getnetent_r, getnetbyname_r, getnetbyaddr_r - get network entry (reentrant)


#include <netdb.h>

int getnetent_r(struct netent *result_buf, char *buf,
 size_t buflen, struct netent **result,
 int *h_errnop);

int getnetbyname_r(const char *name,
 struct netent *result_buf, char *buf,
 size_t buflen, struct netent **result,
 int *h_errnop);

int getnetbyaddr_r(uint32_t net, int type,
 struct netent *result_buf, char *buf,
 size_t buflen, struct netent **result,
 int *h_errnop);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

getnetent_r(), getnetbyname_r(), getnetbyaddr_r(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE || _SVID_SOURCE


The getnetent_r(), getnetbyname_r(), and getnetbyaddr_r() functions are the reentrant equivalents of, respectively, getnetent(3), getnetbyname(3), and getnetbynumber(3). They differ in the way that the netent structure is returned, and in the function calling signature and return value. This manual page describes just the differences from the nonreentrant functions.

Instead of returning a pointer to a statically allocated netent structure as the function result, these functions copy the structure into the location pointed to by result_buf.

The buf array is used to store the string fields pointed to by the returned netent structure. (The nonreentrant functions allocate these strings in static storage.) The size of this array is specified in buflen. If buf is too small, the call fails with the error ERANGE, and the caller must try again with a larger buffer. (A buffer of length 1024 bytes should be sufficient for most applications.)

If the function call successfully obtains a network record, then *result is set pointing to result_buf; otherwise, *result is set to NULL.

The buffer pointed to by h_errnop is used to return the value that would be stored in the global variable h_errno by the nonreentrant versions of these functions.


On success, these functions return 0. On error, they return one of the positive error numbers listed in ERRORS.

On error, record not found (getnetbyname_r(), getnetbyaddr_r()), or end of input (getnetent_r()) result is set to NULL.



(getnetent_r()) No more records in database.


buf is too small. Try again with a larger buffer (and increased buflen).


For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
getnetent_r(), getnetbyname_r(), getnetbyaddr_r() Thread safety MT-Safe locale


These functions are GNU extensions. Functions with similar names exist on some other systems, though typically with different calling signatures.


getnetent(3), networks(5)


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