first commit

examples/ping-and-mail.scm

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+#!/bin/sh
+exec scsh -lel expect/load.scm -o threads -o expect -o let-opt -e main -s "$0" "$@"
+!#
+
+(define *respond-time* 2)
+(define *sendmail* "/usr/sbin/sendmail")
+(define verbose? #t)
+
+(define (display-mail address dead-hosts)
+  (display "From: ping-and-mail\n")
+  (display (format #f "To: ~a\n" address))
+  (display "Subject: Dead hosts detected\n\n")
+  (display "The following hosts did not react to a ping within a ")
+  (display (format #f "period of ~a seconds:" (number->string *respond-time*)))
+  (display "\n")
+  (for-each (lambda (s) (display (format #f "~a\n" s))) dead-hosts)
+  (display ".\n"))
+
+(define (send-mail address dead-hosts)
+  (wait (fork (lambda ()
+		(fork/pipe (lambda ()
+			     ;; child (stdout)
+			     (display-mail address dead-hosts)))
+		;; parent (stdin)
+		(exec-epf (,*sendmail* ,address))))))
+
+(define (dead? host)
+  (let ((task (spawn (ping -c 1 ,host))))
+    (let ((res (chat task
+		     (chat-timeout *respond-time*)
+		     (look-for (rx "1 " (* (- any #\,)) "received") #f)
+		     'alive)))
+      (close-task task)
+      (not (eq? res 'alive)))))
+
+(define (main args)
+  (if (or (< (length args) 2) (string=? (cadr args) "--help"))
+      (display-usage)
+      (let* ((hosts (cddr args))
+	     (address (cadr args))
+	     (dead (filter (lambda (h)
+			     (let ((d (dead? h)))
+			       (if verbose?
+				   (display (format #f "~a: ~a\n"
+						    h (if d "dead" "alive"))))
+			       d))
+			   hosts)))
+	(if (not (null? dead))
+	    (begin
+	      (send-mail address dead)
+	      (if verbose?
+		  (display (format #f "Mail sent to ~a\n" address))))
+	    (if verbose?
+		(display "No hosts dead\n"))))))
+
+(define (display-usage)
+  (display "Usage: ping-and-mail.scm emailaddress host ...\n"))