child runs wc
$ cat -n ostep/code/cpu-api/p3.c
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <unistd.h>
4 #include <string.h>
5 #include <sys/wait.h>
6
7 int
8 main(int argc, char *argv[])
9 {
10 printf("hello world (pid:%d)\n", (int) getpid());
11 int rc = fork();
12 if (rc < 0) {
13 // fork failed; exit
14 fprintf(stderr, "fork failed\n");
15 exit(1);
16 } else if (rc == 0) {
17 // child (new process)
18 printf("hello, I am child (pid:%d)\n", (int) getpid());
19 char *myargs[3];
20 myargs[0] = strdup("wc"); // program: "wc" (word count)
21 myargs[1] = strdup("p3.c"); // argument: file to count
22 myargs[2] = NULL; // marks end of array
23 execvp(myargs[0], myargs); // runs word count
24 printf("this shouldn't print out");
25 } else {
26 // parent goes down this path (original process)
27 int wc = wait(NULL);
28 printf("hello, I am parent of %d (wc:%d) (pid:%d)\n",
29 rc, wc, (int) getpid());
30 }
31 return 0;
32 }
$ ./p3
hello world (pid:22206)
hello, I am child (pid:22207)
32 123 966 p3.c
hello, I am parent of 22207 (wc:22207) (pid:22206)
$
