couple things missing but meh its there mostly

334/homework/3/msh.c

@@ -1,24 +1,47 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/types.h>
 
 #define PROMPT "msh> "
 #define EXIT_CMD "exit"
 #define MAX_BUF 121
 
+// Statuses from builtin responses
+#define RESP_HELP 1
+#define RESP_DATE 2
+#define RESP_ECHO 3
+#define RESP_SHELL 4
+
 void echo(const char*);
 void remove_newline(char*);
 void exit_branch(const char*);
+int  builtin_response(char*);
+
 
 int main(void) {
 	char buffer[MAX_BUF];
 	while(1) {
 		printf("%s", PROMPT);
 		fgets(buffer, MAX_BUF, stdin);
-		// process the input
-		remove_newline(buffer);
+		// Deal with EOF input
+		if(!strlen(buffer)) {
+			exit(0);
+		}
 		exit_branch(buffer);
-		echo(buffer);
+
+		remove_newline(buffer);
+		int status = builtin_response(buffer);
+		// the switch in case we need to add more response flags later
+		switch(status) {
+			case RESP_ECHO: 
+				echo(buffer);
+			case RESP_SHELL: // shell command handler was used
+				continue;
+		}
+		memset(buffer, 0x00, MAX_BUF); // reset buffer after each usage
 	}
 	return 0;
 }
@@ -35,9 +58,51 @@ void remove_newline(char* buf) {
 }
 
 void exit_branch(const char* buf) {
-	if(strcmp(buf, EXIT_CMD)) {
-		return;
+	if(!strcmp(buf, EXIT_CMD)) {
+		exit(0);
 	}
-	exit(0);
-	return; // just for gcc but exit shouldn't fail
+}
+
+int builtin_response(char* buffer) {
+#define STRING_DELIMITER " "
+#define TIME_FMT "%D"
+	exit_branch(buffer);	// exit is builtin so here we are
+	if(!strcmp(buffer, "help")) {
+		echo("enter Linux commands, or ‘exit’ to exit");
+		return RESP_HELP;
+	}
+
+	// Printout the date today
+	if(!strcmp(buffer, "date")) {
+		static char date[64];
+		time_t now = time(0);
+		strftime(date, sizeof(date), TIME_FMT, localtime(&now));
+		echo(date);
+		return RESP_DATE;
+	}
+
+	char *tokens[64];
+	int idx = 0;
+	for(char* cur = strtok(buffer, STRING_DELIMITER); cur != NULL; cur=strtok(NULL, STRING_DELIMITER)) { 
+#ifdef DBG_LINE
+		printf("%s ", cur);
+#endif
+		tokens[idx] = cur;
+		idx++;
+	}
+
+	// Execute child process
+	pid_t child = fork();
+	if(child) {
+		int status_child = wait(NULL);
+		if(status_child == 127) {
+			echo("command not found: oh btw remember to not print this string kek");
+		}
+	}
+	execvp(tokens[0], tokens);
+	// Cleanup pointers
+	for(int i = 0; i< 64; i++) {
+		tokens[i] = NULL;
+	}
+
 }