differentiate between file and pipe.

makefile

@@ -28,3 +28,6 @@ build: $(SRC)
 
 format: $(SRC)
 	$(FORMATTER) $(SRC)
+
+test: $(OUTPUT)
+	/bin/echo -e "123\n45 67" | ./$(OUTPUT)

wc.c

@@ -1,10 +1,23 @@
-#include <unistd.h>
 #include <stdio.h>
+#include <unistd.h> // read, isatty
 
-int main(){
+// STDIN_FILENO
+int process_fp(FILE* fp)
+{
     char buffer[1];
-	while(read(0,buffer,sizeof(buffer)) > 0){
+    while (read(0, buffer, sizeof(buffer)) > 0) {
         printf("%c", buffer[0]);
     }
 		return 0;
 }
+
+int main(int argc, char** argv)
+{
+    //
+    if (!isatty(STDIN_FILENO)) { // check if stdin is coming from terminal or pipeline
+        return process_fp(STDIN_FILENO);
+    } else if(argc > 1){
+			printf("To do");
+		}
+    return 0;
+}