ash: optional support for $TMOUT variable

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 50 insertions, 1 deletions

diff --git a/include/libbb.h b/include/libbb.h
index a0e23697c..6358e654a 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1393,12 +1393,14 @@ enum {
 };
 line_input_t *new_line_input_t(int flags) FAST_FUNC;
 /* So far static: void free_line_input_t(line_input_t *n) FAST_FUNC; */
-/* maxsize must be >= 2.
+/*
+ * maxsize must be >= 2.
  * Returns:
  * -1 on read errors or EOF, or on bare Ctrl-D,
  * 0  on ctrl-C (the line entered is still returned in 'command'),
  * >0 length of input string, including terminating '\n'
  */
+/* NB: ash has timeout code which can be moved into read_line_input, if needed */
 int read_line_input(const char* prompt, char* command, int maxsize, line_input_t *state) FAST_FUNC;
 #else
 #define MAX_HISTORY 0
diff --git a/shell/ash.c b/shell/ash.c
index 0e27a073c..bdc64790c 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -97,6 +97,14 @@
 //config:	help
 //config:	  Enable bash-compatible extensions.
 //config:
+//config:config ASH_IDLE_TIMEOUT
+//config:	bool "Idle timeout variable"
+//config:	default n
+//config:	depends on ASH
+//config:	help
+//config:	  Enables bash-like auto-logout after "$TMOUT" seconds
+//config:	  of idle time.
+//config:
 //config:config ASH_JOB_CONTROL
 //config:	bool "Job control"
 //config:	default y
@@ -12048,6 +12056,23 @@ evalcmd(int argc UNUSED_PARAM, char **argv)
 	return exitstatus;
 }
 
+#if ENABLE_ASH_IDLE_TIMEOUT
+static smallint timed_out;
+
+static void alrm_sighandler(int sig UNUSED_PARAM)
+{
+	/* Close stdin, making interactive command reading stop.
+	 * Otherwise, timeout doesn't trigger until <Enter> is pressed.
+	 */
+	int sv = errno;
+	close(0);
+	open("/dev/null", O_RDONLY);
+	errno = sv;
+
+	timed_out = 1;
+}
+#endif
+
 /*
  * Read and execute commands.
  * "Top" is nonzero for the top level command loop;
@@ -12064,6 +12089,20 @@ cmdloop(int top)
 	TRACE(("cmdloop(%d) called\n", top));
 	for (;;) {
 		int skip;
+#if ENABLE_ASH_IDLE_TIMEOUT
+		int tmout_seconds = 0;
+
+		if (top && iflag) {
+			const char *tmout_var = lookupvar("TMOUT");
+			if (tmout_var) {
+				tmout_seconds = atoi(tmout_var);
+				if (tmout_seconds > 0) {
+					signal(SIGALRM, alrm_sighandler);
+					alarm(tmout_seconds);
+				}
+			}
+		}
+#endif
 
 		setstackmark(&smark);
 #if JOBS
@@ -12076,6 +12115,14 @@ cmdloop(int top)
 			chkmail();
 		}
 		n = parsecmd(inter);
+#if ENABLE_ASH_IDLE_TIMEOUT
+		if (timed_out) {
+			printf("\007timed out waiting for input: auto-logout\n");
+			break;
+		}
+		if (tmout_seconds > 0)
+			alarm(0);
+#endif
 #if DEBUG
 		if (DEBUG > 2 && debug && (n != NODE_EOF))
 			showtree(n);