Question

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?

Answer 1

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);
}