CODEWITHSUNDEEP
c
blitz
blitz

Reputation: 84

joining strings with a delimiter between them in c

I'm trying to combine two strings with a delimiter between them using strncat but i'm not able to get the exact results .Please let me know why is it getting wrong .

  #include <stdio.h>
  #include <string.h>

  int main()
  { 
     char Buff[100];
     memset(Buff,0,sizeof(Buff));
     char *Ip="192.168.4.10";
     char *Ip2="192.168.4.20";
     strcpy(Buff,Ip);

     strncat(Buff,"||",sizeof("||"));

     strncat(Buff,Ip2,sizeof(Ip2));
     printf("%s",Buff);


  }

I'm getting the output as 192.168.4.10||192. instead of the concatenation of the two data.What could have gone wrong . Is there still more efficient way of doing this ?

Upvotes: 0

Views: 189

Answers (1)

Grijesh Chauhan
Grijesh Chauhan

Reputation: 58281

The expression strncat(Buff,Ip2, sizeof(Ip2)); is wrong because sizeof(Ip2) gives size of Ip2 pointer but not length of string pointed by Ip2.

In your system size of char pointer is 4 bytes that is why strncat() could append only 4 chars from string Ip2 (1, 9, 2, .).

You are confuse between sizeof() operator and length of string. Note sizeof("||") gives you 3 ( that is number of bytes "||" takes) while it's length is 2.

Additionally, the first strncat(Buff,"||",sizeof("||")); working well because third char is \0.

To rectify your code use strlen(char *) function from string.h header file: 

strncat(Buff, "||", strlen("||"));
strncat(Buff, Ip2, strlen(Ip2));

Check this working code

Upvotes: 2

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