enter.c

#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[])
{
	/* Real file path */
	char *filepath = argc[argv-1];

	/* check .txt file */
	char *type = &filepath[strlen(filepath) -4];

	if (strcmp(type, ".txt") != 0)
	{
		printf("No .txt file get. Exit!\n\nUsage: Drag any .txt file to it.\n");
#ifdef __WINDOWS_
		system("pause");
#endif
		return 0;
	}

	/* new file path */
	char newpath[10000];
	strcpy(newpath, filepath);
	newpath[strlen(newpath)-4] = '\0';
	strcat(newpath, "enter.txt");

	FILE *fp = fopen(filepath, "r");
	FILE *new = fopen(newpath, "w");
	char s[100];
	int i=0;
	while (fgets(s, 99, fp) != NULL )
	{
		if (*s != '\n')
		{
			fprintf(new, "%s\n", s);
		}
		else 
		{
			i++;
			if (i > 1) fprintf(new, "\n");
		}
	}
	fclose(fp);
	fclose(new);

	return 0;
}