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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd June 27, 2022 29.Dt GETNETENT 3 30.Os 31.Sh NAME 32.Nm getnetent , 33.Nm getnetbyaddr , 34.Nm getnetbyname , 35.Nm setnetent , 36.Nm endnetent 37.Nd get network entry 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In netdb.h 42.Ft struct netent * 43.Fn getnetent void 44.Ft struct netent * 45.Fn getnetbyname "const char *name" 46.Ft struct netent * 47.Fn getnetbyaddr "uint32_t net" "int type" 48.Ft void 49.Fn setnetent "int stayopen" 50.Ft void 51.Fn endnetent void 52.Ft int 53.Fn getnetent_r "struct netent *ne" "char *buffer" "size_t buflen" "struct netent **result" "int *h_errnop" 54.Ft int 55.Fn getnetbyaddr_r "uint32_t net" "int type" "struct netent *ne" "char *buffer" "size_t buflen" "struct netent **result" int *h_errorp" 56.Ft int 57.Fn getnetbyname_r "const char *name" "struct netent *ne" "char *buffer" "size_t buflen" "struct netent **result" "int *h_errorp" 58.Sh DESCRIPTION 59The 60.Fn getnetent , 61.Fn getnetbyname , 62and 63.Fn getnetbyaddr 64functions 65each return a pointer to an object with the 66following structure describing an internet network. 67This structure contains either the information obtained 68from the nameserver, broken-out fields of a line in the network data base 69.Pa /etc/networks , 70or entries supplied by the 71.Xr yp 8 72system. 73The order of the lookups is controlled by the 74`networks' entry in 75.Xr nsswitch.conf 5 . 76.Bd -literal -offset indent 77struct netent { 78 char *n_name; /* official name of net */ 79 char **n_aliases; /* alias list */ 80 int n_addrtype; /* net number type */ 81 uint32_t n_net; /* net number */ 82}; 83.Ed 84.Pp 85The members of this structure are: 86.Bl -tag -width n_addrtype 87.It Fa n_name 88The official name of the network. 89.It Fa n_aliases 90A zero terminated list of alternate names for the network. 91.It Fa n_addrtype 92The type of the network number returned; currently only AF_INET. 93.It Fa n_net 94The network number. 95Network numbers are returned in machine byte 96order. 97.El 98.Pp 99The 100.Fn getnetent 101function 102reads the next line of the file, opening the file if necessary. 103.Pp 104The 105.Fn setnetent 106function 107opens and rewinds the file. 108If the 109.Fa stayopen 110flag is non-zero, 111the net data base will not be closed after each call to 112.Fn getnetbyname 113or 114.Fn getnetbyaddr . 115.Pp 116The 117.Fn endnetent 118function 119closes the file. 120.Pp 121The 122.Fn getnetbyname 123function 124and 125.Fn getnetbyaddr 126sequentially search from the beginning 127of the file until a matching 128net name or 129net address and type is found, 130or until 131.Dv EOF 132is encountered. 133The 134.Fa type 135argument 136must be 137.Dv AF_INET . 138Network numbers are supplied in host order. 139.Pp 140Functions with the 141.Em _r 142suffix provide reentrant versions of their respective counterparts. 143The caller must supply five additional parameters: a 144.Vt struct netent 145variable to be filled on success, a 146.Va buffer 147of 148.Va buflen 149bytes in size, a 150.Vt struct netent 151.Va result 152variable that will point to the result on success or be set to 153.Dv NULL 154on failure or if the name is not found. 155The 156.Va h_errnop 157variable will be filled with the error code if any. 158All these functions return 0 on success. 159.Sh FILES 160.Bl -tag -width /etc/nsswitch.conf -compact 161.It Pa /etc/networks 162.It Pa /etc/nsswitch.conf 163.It Pa /etc/resolv.conf 164.El 165.Sh DIAGNOSTICS 166Null pointer returned on 167.Dv EOF 168or error. 169.Sh SEE ALSO 170.Xr networks 5 171.Pp 172.%T RFC 1101 173.Sh HISTORY 174The 175.Fn getnetent , 176.Fn getnetbyaddr , 177.Fn getnetbyname , 178.Fn setnetent , 179and 180.Fn endnetent 181functions appeared in 182.Bx 4.2 . 183.Sh BUGS 184The data space used by 185these functions is thread-specific; if future use requires the data, it should be 186copied before any subsequent calls to these functions overwrite it. 187Only Internet network 188numbers are currently understood. 189Expecting network numbers to fit 190in no more than 32 bits is probably 191naive. 192