ash: optional support for $TMOUT variable

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

1 files changed, 47 insertions, 0 deletions

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);