setnetgrent(3) — Linux manual page


SETNETGRENT(3)          Linux Programmer's Manual         SETNETGRENT(3)

NAME         top

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

SYNOPSIS         top

       #include <netdb.h>

       int setnetgrent(const char *netgroup);
       void endnetgrent(void);

       int getnetgrent(char **restrict host,
                   char **restrict user, char **restrict domain);
       int getnetgrent_r(char **restrict host,
                   char **restrict user, char **restrict domain,
                   char *restrict 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

       setnetgrent(), endnetgrent(), getnetgrent(), getnetgrent_r(),
           Since glibc 2.19:
           Glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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         top

       These functions return 1 on success and 0 for failure.

FILES         top


ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │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         top

       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

NOTES         top

       In the BSD implementation, setnetgrent() returns void.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.13 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

GNU                            2021-03-22                 SETNETGRENT(3)

Pages that refer to this page: getent(1)