_r(), getgrgid_r(),
     and getgruuid_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.)

     setgroupent() returns the value 1 if successful, otherwise the value 0 is returned.  The functions
     setgrent(), endgrent(), and setgrfile() have no return value.

FILES
     /etc/group  group database file

COMPATIBILITY
     The historic function setgrfile(), which allowed the specification of alternate group databases, has
     been deprecated and is no longer available.

SEE ALSO
     getpwent(3), group(5), mbr_gid_to_uuid(3,) opendirectory(8), 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 getgrnam_r()
     and getgrgid_r() appeared in FreeBSD 5.1.  The functions getgruuid() and getgruuid_r() appeared in Mac
     OS X 10.8.

BUGS
     The functions getgrent(), getgrnam(), getgrgid(), getgruuid(), setgroupent() and setgrent() leave their
     results in an internal thread-specific memory and return a pointer to that object.  Subsequent calls to
     the same function will modify the same object.

BSD                            October 26, 2011                            BSD

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