setnetgrent(3)		    Library Functions Manual		  setnetgrent(3)

NAME
     setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr - handle net-
     work group entries

LIBRARY
     Standard C library (libc, -lc)

SYNOPSIS
     #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(size_t size;
		 char **restrict host,
		 char **restrict user, char **restrict domain,
		 char buf[restrict size], size_t size);

     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 subse-
     quent 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).
     allbox; lb lb lbx l l l.  Interface Attribute Value T{ setnetgrent(),
     getnetgrent_r(), innetgr() T}   Thread safety  T{ MT-Unsafe race:netgrent
     locale T} T{ endnetgrent() T}   Thread safety  T{ MT-Unsafe race:netgrent
     T} T{ getnetgrent() T}   Thread safety  T{ MT-Unsafe race:netgrent
     race:netgrentbuf locale T}

     In the above table, netgrent in race:netgrent signifies that if any of  the
     functions setnetgrent(), getnetgrent_r(), innetgr(), getnetgrent(), or end-
     netgrent()	 are  used  in	parallel in different threads of a program, then
     data races could occur.

VERSIONS
     In the BSD implementation, setnetgrent() returns void.

STANDARDS
     None.

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

SEE ALSO
     sethostent(3), setprotoent(3), setservent(3)

Linux man-pages 6.18		   2026-02-08			  setnetgrent(3)