Add --reverse flag to wait until the port is no longer available

README.md

@@ -9,6 +9,8 @@ wait-for-it.sh host:port [-s] [-t timeout] [-- command args]
 -h HOST | --host=HOST       Host or IP under test
 -p PORT | --port=PORT       TCP port under test
                             Alternatively, you specify the host and port as host:port
+-r | --reverse              Perform the reverse test, wait until a port is
+                            no longer available
 -s | --strict               Only execute subcommand if the test succeeds
 -q | --quiet                Don't output any status messages
 -t TIMEOUT | --timeout=TIMEOUT
@@ -36,6 +38,15 @@ wait-for-it.sh: www.google.com:80 is available after 0 seconds
 google is up
 ```
 
+You can perform the reverse test with the `-r` or `--reverse` option.  Setting the reverse flag will check if the port is unavailable and if it is, echo the message `port is unavailable`.
+
+```
+$ ./wait-for-it.sh localhost:0 --reverse -- echo "port is unavailable"
+wait-for-it.sh: waiting 15 seconds for localhost:0
+wait-for-it.sh: localhost:0 is unavailable after 0 seconds
+port is unavailable
+```
+
 The subcommand will be executed regardless if the service is up or not.  If you wish to execute the subcommand only if the service is up, add the `--strict` argument. In this example, we will test port 81 on www.google.com which will fail:
 
 ```

test/wait-for-it.py

@@ -113,6 +113,17 @@ def test_host_port(self):
         )
         soc.close()
 
+    def test_reverse_host_port(self):
+        """ Check that --reverse args work correctly """
+        soc, port = self.open_local_port()
+        soc.close()
+        self.check_args(
+            "--host=localhost --port={0} --timeout=1 --reverse".format(port),
+            "",
+            ".*wait-for-it.sh: localhost:{0} is unavailable after 0 seconds".format(port),
+            True
+        )
+
     def test_combined_host_port(self):
         """
             Tests that wait-for-it.sh returns correctly after establishing a
@@ -130,7 +141,7 @@ def test_combined_host_port(self):
 
     def test_port_failure_with_timeout(self):
         """
-            Note exit status of 124 is exected, passed from the timeout command
+            Note exit status of 124 is expected, passed from the timeout command
         """
         self.check_args(
             "localhost:8929 --timeout=1",

wait-for-it.sh

@@ -9,10 +9,12 @@ usage()
 {
     cat << USAGE >&2
 Usage:
-    $WAITFORIT_cmdname host:port [-s] [-t timeout] [-- command args]
+    $WAITFORIT_cmdname host:port [-r] [-s] [-t timeout] [-- command args]
     -h HOST | --host=HOST       Host or IP under test
     -p PORT | --port=PORT       TCP port under test
                                 Alternatively, you specify the host and port as host:port
+    -r | --reverse              Perform the reverse test, wait until a port is
+                                no longer available
     -s | --strict               Only execute subcommand if the test succeeds
     -q | --quiet                Don't output any status messages
     -t TIMEOUT | --timeout=TIMEOUT
@@ -32,31 +34,32 @@ wait_for()
     WAITFORIT_start_ts=$(date +%s)
     while :
     do
+        WAITFORIT_test_success=$([[ $WAITFORIT_REVERSE -eq 0 ]] && echo 0 || echo 1)
         if [[ $WAITFORIT_ISBUSY -eq 1 ]]; then
             nc -z $WAITFORIT_HOST $WAITFORIT_PORT
             WAITFORIT_result=$?
         else
             (echo > /dev/tcp/$WAITFORIT_HOST/$WAITFORIT_PORT) >/dev/null 2>&1
             WAITFORIT_result=$?
         fi
-        if [[ $WAITFORIT_result -eq 0 ]]; then
+        if [[ $WAITFORIT_result -eq $WAITFORIT_test_success ]]; then
             WAITFORIT_end_ts=$(date +%s)
-            echoerr "$WAITFORIT_cmdname: $WAITFORIT_HOST:$WAITFORIT_PORT is available after $((WAITFORIT_end_ts - WAITFORIT_start_ts)) seconds"
+            WAITFORIT_availability=$([[ $WAITFORIT_REVERSE -eq 0 ]] && echo "available" || echo "unavailable")
+            echoerr "$WAITFORIT_cmdname: $WAITFORIT_HOST:$WAITFORIT_PORT is $WAITFORIT_availability after $((WAITFORIT_end_ts - WAITFORIT_start_ts)) seconds"
             break
         fi
         sleep 1
     done
-    return $WAITFORIT_result
+    return $([[ $WAITFORIT_result -eq $WAITFORIT_test_success ]] && echo 0 || echo 1)
 }
 
 wait_for_wrapper()
 {
+    WAITFORIT_QUIETFLAG=$([[ $WAITFORIT_QUIET -eq 1 ]] && echo "--quiet")
+    WAITFORIT_REVERSEFLAG=$([[ $WAITFORIT_REVERSE -eq 1 ]] && echo "--reverse")
+
     # In order to support SIGINT during timeout: http://unix.stackexchange.com/a/57692
-    if [[ $WAITFORIT_QUIET -eq 1 ]]; then
-        timeout $WAITFORIT_BUSYTIMEFLAG $WAITFORIT_TIMEOUT $0 --quiet --child --host=$WAITFORIT_HOST --port=$WAITFORIT_PORT --timeout=$WAITFORIT_TIMEOUT &
-    else
-        timeout $WAITFORIT_BUSYTIMEFLAG $WAITFORIT_TIMEOUT $0 --child --host=$WAITFORIT_HOST --port=$WAITFORIT_PORT --timeout=$WAITFORIT_TIMEOUT &
-    fi
+    timeout $WAITFORIT_BUSYTIMEFLAG $WAITFORIT_TIMEOUT $0 --child --host=$WAITFORIT_HOST --port=$WAITFORIT_PORT $WAITFORIT_REVERSEFLAG $WAITFORIT_REVERSEFLAG --timeout=$WAITFORIT_TIMEOUT &
     WAITFORIT_PID=$!
     trap "kill -INT -$WAITFORIT_PID" INT
     wait $WAITFORIT_PID
@@ -85,6 +88,10 @@ do
         WAITFORIT_QUIET=1
         shift 1
         ;;
+        -r | --reverse)
+        WAITFORIT_REVERSE=1
+        shift 1
+        ;;
         -s | --strict)
         WAITFORIT_STRICT=1
         shift 1
@@ -137,9 +144,10 @@ if [[ "$WAITFORIT_HOST" == "" || "$WAITFORIT_PORT" == "" ]]; then
 fi
 
 WAITFORIT_TIMEOUT=${WAITFORIT_TIMEOUT:-15}
-WAITFORIT_STRICT=${WAITFORIT_STRICT:-0}
 WAITFORIT_CHILD=${WAITFORIT_CHILD:-0}
 WAITFORIT_QUIET=${WAITFORIT_QUIET:-0}
+WAITFORIT_REVERSE=${WAITFORIT_REVERSE:-0}
+WAITFORIT_STRICT=${WAITFORIT_STRICT:-0}
 
 # Check to see if timeout is from busybox?
 WAITFORIT_TIMEOUT_PATH=$(type -p timeout)