This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
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 database.
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
The endgrent() function may be called to close the group database
when processing is complete.
These functions need not 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 application shall not modify the structure to which the return
value points, nor any storage areas pointed to by pointers within the
structure. The returned pointer, and pointers within the structure,
might be invalidated or the structure or the storage areas might be
overwritten by a subsequent call to getgrgid(), getgrnam(), or
The getgrent() function may fail if:
EINTR A signal was caught during the operation.
EIO An I/O error has occurred.
EMFILE All file descriptors available to the process are currently
ENFILE The maximum allowable number of files is currently open in the
The following sections are informative.
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
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 ENDGRENT(3P)