Processes - Evan Carlstrom

ex1/ex1.c

@@ -9,6 +9,23 @@
 int main(void)
 {
     // Your code here
+    int x = 100;
+    int pid = fork();
+
+    if(pid < 0) {
+        fprintf(stderr, "Fork failed!\n");
+        exit(1);
+    }
+    else if(pid == 0) {
+        printf("Hello, I'm a child process!\n");
+    }
+    else {
+        printf("Hello, I'm a parent process!\n");
+    }
+    printf("%d %d", 100, x);
 
     return 0;
 }
+
+/* After initialization, the variable in the child process would be the same as its value in the parent process. When the parent and child change the value of x, we can access both values of x within their respective forks.
+If we were to do something like (x * 2) in the parent fork and (x / 2) in the child fork, we could work with both 200 and 50. */

ex2/ex2.c

@@ -9,6 +9,25 @@
 int main(void)
 {
     // Your code here 
-
+    FILE * file_pointer;
+
+    file_pointer = fopen("text.txt", "r+");
+    int pid = fork();
+
+    if(pid < 0) {
+        fprintf(stderr, "Fork failed!\n");
+        exit(1);
+    }
+    else if(pid == 0) {
+        fprintf(file_pointer, "%s %s", "Child", "text.\n");
+        fclose(file_pointer);
+    }
+    else {
+        fprintf(file_pointer, "%s %s", "Parent", "text.");
+        fclose(file_pointer);
+    }
+
     return 0;
 }
+
+/* Yes, both child and parent can access the file returned by fopen(). In the case of concurrent attempts, they are saved together as in the example above. */

ex2/text.txt

@@ -0,0 +1 @@
+Parent text.Child text.

ex3/ex3.c

@@ -10,6 +10,23 @@
 int main(void)
 {
     // Your code here
+    pid_t pid = fork();
+    // waitpid(pid, NULL, 0);
+
+    if(pid < 0) {
+        fprintf(stderr, "Fork failed!\n");
+        exit(1);
+    }
+    else if(pid == 0) {
+        printf("%s", "hello\n");
+        // waitpid(pid, NULL, 0);
+    }
+    else {
+        waitpid(pid, NULL, 0);
+        printf("%s", "goodbye\n");    
+    }
 
     return 0;
 }
+
+/* currently testing out the results of implementing waitpid() in various spots in the code */

ex4/ex4.c

@@ -11,6 +11,19 @@
 int main(void)
 {
     // Your code here    
+    pid_t pid = fork();
 
+    char *bin_ref = {"./bin/ls", NULL}; /* might try running another file from this project at some point too */
+    exec(bin_ref[0], bin_ref);
+    // execl(bin_ref[0], bin_ref);
+    // execle(bin_ref[0], bin_ref);
+    // execvp(bin_ref[0], bin_ref);
     return 0;
 }
+
+/* The different versions seem to mainly reference parameters.
+For example, -l includes individual parameters in the call, whereas -v is useful when
+variables are not known in advance because it allows you to pass in a char* array
+rather than a specific number of parameters. There is some additional functionality 
+with things like -e and -p and I'd be lying if I said I understand this fully yet, so
+I'm going to keep looking into these differences. */

ex5/ex5.c

@@ -17,6 +17,33 @@ char* msg3 = "hello world #3";
 int main(void)
 {
     // Your code here
+    char inbuf[MSGSIZE];
+    int p[2];
+
+    if(pipe(p) < 0) {
+        fprintf(stderr, "Pipe failure!\n");
+        exit(1); /* yesterday's error handling example applied to the pipe */
+    }
 
+    pid_t pid = fork();
+
+    if(pid < 0) {
+        fprintf(stderr, "Fork failure!\n");
+        exit(1); /* fork error handling */
+    }
+    else if(pid == 0) {
+        /* write the msg entries to the pipe */
+        write(p[1], msg1, MSGSIZE);
+        write(p[1], msg2, MSGSIZE);
+        write(p[1], msg3, MSGSIZE);
+    }
+    else {
+        for(int i = 0; i < 3; i++) {
+            /* reads the data from the pipe and outputs it */
+            read(p[0], inbuf, MSGSIZE);
+            printf("%s\n", inbuf);
+        }
+    }
+
     return 0;
 }

ex6/ex6.c

@@ -12,6 +12,7 @@ and `clock_gettime()` should work just fine.
 */
 
 #include <stdio.h>
+#include <stdint.h>
 #include <unistd.h>
 #include <time.h>
 
@@ -21,6 +22,21 @@ and `clock_gettime()` should work just fine.
 int main()
 {
     // Your code here
+    uint64_t diff;
+    struct timespec start, end;
+    int i;
+
+    /* basic structure */
+    clock_gettime(CLOCK_MONOTONIC, &start);
+
+    for(i = 0; i < number_iter; i++) {
+        write(fileno(stdout), NULL, 0);
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &end);
+
+    diff = BILLION * (end.tv_sec - start.tv_sec) + end.tv_nsec - start.tv_nsec;
+    printf("Time elapsed: %llu nanoseconds\n", (long long unsigned int) diff);
 
     return 0;
 }

stretch/src/balance.txt

@@ -0,0 +1 @@
+10000

stretch/src/bankers.c

@@ -90,6 +90,15 @@ int get_random_amount(void)
 	// !!!! IMPLEMENT ME:
 
 	// Return a random number between 0 and 999 inclusive using rand()
+	int i, count, lower, upper; /* upper and lower will provide our rand() range */
+	lower = 0;
+	upper = 999;
+	count = 1;
+
+	for(i = 0; i < count; i++){
+		int rng = (rand() % (upper - lower + 1)) + lower;
+		printf("%d ", rng);
+	}
 
 	// ^^^^^^^^^^^^^^^^^^
 }
@@ -116,10 +125,15 @@ int main(int argc, char **argv)
 	// message to stderr, and exit with status 1:
 	//
 	// "usage: bankers numprocesses\n"
-
+	if(argc == 0) {
+		fprintf(stderr, "Usage: bankers numprocesses\n");
+		exit(1);
+	}
 	// Store the number of processes in this variable:
 	// How many processes to fork at once
-	int num_processes = IMPLEMENT ME
+	int num_processes = argc;
+
+	/* learning about getopt() right now to try and parse arguments */
 
 	// Make sure the number of processes the user specified is more than
 	// 0 and print an error to stderr if not, then exit with status 2:
@@ -151,17 +165,29 @@ int main(int argc, char **argv)
 
 			// Open the balance file (feel free to call the helper
 			// functions, above).
+
+			int fp = open_balance_file(BALANCE_FILE);
 
 			// Read the current balance
+			int read = read_balance();
 
 			// Try to withdraw money
-			//
+
+			int withdrawal = get_random_amount();
+
 			// Sample messages to print:
-			//
+			if(withdrawal >= balance) {
+				printf("Withdrew $%d, new balance $%d\n", withdrawal, balance);
+			}
+			else {
+				printf("Only have $%d, can't withdraw $%d\n", balance, withdrawal);
+			}
 			// "Withdrew $%d, new balance $%d\n"
 			// "Only have $%d, can't withdraw $%d\n"
 
 			// Close the balance file
+
+			int fp_close = close_balance_file(BALANCE_FILE);
 			//^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 			// Child process exits