Question

I tried to use sprintf to append a int, string and an int.

sprintf(str,"%d:%s:%d",count-1,temp_str,start_id);

Here, the value of start_id is always the same. The value of temp_str which is a char * increases every time. I get correct output for some time and then my sprintf starts printing junk characters between temp_str and startid. So my str get corrupted.

Can anyone explain this behavior ?

example

at count 11

11:1:2:3:1:2:3:1:2:3:1:21:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2

at count 8

8:1:2:3:1:2:3:1:2:3:1:21:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1:2:3:1�:2

I don’t understand why and how “�” is appended to the string

Answer 1

1> try to memset your str buffer with 0 befor using sprintf

2> The value of temp_str which is a char * increases every time
what do u mean by this ?

this should be normal charachter pointer which will point some string and that string should be null terminated and tha will be copied to str

3> the total size by combing all three argument should not be exceed the size of str buffer