Determining necessary array length to store input

Question

What's the best way to determine the length of an input stream in Stdin so that you can create an array of the correct length to store it using, say, getchar()?

Is there some way of peeking at all the characters in the input stream and using something like:

while((ch = readchar()) != "\n" ) {
    count++;
}

and then creating the array with size count?

Answer 1

During the time I typed the code, there are several similar answers. I am afraid you will need to do something like:

int  size = 1;
char *input = malloc(size);
int  count = 0;
while((ch = getchar()) != '\n' ) {
    input[count++] = ch;
    if (count >= size) {
         size = size * 2;
         input = realloc(input, size);
    }
}
input[count++] = 0;
input = realloc(input, count);

Alternatively you can use the same as a POSIX library function getline(). I.e.

int count, size;
char *input = NULL;
count = getline(&input, &size, stdin);

In both cases, do not forget to free input once you have finished with it.