setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr - handle network group entries

       For an explanation of the terms used in this section, see attributes(7).
       ┌────────────────────────────┬───────────────┬──────────────────────────────────────────────────────────┐
       │ Interface                  │ Attribute     │ Value                                                    │
       ├────────────────────────────┼───────────────┼──────────────────────────────────────────────────────────┤
       │ setnetgrent(),             │ Thread safety │ MT-Unsafe race:netgrent locale                           │
       │ getnetgrent_r(), 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.

       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.

/etc/netgroup/etc/nsswitch.conf

setnetgrent(),   endnetgrent(),  getnetgrent(),  and  innetgr()  are  available  on  most  UNIX  systems.
       getnetgrent_r() is not widely available on other systems.

       Standard C library (libc, -lc)

       setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr - handle network group entries

       These functions return 1 on success and 0 for failure.

sethostent(3), setprotoent(3), setservent(3)

Linux man-pages 6.9.1                              2024-05-02                                     setnetgrent(3)

       None.

#include<netdb.h>intsetnetgrent(constchar*netgroup);voidendnetgrent(void);intgetnetgrent(char**restricthost,char**restrictuser,char**restrictdomain);intgetnetgrent_r(char**restricthost,char**restrictuser,char**restrictdomain,charbuf[restrict.buflen],size_tbuflen);intinnetgr(constchar*netgroup,constchar*host,constchar*user,constchar*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

       In the BSD implementation, setnetgrent() returns void.