update

Labs/Lab2/Makefile

+CC = gcc
+CFLAGS = -std=gnu99 -Wall -g #-DDEBUG
+LFLAGS = -lpthread -lm
+
+EXECS = pthread_hello time_demo mergesort
+
+all: EXECS
+
+heap-test: heap-test.c
+	$(CC) $(CFLAGS) -o $@ $< 
+
+pipe-test: pipe-test.c
+	$(CC) $(CFLAGS) -o $@ $< 
+.PHONY: clean
+clean:
+	/bin/rm -f *.o $(EXECS)
+

Labs/Lab2/Makefile~

+CC = gcc
+CFLAGS = -std=gnu99 -Wall -g #-DDEBUG
+LFLAGS = -lpthread -lm
+
+EXECS = pthread_hello time_demo mergesort
+
+all: EXECS
+
+pthread_hello: pthread_hello.c
+	$(CC) $(CFLAGS) -o $@ $< $(LFLAGS) 
+
+fork: fork.c
+	$(CC) $(CFLAGS) -o $@ $< 
+
+time_demo: time_demo.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+mergesort: parallelMergesort.c
+	$(CC) $(CFLAGS) -o $@ $< $(LFLAGS)
+
+func_dice_test: func_dice_test.c functional_dice.h
+	$(CC) $(CFLAGS) -o $@ func_dice_test.c
+
+impe_dice_test: impe_dice_test.c imperative_dice.h
+	$(CC) $(CFLAGS) -o $@ impe_dice_test.c
+
+
+.PHONY: clean
+clean:
+	/bin/rm -f *.o $(EXECS)
+

Labs/Lab2/answers-prelab.txt

+1) The parent and children do not share the heap, and that's why the child can not read
+what the parent wrote.
+2)It is because the child inherits open files from parent, and pipe is also 
+an open file.
+3)To create a pipe requires a fd array which is used to return two file descriptors referring
+to the ends of the pipe.To create a file, you need to have a path as input. Also, files have one fd while pipe as an array of 2 fds . pipefd[1] refers 
+to the write end and pipefd[0] is the read end. For file, you also have read and write,
+but you do them with read() and write() functions 

Labs/Lab2/heap-test.c

+#include <stdio.h>
+#include <stdlib.h>
+int main(int argc, char* argv[]){
+  //allocate some space on the heap, data type:int
+  int *pointer;
+  pointer = malloc(sizeof(int));
+  *pointer = 0;
+  int pid;
+  pid = fork();
+  if (0 == pid){
+    int *num1 = *pointer;
+    printf("child reads: %d\n", num1);
+    exit(0);
+  }
+  else{
+    *pointer = 100;
+    int *num2 = *pointer;
+    printf("parent reads: %d\n", num2);
+    exit(0);
+  }
+}

Labs/Lab2/pipe-test.c

+#include <sys/types.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define BUFFER_SIZE 25
+#define READ_END 0
+#define WRITE_END 1
+
+int main(void){
+  char write_msg[BUFFER_SIZE]="Greetings";
+  char read_msg[BUFFER_SIZE];
+  int fd[2];
+  pid_t pid;
+  //create the pipe
+  if (pipe(fd) == 1){
+    fprintf(stderr,"Pipe failed");
+    return 1;
+  }
+  
+  //fork a child process
+  pid = fork();
+  
+  if (pid<0){ //error occurded
+    fprintf(stderr, "Fork Failed");
+    return 1;
+  }
+  
+  if (pid>0){
+    //close the unused end of the pipe
+    close(fd[READ_END]);
+    
+    //write to pipe
+    write(fd[READ_END], write_msg, strlen(write_msg)+1) ;
+   
+    //close the read end of the pipe
+    close(fd[WRITE_END]);
+  }
+  else{
+    //close the unused end of the pipe
+    close(fd[WRITE_END]);
+    
+    //read from the pipe
+    read(fd[READ_END],read_msg, BUFFER_SIZE);
+    printf("read %s", read_msg);
+   
+    //close the write end of the pipe
+    close(fd[READ_END]);
+  }
+  return 0;
+}