Segfault in parsing char* into tokens - c

Question

I'm trying to parse a string around an arbitrary index. In my simplest test program I could come up with I have an input string I read the input into and then do memcpy to parse the string.
For testing this I am typing in "this text" as input. readInput is a function where I just have it calling getline(&input, &size, stdnin) and return the input pointer.
int main(){
char *input;
input = readInput();
int parseAround = 4;
char *token1;
char *token2;
memcpy(token1, inputBuffer, 4);
printf("token: %s\n", token1); //prints "this"
memcpy(token1, inputBuffer + (parseAround+1), 4);
//when changed to memcpy(token2,...); segfaults
printf("token: %s\n", token1); //prints "text"
free(input);
return 0;
}
However when I change the second memcpy to use token2 rather than token1, I get a segmentation fault. Why is this?

Answer 1

You most likely need to allocate memory for token1.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(){
char *input = NULL;
size_t len = 0;
ssize_t read;
/* Read in the line "Hello world" */
read = getline(&input, &len, stdin);
printf("Retrieved line of length %zu :\n", read);
printf("%s", input);
/* Allocate memory for both parts of the string */
char *token1 = malloc((read+1) * sizeof(char *));
char *token2 = malloc((read+1) * sizeof(char *));
memcpy(token1, input, 6);
printf("token: %s\n", token1); //prints "Hello"
memcpy(token2, (input+6), 5);
printf("token: %s\n", token2); //prints "world"
free(input);
return 0;
}
Read in the line, allocate memory for each string part, and then copy the part you want into your s