Convert hexadecimal value to ip address of type string in C.

Question

i have a hex value say for example 0x0a010203 and i want to convert it to a string such that after conversion it should be like "10.1.2.3",How to extract the individual fields from the hex value ?

you can use loop extract non-zero number one by one,then turn it into decimal number.or you can use library function combination to solve your problem. — Nibnat, May 10 '14 at 06:19

score 5 · Answer 1 · answered May 10 '14 at 06:22

5

You can use bit masking and bit shifts, eg:

unsigned int val = 0x0a010203;
printf("%d.%d.%d.%d",
     (val & 0xFF000000) >> 24,
     (val & 0x00FF0000) >> 16,
     (val & 0x0000FF00) >> 8,
     val & 0x000000FF);

answered May 10 '14 at 06:22

jkyako

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Martin R · Accepted Answer · 2014-05-10T06:37:44.427

4

Fill a struct in_addr and use inet_ntoa() ("Internet address to ASCII string"):

#include <arpa/inet.h>

struct in_addr addr;
addr.s_addr = htonl(0x0a010203); // s_addr must be in network byte order 
char *s = inet_ntoa(addr); // --> "10.1.2.3"

Note that the string returned by inet_ntoa() may point to static data that may be overwritten by subsequent calls. That is no problem if it is just printed and then not used anymore. Otherwise it would be necessary to duplicate the string.

edited May 10 '14 at 06:37

answered May 10 '14 at 06:22

Martin R

529,903
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Is there a similar method for IPv6? – Athul Sukumaran Nov 27 '20 at 11:44
@AthulSukumaran: `inet_ntop` or `getnameinfo`. See https://stackoverflow.com/a/20130662/1187415 for an example. – Martin R Nov 27 '20 at 12:08
Thanks @Martin. But for ipv6, in6_addr stores value as unsigned char[16]. inet_ntop expects this as argument. My question was specifically about hex value. Also htonl doesn't seem to work for such large hex. – Athul Sukumaran Nov 27 '20 at 12:18

Convert hexadecimal value to ip address of type string in C.

2 Answers2