reading a text file into an array in c

If mmap(2) is available on your system, you can open the file and map it into memory. That way, you have no memory to allocate, you even don't have to read the file, the system will do it. You can use the fseek() trick litb gave to get the size.

void *mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);

EDIT: You have to use lseek() to obtain the size of the file, .

int fd = open("filename", O_RDONLY);
int nbytes = lseek(fd, 0, SEEK_END);
void *content = mmap(NULL, nbytes, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);