CODEWITHSUNDEEP
carraysstring
pato.llaguno
pato.llaguno

Reputation: 741

How to store CHAR array to string MAC ADDRESS

I have a function that returns a unsigned char chMAC[6]; which is the mac address and i print it out as 

printf("Mac: %x",chMAC[0]);
printf("%x",chMAC[1]);
printf("%x",chMAC[2]);
printf("%x",chMAC[3]);
printf("%x",chMAC[4]);
printf("%x\n",chMAC[5]);

And i get an output as Mac: B827E82D398E which is the actual mac address, but now i need to get that value as a string to pass to a sql parameter and i don't know how, since i need to add : in between. such as Mac: B8:27:E8:2D:39:8E

i bet this is easy, but i am still learning C.

Upvotes: 1

Views: 1801

Answers (3)

Erik Johnson
Erik Johnson

Reputation: 1164

You have all the pieces there, you just need to string them into the right order. Instead of using 6 separate printf() statements, pull it into one statement with all the formatting:

printf("Mac: %02X:%02X:%02X:%02X:%02X:%02X\n", 
             chMAC[0], chMAC[1], chMAC[2], chMAC[3], chMAC[4], chMAC[5]);

The "02" in the "%02X" formatting statements will put a leading zero if the value is <15; the capital X will make the alphabetic Hex digits into capitals (which is the usual convention when passing MAC addresses).

To send the resulting string to a buffer instead of to stdout, call sprintf (or even better, snprintf) with the same formatting string.

char mac_str[24];
snprintf(mac_str, sizeof(mac_str), "Mac: %02X:%02X:%02X:%02X:%02X:%02X\n", 
              chMAC[0], chMAC[1], chMAC[2], chMAC[3], chMAC[4], chMAC[5]);

Upvotes: 3

Marc B
Marc B

Reputation: 360692

why all the separate calls?

newlength = sprintf(mac, '%x:%x:%x:%x:%x:%x\n', chMAC[1], etc....)

You can have multiple %whatever format characters in a single printf/sprintf call...

Upvotes: 0

Doug Currie
Doug Currie

Reputation: 41180

You probably want all the bytes to be displayed as two characters:

%2x

but with a leading 0 instead of space:

%02x

You can string this all together in one printf call

printf("Mac: %02X:%02X:%02X:%02X:%02X:%02X\n"
       , chMAC[0], chMAC[1], chMAC[2], chMAC[3], chMAC[4], chMAC[5]);

If you want the text to go to a sting buffer instead of stdout do this:

char buffer[32];

snprintf(buffer, sizeof(buffer)
        , "Mac: %02X:%02X:%02X:%02X:%02X:%02X\n"
        , chMAC[0], chMAC[1], chMAC[2], chMAC[3], chMAC[4], chMAC[5]);

Upvotes: 3

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