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
       netgroup-related  functions.   To  avoid  this  problem  you  can  use  the  GNU  function
       getnetgrent_r()  that  stores  the  strings in the supplied buffer.  To free all allocated
       buffers use endnetgrent().

       In most cases you want to check only if the triplet (hostname, username, 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 program, 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.  getnetgrent_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/.