C Strtok Segfaulting

Question

I'm not sure why the following code is segfaulting:

char * buffer = "SIZE";
char * tempString;
tempString = strtok(buffer, " ");
if(strcmp(tempString, "SIZE") == 0){    
    tempString = strtok(NULL, " ");           <----Faulting here
}

Since there is nothing left to tokenate shouldn't tempString just be equal to NULL? Thank you for any help in advance.

Answer 1

There are two problems:

First, strtok requires a modifiable string for the first parameter and buffer in your example is not. Try this instead:

char buffer[] = "SIZE";

Second, strcmp doesn't handle NULL which strtok can return:

if (NULL != tempString && strcmp(tempString, "SIZE") == 0)

Answer 2

Just go over the tokenized elements as the reference says , you have a clean approach if you follow it.

CORRECT CODE:

char buffer[] = "SIZE";
char * tok;
tok = strtok(buffer, " ");
while(tok != NULL)
{
  if(strcmp(tok, "SIZE") != 0)    
    break;
  tok = strtok(NULL, " ");        //   <----Faulted here
}

yes, it may skip multiple "SIZE" words in the buffer, so it does a bit more than what you originally did, but it is easier to read for an other programmer (and easier to recall it later, for you too).