I have this part in a code:
char* data="My name is: ";
I would like to add to this the argv[1] argument with represents a name. How to do this in c code? I've tried strcpy and strcat but i have segmentation fault when Ipcp do this:
strcpy(data,argv[1]);
Can anyone please help?
Also why this: data=data+argv[1] is not working?
You need to provide some memory, where the result of the concatentation can be stored into. For example:
char buffer[1024];
strcpy(buffer, "My name is: ");
strcat(buffer, argv[1]);
Note, however, that this is error prone: if the value of argv[1] combined with the prefix string is longer than 1024 characters, this produces a buffer overflow. So, maybe something like this:
char* prefix = "My name is: ";
int length = strlen(prefix) + strlen(argv[1]) + 1;
char* buffer = malloc(length);
if (!buffer) abort();
else
{
strcpy(buffer, prefix);
strcat(buffer, argv[1]);
/* Do something with buffer here. And don't
* forget to free it, once you no longer need
* it. This is C -- no garbage collection. */
free(buffer);
}
Memory for data will be allocated in read-only section. so modifying will cause issue.
where in memory are string literals ? stack / heap?
+ operator will not do concat as you thought.
strcat() function is implemented in string.h.
Also why this: data=data+argv[1] is not working?
About this one - in C data and argv are nothing more than pointers to address in the memory containing your string. You can't concatenate strings(char*) this way. I suggest to take a look at the string library and maybe a bit more in C as a whole.
You cant append to th data pointer because there are no space in it
char result_data [1024];
char* data="My name is: ";
strcat(result_data, data);
strcat(result_data, argv[1]);
