Hi i am trying to figure out how to copy only part of a line being read from a text file. I want to copy a line from a file called fileLine to a variable called line. The problem is, is that i only want to copy starting at index 10 in fileLine but memcpy dislikes that. How can i change this to make memcpy happy?
int stringLength = 0;
stringLength = strlen(fileLine);
memcpy(line, fileLine[10], stringLength); //this is where things go wrong.
You have passed in a char type to something that expected a const void*. This would have been okay if you had passed it a char*. You can do that as either &fileLine[10] or fileLine + 10.
Since you are offsetting by 10, you also want to ensure you copy 10 fewer characters:
memcpy(line, &fileLine[10], stringLength-10);
Although you probably want to copy the string terminator too...
memcpy(line, &fileLine[10], stringLength-9);
Yuck!
Instead, you could use strcpy:
strcpy(line, fileLine + 10);
In all cases, make sure that line is an array or a pointer to memory that is actually allocated to your process.
You can use getline function to get part of the string. But first, you have to move your read pointer to the position from which you want to read using seekg function. seekg(ios flag, bytes); cin.getline(source, number of characters, ending character);
memcpy(line, &fileLine[10], stringLength-10);strcpy()so you don't risk running off the end of the string:strcpy(line, &fileLine[10]);- or usestringLength = strlen(fileLine) - 10;if you insist onmemcpy().