initial push of CPU API code

cpu-api/Makefile

@@ -0,0 +1,18 @@
+
+all: p1 p2 p3 p4
+
+clean:
+	rm -f p1 p2 p3 p4
+
+p1: p1.c
+	gcc -o p1 p1.c -Wall
+
+p2: p2.c
+	gcc -o p2 p2.c -Wall
+
+p3: p3.c
+	gcc -o p3 p3.c -Wall
+
+p4: p4.c
+	gcc -o p4 p4.c -Wall
+

cpu-api/README.md

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+
+To compile, just type "make".
+
+See the highly primitive "Makefile" for details.
+
+Then run p1, p2, p3, or p4, as need be.
+
+

cpu-api/p1.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int
+main(int argc, char *argv[])
+{
+    printf("hello world (pid:%d)\n", (int) getpid());
+    int rc = fork();
+    if (rc < 0) {
+        // fork failed; exit
+        fprintf(stderr, "fork failed\n");
+        exit(1);
+    } else if (rc == 0) {
+        // child (new process)
+        printf("hello, I am child (pid:%d)\n", (int) getpid());
+    } else {
+        // parent goes down this path (original process)
+        printf("hello, I am parent of %d (pid:%d)\n",
+	       rc, (int) getpid());
+    }
+    return 0;
+}

cpu-api/p2.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+int
+main(int argc, char *argv[])
+{
+    printf("hello world (pid:%d)\n", (int) getpid());
+    int rc = fork();
+    if (rc < 0) {
+        // fork failed; exit
+        fprintf(stderr, "fork failed\n");
+        exit(1);
+    } else if (rc == 0) {
+        // child (new process)
+        printf("hello, I am child (pid:%d)\n", (int) getpid());
+	sleep(1);
+    } else {
+        // parent goes down this path (original process)
+        int wc = wait(NULL);
+        printf("hello, I am parent of %d (wc:%d) (pid:%d)\n",
+	       rc, wc, (int) getpid());
+    }
+    return 0;
+}

cpu-api/p3.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/wait.h>
+
+int
+main(int argc, char *argv[])
+{
+    printf("hello world (pid:%d)\n", (int) getpid());
+    int rc = fork();
+    if (rc < 0) {
+        // fork failed; exit
+        fprintf(stderr, "fork failed\n");
+        exit(1);
+    } else if (rc == 0) {
+        // child (new process)
+        printf("hello, I am child (pid:%d)\n", (int) getpid());
+        char *myargs[3];
+        myargs[0] = strdup("wc");   // program: "wc" (word count)
+        myargs[1] = strdup("p3.c"); // argument: file to count
+        myargs[2] = NULL;           // marks end of array
+        execvp(myargs[0], myargs);  // runs word count
+        printf("this shouldn't print out");
+    } else {
+        // parent goes down this path (original process)
+        int wc = wait(NULL);
+        printf("hello, I am parent of %d (wc:%d) (pid:%d)\n",
+	       rc, wc, (int) getpid());
+    }
+    return 0;
+}

cpu-api/p4.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <sys/wait.h>
+
+int
+main(int argc, char *argv[])
+{
+    int rc = fork();
+    if (rc < 0) {
+        // fork failed; exit
+        fprintf(stderr, "fork failed\n");
+        exit(1);
+    } else if (rc == 0) {
+	// child: redirect standard output to a file
+	close(STDOUT_FILENO); 
+	open("./p4.output", O_CREAT|O_WRONLY|O_TRUNC, S_IRWXU);
+
+	// now exec "wc"...
+        char *myargs[3];
+        myargs[0] = strdup("wc");   // program: "wc" (word count)
+        myargs[1] = strdup("p4.c"); // argument: file to count
+        myargs[2] = NULL;           // marks end of array
+        execvp(myargs[0], myargs);  // runs word count
+    } else {
+        // parent goes down this path (original process)
+        int wc = wait(NULL);
+	assert(wc >= 0);
+    }
+    return 0;
+}