[spp] [PATCH 3/5] docs: add launch command in primary

[ogawa.yasufumi@lab.ntt.co.jp]

From: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>

This update is to add launch sub command of primary to `Commands`
section.

Signed-off-by: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
---
 docs/guides/commands/primary.rst | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/docs/guides/commands/primary.rst b/docs/guides/commands/primary.rst
index 11e378c..5032b37 100644
--- a/docs/guides/commands/primary.rst
+++ b/docs/guides/commands/primary.rst
@@ -35,3 +35,39 @@ Clear statistics.
 .. code-block:: console
 
     spp > pri; clear
+
+
+launch
+------
+
+Launch secondary process.
+
+Spp_primary is able to launch a secondary process with given type, secondary
+ID and options of EAL and application itself. This is a list of supported type
+of secondary processes.
+
+  * nfv
+  * vf
+  * mirror
+  * pcap
+
+.. code-block:: console
+
+    # spp_nfv with sec ID 1
+    spp > pri; launch nfv 1 -l 1,2 -m 512 -- -n -s 192.168.1.100:6666
+
+    # spp_vf with sec ID 2
+    spp > pri; launch vf 2 -l 1,3-5 -m 512 -- --client-id -s 192.168.1.100:6666
+
+You notice that ``--proc-type secondary`` is not given for launching secondary
+processes. ``launch`` command adds this option before requesting to launch
+the process so that you do not need to input this option by yourself.
+
+``launch`` command supports TAB completion for type, secondary ID and the rest
+of options. Some of EAL and application options are just a template, so you
+should update them before launching.
+
+In terms of log, each of secondary processes are output its log messages to
+files under ``log`` directory of project root. The name of log file is defined
+with type of process and secondary ID. For instance, ``nfv 2``, the path of log
+file is ``log/spp_nfv-2.log``.
-- 
2.7.4