Custom function to accept input of unknown length from a user. Can change the max size the buffer can grow to.

simple-readline.c

#define CHUNK_SIZE 256
#define MAX_CHUNKS 4
/**
 * Homemade readline. Dynamically read input.
 *
 * @param prompt The text to prefix the user's input with
 * @param line Assigned the value of the user's input if not NULL
 *
 * @return The size of the read input
 */
ssize_t readline(const char *prompt, char **line)
{
	if (prompt)
	{
		fputs(prompt, stdout);
	}

	*line = (char *) malloc(CHUNK_SIZE);
	size_t bufSize = CHUNK_SIZE;

	char    read;
	ssize_t pos = 0;
	while ((read = getchar()) != '\n' && bufSize < (CHUNK_SIZE * MAX_CHUNKS))
	{
		if ((int) read == EOF)
		{
			errno = 0;

			return -1;
		}

		(*line)[pos++] = read;

		if (pos == bufSize)
		{
			bufSize += CHUNK_SIZE;  // grow our buffer with extra padding in case
			*line = realloc(*line, bufSize);
		}
	}

	if (pos > 0)
	{
		// Shrink, but make room for \0
		*line = realloc(*line, (pos + 1));

		// dont forget to TERMINATE
		(*line)[pos] = '\0';
	}

	return pos;
}