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15 | .\" California, Berkeley and its contributors. |
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30 | .\" SUCH DAMAGE. |
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31 | .\" |
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32 | .\" From: @(#)inet.3 8.1 (Berkeley) 6/4/93 |
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33 | .\" $Id$ |
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34 | .\" |
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35 | .Dd June 17, 1996 |
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36 | .Dt INET 3 |
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37 | .Os BSD 4.2 |
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38 | .Sh NAME |
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39 | .Nm inet_aton , |
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40 | .Nm inet_addr , |
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41 | .Nm inet_network , |
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42 | .Nm inet_ntoa , |
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43 | .Nm inet_makeaddr , |
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44 | .Nm inet_lnaof , |
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45 | .Nm inet_netof |
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46 | .Nd Internet address manipulation routines |
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47 | .Sh SYNOPSIS |
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48 | .Fd #include <sys/types.h> |
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49 | .Fd #include <sys/socket.h> |
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50 | .Fd #include <netinet/in.h> |
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51 | .Fd #include <arpa/inet.h> |
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52 | .Ft int |
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53 | .Fn inet_aton "const char *cp" "struct in_addr *pin" |
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54 | .Ft unsigned long |
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55 | .Fn inet_addr "const char *cp" |
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56 | .Ft unsigned long |
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57 | .Fn inet_network "const char *cp" |
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58 | .Ft char * |
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59 | .Fn inet_ntoa "struct in_addr in" |
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60 | .Ft struct in_addr |
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61 | .Fn inet_makeaddr "unsigned long net" "unsigned long lna" |
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62 | .Ft unsigned long |
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63 | .Fn inet_lnaof "struct in_addr in" |
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64 | .Ft unsigned long |
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65 | .Fn inet_netof "struct in_addr in" |
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66 | .Sh DESCRIPTION |
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67 | The routines |
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68 | .Fn inet_aton , |
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69 | .Fn inet_addr |
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70 | and |
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71 | .Fn inet_network |
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72 | interpret character strings representing |
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73 | numbers expressed in the Internet standard |
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74 | .Ql \&. |
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75 | notation. |
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76 | The |
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77 | .Fn inet_aton |
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78 | routine interprets the specified character string as an Internet address, |
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79 | placing the address into the structure provided. |
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80 | It returns 1 if the string was successfully interpreted, |
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81 | or 0 if the string is invalid. |
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82 | The |
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83 | .Fn inet_addr |
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84 | and |
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85 | .Fn inet_network |
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86 | functions return numbers suitable for use |
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87 | as Internet addresses and Internet network |
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88 | numbers, respectively. |
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89 | The routine |
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90 | .Fn inet_ntoa |
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91 | takes an Internet address and returns an |
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92 | .Tn ASCII |
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93 | string representing the address in |
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94 | .Ql \&. |
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95 | notation. The routine |
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96 | .Fn inet_makeaddr |
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97 | takes an Internet network number and a local |
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98 | network address and constructs an Internet address |
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99 | from it. The routines |
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100 | .Fn inet_netof |
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101 | and |
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102 | .Fn inet_lnaof |
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103 | break apart Internet host addresses, returning |
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104 | the network number and local network address part, |
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105 | respectively. |
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106 | .Pp |
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107 | All Internet addresses are returned in network |
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108 | order (bytes ordered from left to right). |
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109 | All network numbers and local address parts are |
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110 | returned as machine format integer values. |
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111 | .Sh INTERNET ADDRESSES |
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112 | Values specified using the |
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113 | .Ql \&. |
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114 | notation take one |
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115 | of the following forms: |
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116 | .Bd -literal -offset indent |
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117 | a.b.c.d |
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118 | a.b.c |
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119 | a.b |
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120 | a |
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121 | .Ed |
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122 | .Pp |
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123 | When four parts are specified, each is interpreted |
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124 | as a byte of data and assigned, from left to right, |
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125 | to the four bytes of an Internet address. Note |
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126 | that when an Internet address is viewed as a 32-bit |
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127 | integer quantity on the |
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128 | .Tn VAX |
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129 | the bytes referred to |
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130 | above appear as |
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131 | .Dq Li d.c.b.a . |
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132 | That is, |
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133 | .Tn VAX |
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134 | bytes are |
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135 | ordered from right to left. |
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136 | .Pp |
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137 | When a three part address is specified, the last |
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138 | part is interpreted as a 16-bit quantity and placed |
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139 | in the right-most two bytes of the network address. |
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140 | This makes the three part address format convenient |
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141 | for specifying Class B network addresses as |
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142 | .Dq Li 128.net.host . |
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143 | .Pp |
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144 | When a two part address is supplied, the last part |
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145 | is interpreted as a 24-bit quantity and placed in |
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146 | the right most three bytes of the network address. |
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147 | This makes the two part address format convenient |
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148 | for specifying Class A network addresses as |
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149 | .Dq Li net.host . |
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150 | .Pp |
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151 | When only one part is given, the value is stored |
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152 | directly in the network address without any byte |
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153 | rearrangement. |
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154 | .Pp |
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155 | All numbers supplied as |
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156 | .Dq parts |
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157 | in a |
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158 | .Ql \&. |
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159 | notation |
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160 | may be decimal, octal, or hexadecimal, as specified |
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161 | in the C language (i.e., a leading 0x or 0X implies |
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162 | hexadecimal; otherwise, a leading 0 implies octal; |
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163 | otherwise, the number is interpreted as decimal). |
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164 | .Pp |
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165 | The |
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166 | .Fn inet_aton |
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167 | and |
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168 | .Fn inet_ntoa |
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169 | functions are semi-deprecated in favor of the |
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170 | .Xr addr2ascii 3 |
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171 | family. However, since those functions are not yet widely implemented, |
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172 | portable programs cannot rely on their presence and will continue |
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173 | to use the |
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174 | .Xr inet 3 |
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175 | functions for some time. |
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176 | .Sh DIAGNOSTICS |
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177 | The constant |
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178 | .Dv INADDR_NONE |
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179 | is returned by |
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180 | .Fn inet_addr |
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181 | and |
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182 | .Fn inet_network |
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183 | for malformed requests. |
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184 | .Sh SEE ALSO |
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185 | .Xr addr2ascii 3 , |
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186 | .Xr gethostbyname 3 , |
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187 | .Xr getnetent 3 , |
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188 | .Xr hosts 5 , |
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189 | .Xr networks 5 |
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190 | .Sh HISTORY |
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191 | These |
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192 | functions appeared in |
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193 | .Bx 4.2 . |
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194 | .Sh BUGS |
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195 | The value |
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196 | .Dv INADDR_NONE |
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197 | (0xffffffff) is a valid broadcast address, but |
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198 | .Fn inet_addr |
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199 | cannot return that value without indicating failure. |
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200 | The newer |
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201 | .Fn inet_aton |
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202 | function does not share this problem. |
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203 | The problem of host byte ordering versus network byte ordering is |
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204 | confusing. |
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205 | The string returned by |
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206 | .Fn inet_ntoa |
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207 | resides in a static memory area. |
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208 | .Pp |
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209 | Inet_addr should return a |
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210 | .Fa struct in_addr . |
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