endgrent(3p) — Linux manual page


ENDGRENT(3P)            POSIX Programmer's Manual           ENDGRENT(3P)

PROLOG         top

       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.

NAME         top

       endgrent, getgrent, setgrent — group database entry functions

SYNOPSIS         top

       #include <grp.h>

       void endgrent(void);
       struct group *getgrent(void);
       void setgrent(void);

DESCRIPTION         top

       The getgrent() function shall return a pointer to a structure
       containing the broken-out fields of an entry in the group
       database. If the group database is not already open, getgrent()
       shall open it and return a pointer to a group structure
       containing the first entry in the 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 so that
       the next getgrent() call returns the first entry, allowing
       repeated searches.

       The endgrent() function shall close the group database.

       The setgrent() and endgrent() functions shall not change the
       setting of errno if successful.

       On error, the setgrent() and endgrent() functions shall set errno
       to indicate the error.

       Since no value is returned by the setgrent() and endgrent()
       functions, an application wishing to check for error situations
       should set errno to 0, then call the function, then check errno.

       These functions need not be thread-safe.

RETURN VALUE         top

       On successful completion, getgrent() shall return a pointer to a
       group structure. On end-of-file, getgrent() shall return a null
       pointer and shall not change the setting of errno.  On error,
       getgrent() shall return a null pointer and errno shall 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 getgrent().  The returned pointer, and
       pointers within the structure, might also be invalidated if the
       calling thread is terminated.

ERRORS         top

       These functions may fail if:

       EINTR  A signal was caught during the operation.

       EIO    An I/O error has occurred.

       In addition, the getgrent() and setgrent() functions may fail if:

       EMFILE All file descriptors available to the process are
              currently open.

       ENFILE The maximum allowable number of files is currently open in
              the system.

       The following sections are informative.

EXAMPLES         top



       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.

RATIONALE         top




SEE ALSO         top

       endpwent(3p), getgrgid(3p), getgrnam(3p), getlogin(3p)

       The Base Definitions volume of POSIX.1‐2017, grp.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                      ENDGRENT(3P)

Pages that refer to this page: grp.h(0p)endpwent(3p)getgrent(3p)getgrgid(3p)getgrnam(3p)setgrent(3p)