+ *
+ * Example:
+ * // Run 1000 of the given commandline at best-known parallel rate.
+ * // See tools/lbalance.c for a sligtly more serious example.
+ * #include <ccan/lbalance/lbalance.h>
+ * #include <sys/types.h>
+ * #include <sys/time.h>
+ * #include <sys/resource.h>
+ * #include <sys/wait.h>
+ * #include <err.h>
+ *
+ * #define MAX 1000
+ *
+ * static pid_t spawn(char *args[])
+ * {
+ * pid_t pid = fork();
+ *
+ * if (pid == -1)
+ * err(1, "forking");
+ * if (pid == 0) {
+ * execvp(args[0], args);
+ * err(1, "exec failed");
+ * }
+ * return pid;
+ * }
+ *
+ * int main(int argc, char *argv[])
+ * {
+ * unsigned int num = 0, num_running = 0;
+ * pid_t pids[MAX];
+ * struct lbalance_task *tasks[MAX];
+ * struct lbalance *lb;
+ *
+ * if (argc == 1)
+ * errx(1, "Usage: %s cmdline...", argv[0]);
+ *
+ * lb = lbalance_new();
+ *
+ * while (num - num_running < MAX) {
+ * struct rusage ru;
+ * pid_t pid;
+ * unsigned int i;
+ *
+ * // Make sure we're running as many as lbalance says to.
+ * while (num_running < lbalance_target(lb) && num < MAX) {
+ * pids[num] = spawn(argv+1);
+ * tasks[num] = lbalance_task_new(lb);
+ * num++;
+ * num_running++;
+ * }
+ *
+ * // Now wait for something to die.
+ * pid = wait3(NULL, 0, &ru);
+ * // Find it, tell lbalance it's finished.
+ * for (i = 0; i < num; i++) {
+ * if (pids[i] == pid) {
+ * lbalance_task_free(tasks[i], &ru);
+ * pids[i] = 0;
+ * break;
+ * }
+ * }
+ * num_running--;
+ * }
+ * lbalance_free(lb);
+ * return 0;
+ * }