Sean Flannigan - Processes

README.md

@@ -1,3 +1,4 @@
+<!-- https://github.com/LambdaSchool/Processes/pull/379 -->
 # Processes and System Calls
 
 Now that we've talked a bit about how processes and system calls work at a high level, it's time to apply these concepts by doing some exercises related to process creation and making system calls. We'll be utilizing the `fork()`, `exec()`, `wait()`, and `pipe()` system calls in order to create processes and even have them pass messages to each other.

ex1/ex1.c

@@ -9,6 +9,19 @@
 int main(void)
 {
     // Your code here
-
+    int x = 100;
+    int rc = fork();
+    // if fork fails return value is -1
+    if(rc < 0){
+        // 'fprintf' is like 'printf' except you add (where, how, what)
+        fprintf(stderr, "failing forks\n");
+        exit(1);
+    } else if (rc == 0) {
+        // successful child fork will return a 0, so this would select the child process
+        printf("This is a child pid: %d\n", (int) getpid());
+    } else {
+        printf("This is the parent pid: %d parent to child pid: %d\n", (int) getpid(), rc);
+    }
+    // printf("%d", x);
     return 0;
 }

ex2/ex2.c

@@ -9,6 +9,29 @@
 int main(void)
 {
     // Your code here 
-
+    FILE *ptr_file;
+    char buf[1000];
+    int rc = fork();
+
+    ptr_file = fopen("./text.txt", "r+");
+    if(!ptr_file) {
+        return 1;
+    }
+
+    while (fgets(buf,1000, ptr_file) != NULL)
+        if(rc < 0) {
+            fprintf(stderr, "unable to fork\n");
+            exit(1);
+        } else if (rc == 0) { // this is the child fork
+            fputs("This has been added from the child process\n", ptr_file);   
+            printf("This is from the child: %s\n", buf);
+
+        } else { // this is the parent
+            fputs("This has been added from the parent process\n", ptr_file);
+            printf("This is from the Parent: %s\n", buf);    
+        }
+
+    fclose(ptr_file);
+
     return 0;
 }

ex2/text.txt

@@ -0,0 +1,2 @@
+this is the text fileThis has been added from the parent process
+This has been added from the child process

ex3/ex3.c

@@ -10,6 +10,16 @@
 int main(void)
 {
     // Your code here
+    int rc = fork();
+
+    if (rc < 0) {
+        fprintf(stderr, "failing forking\n");
+    } else if (rc == 0) {
+        printf("hello\n");
+    } else {
+        int wc = waitpid(rc, NULL, 0);
+        printf("goodbye\n");
+    }
 
     return 0;
 }

ex4/ex4.c

@@ -10,7 +10,16 @@
 
 int main(void)
 {
-    // Your code here    
+    // Your code here
+    int rc = fork();
+    if (rc < 0) {
+        fprintf(stderr, "forking fail\n");
+        exit(1);
+    } else if (rc == 0) {
+        // child
+    } else {
+        // parent
+    }
 
     return 0;
 }

ex5/ex5.c

@@ -17,6 +17,15 @@ char* msg3 = "hello world #3";
 int main(void)
 {
     // Your code here
-
+    int rc = fork();
+
+    if (rc < 0) {
+        fprintf(stderr, "fail fail fail\n");
+        exit(1);
+    } else if (rc == 0) {
+        // this is the child
+    } else {
+        // this is the parent
+    }
     return 0;
 }