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SETNETGRENT(3)             Linux Programmer's Manual            SETNETGRENT(3)
NAME
       setnetgrent,  endnetgrent, getnetgrent, getnetgrent_r, innetgr - handle
       network group entries
SYNOPSIS
       #include <netdb.h>
       int setnetgrent(const char *netgroup);
       void endnetgrent(void);
       int getnetgrent(char **host, char **user, char **domain);
       int getnetgrent_r(char **host, char **user,
                         char **domain, char *buf, size_t buflen);
       int innetgr(const char *netgroup, const char *host,
                   const char *user, const char *domain);
   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
       setnetgrent(), endnetgrent(), getnetgrent(), getnetgrent_r(),
       innetgr():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
       The  netgroup  is  a SunOS invention.  A netgroup database is a list of
       string triples  (hostname,  username,  domainname)  or  other  netgroup
       names.   Any of the elements in a triple can be empty, which means that
       anything matches.  The functions described here  allow  access  to  the
       netgroup  databases.  The file /etc/nsswitch.conf defines what database
       is searched.
       The setnetgrent() call defines the netgroup that will  be  searched  by
       subsequent  getnetgrent()  calls.  The getnetgrent() function retrieves
       the next netgroup entry, and returns pointers in host, user, domain.  A
       null  pointer  means  that  the corresponding entry matches any string.
       The pointers are valid only as long as there is no call to  other  net-
       group-related  functions.   To  avoid  this problem you can use the GNU
       function getnetgrent_r() that stores the strings in the  supplied  buf-
       fer.  To free all allocated buffers use endnetgrent().
       In  most  cases  you want to check only if the triplet (hostname, user-
       name, domainname) is a member of a netgroup.   The  function  innetgr()
       can be used for this without calling the above three functions.  Again,
       a null pointer is a wildcard and matches any string.  The  function  is
       thread-safe.
RETURN VALUE
       These functions return 1 on success and 0 for failure.
FILES
       /etc/netgroup
       /etc/nsswitch.conf
ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).
       +-----------------+---------------+-------------------------+
       |Interface        | Attribute     | Value                   |
       +-----------------+---------------+-------------------------+
       |setnetgrent(),   | Thread safety | MT-Unsafe race:netgrent |
       |getnetgrent_r(), |               | locale                  |
       |innetgr()        |               |                         |
       +-----------------+---------------+-------------------------+
       |endnetgrent()    | Thread safety | MT-Unsafe race:netgrent |
       +-----------------+---------------+-------------------------+
       |getnetgrent()    | Thread safety | MT-Unsafe race:netgrent |
       |                 |               | race:netgrentbuf locale |
       +-----------------+---------------+-------------------------+
       In the above table, netgrent in race:netgrent signifies that if any  of
       the functions setnetgrent(), getnetgrent_r(), innetgr(), getnetgrent(),
       or endnetgrent() are used in parallel in different threads  of  a  pro-
       gram, then data races could occur.
CONFORMING TO
       These  functions  are not in POSIX.1, but setnetgrent(), endnetgrent(),
       getnetgrent(), and innetgr() are available on most UNIX systems.   get-
       netgrent_r() is not widely available on other systems.
NOTES
       In the BSD implementation, setnetgrent() returns void.
SEE ALSO
       sethostent(3), setprotoent(3), setservent(3)
COLOPHON
       This  page  is  part of release 4.15 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.
GNU                               2017-09-15                    SETNETGRENT(3)