Using fgetc to read words? - c

Question

I want to read a text file, character by character, and then do something with the characters and something with the words. This is my implementation:
char c;
char* word="";
fp = fopen("text.txt","rt");
do
{
c = (char)fgetc(fp);
if(c == ' ' || c == '\n' || c == '\0' || c == '\t')
{
//wordfunction(word)
word = ""; //Reset word
}
else
{
strcat(word, &c); //Keeps track of current word
}
//characterfunction(c);
}while(c != EOF);
fclose(fp);
However, when I try to run this my program instantly crashes. Is there a problem with setting word to ""? If so, what should I do instead?

Answer 1

In your word variable initial assignment, you're pointing to a static string of length 0. When you try to write data into there, you'll overwrite something else and your program will brake. You need, instead, to reserve space to your words.
where you have
char* word="";
use instead
char word[100];
This will create a space of 100 chars for your word.
char c;
char word[100];
fp = fopen("text.txt","rt");
int index = 0;
do {
c = (char)fgetc(fp);
if(c == ' ' || c == '\n' || c == '\0' || c == '\t') {
//wordfunction(word)
word[0] = 0; //Reset word
index = 0;
} else {
word[index++] = c;
word[index] = 0;
//strcat(word, &c); //Keeps track of current word
}
//characterfunction(c);
} while(c != EOF);
fclose(fp);

Answer 2

word points to a constant area which is not allowed to be write by strcat, so your code dumped;
word should have enough space to reserve chars, try hard-coded or realloc(word, size_t);
this can be compiled with gcc -o:
int main(){
char c;
char word[1000] = {0}; //enough space
FILE* fp = fopen("text.txt","rt");
int index = 0;
assert(0 != fp);
do
{
c = (char)fgetc(fp);
if(c == ' ' || c == '\n' || c == '\0' || c == '\t')
{
//wordfunction(word)
index = 0;
}
else
{
word[index++] = c;
}
//characterfunction(c);
}while(c != EOF);
word[index] = 0;
fclose(fp);
return 0;
}