1 files changed, 61 insertions, 0 deletions
diff --git a/libc/manual/examples/sigusr.c b/libc/manual/examples/sigusr.c
new file mode 100644
index 000000000..11e3ceee8
--- /dev/null
+++ b/libc/manual/examples/sigusr.c
@@ -0,0 +1,61 @@
+/*@group*/
+#include <signal.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+/*@end group*/
+
+/* When a @code{SIGUSR1} signal arrives, set this variable.  */
+volatile sig_atomic_t usr_interrupt = 0;
+
+void 
+synch_signal (int sig)
+{
+  usr_interrupt = 1;
+}
+
+/* The child process executes this function. */
+void 
+child_function (void)
+{
+  /* Perform initialization. */
+  printf ("I'm here!!!  My pid is %d.\n", (int) getpid ());
+
+  /* Let parent know you're done. */
+  kill (getppid (), SIGUSR1);
+
+  /* Continue with execution. */
+  puts ("Bye, now....");
+  exit (0);
+}
+
+int
+main (void)
+{
+  struct sigaction usr_action;
+  sigset_t block_mask;
+  pid_t child_id;
+
+  /* Establish the signal handler. */
+  sigfillset (&block_mask);
+  usr_action.sa_handler = synch_signal;
+  usr_action.sa_mask = block_mask;
+  usr_action.sa_flags = 0;
+  sigaction (SIGUSR1, &usr_action, NULL);
+
+  /* Create the child process. */
+  child_id = fork ();
+  if (child_id == 0)
+    child_function ();		/* Does not return.  */
+
+/*@group*/
+  /* Busy wait for the child to send a signal. */
+  while (!usr_interrupt)
+    ;
+/*@end group*/
+
+  /* Now continue execution. */
+  puts ("That's all, folks!");
+
+  return 0;
+}