setnetgrent, endnetgrent, getnetgrent, getnetgrent_r, innetgr - handle network
group entries
#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
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.
These functions return 1 on success and 0 for failure.
/etc/netgroup
/etc/nsswitch.conf
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
setnetgrent (), getnetgrent_r (), innetgr () |
Thread safety |
MT-Unsafe race:netgrent locale |
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.
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.
In the BSD implementation,
setnetgrent() returns void.
sethostent(3),
setprotoent(3),
setservent(3)