initial import

from
http://www.informit.com/store/programming-with-posix-threads-9780201633924

alarm_fork.c

@@ -0,0 +1,56 @@
+/*
+ * alarm_fork.c
+ *
+ * This version of alarm.c uses fork to create a new process to
+ * wait for each alarm to expire.
+ */
+#include <sys/types.h>
+#include <wait.h>
+#include "errors.h"
+
+int main (int argc, char *argv[])
+{
+    int status;
+    char line[128];
+    int seconds;
+    pid_t pid;
+    char message[64];
+
+    while (1) {
+        printf ("Alarm> ");
+        if (fgets (line, sizeof (line), stdin) == NULL) exit (0);
+        if (strlen (line) <= 1) continue;
+
+        /*
+         * Parse input line into seconds (%d) and a message
+         * (%64[^\n]), consisting of up to 64 characters
+         * separated from the seconds by whitespace.
+         */
+        if (sscanf (line, "%d %64[^\n]", 
+            &seconds, message) < 2) {
+            fprintf (stderr, "Bad command\n");
+        } else {
+            pid = fork ();
+            if (pid == (pid_t)-1)
+                errno_abort ("Fork");
+            if (pid == (pid_t)0) {
+                /*
+                 * If we're in the child, wait and then print a message
+                 */
+                sleep (seconds);
+                printf ("(%d) %s\n", seconds, message);
+                exit (0);
+            } else {
+                /*
+                 * In the parent, call waitpid() to collect any children that
+                 * have already terminated.
+                 */
+                do {
+                    pid = waitpid ((pid_t)-1, NULL, WNOHANG);
+                    if (pid == (pid_t)-1)
+                        errno_abort ("Wait for child");
+                } while (pid != (pid_t)0);
+            }
+        }
+    }
+}