The getgrent() function shall return a pointer to a structure containing
the broken-out fields of an entry in the group database. When first called,
getgrent() shall return a pointer to a group structure
containing the first entry in the group database. Thereafter, it shall return
a pointer to a group structure containing the next group structure in
the group database, so successive calls may be used to search the entire
An implementation that provides extended security controls may impose further
implementation-defined restrictions on accessing the group database. In
particular, the system may deny the existence of some or all of the group
database entries associated with groups other than those groups associated
with the caller and may omit users other than the caller from the list of
members of groups in database entries that are returned.
The setgrent() function shall rewind the group database to allow repeated
The endgrent() function may be called to close the group database when
processing is complete.
These functions need not be reentrant. A function that is not required to be
reentrant is not required to be thread-safe.
When first called, getgrent() shall return a pointer to the first group
structure in the group database. Upon subsequent calls it shall return the
next group structure in the group database. The getgrent() function
shall return a null pointer on end-of-file or an error and errno may be
set to indicate the error.
The return value may point to a static area which is overwritten by a subsequent
call to getgrgid(), getgrnam(), or getgrent().
These functions are provided due to their historical usage. Applications should
avoid dependencies on fields in the group database, whether the database is a
single file, or where in the file system name space the database resides.
Applications should use getgrnam() and getgrgid() whenever
possible because it avoids these dependencies.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html