Add usage sample of sftp (#197)

Co-authored-by: I306454 <jiabin.zheng01@sap.com>

command/sftp.md

@@ -30,5 +30,28 @@ sftp(选项)(参数)
 
 目标主机：指定sftp服务器ip地址或者主机名。
 
+###  实例
+
+建立联接
+
+```shell
+$ sfpt username@1.1.1.1 # 回车输入密码
+```
+
+获取文件下载到指定路径
+
+```shell
+sftp> get /export/sftp/test.csv /Users/my/Downloads
+Fetching /export/sftp/test.csv to /Users/my/Downloads/test.csv
+/export/sftp/test.csv            100%  133     0.3KB/s   00:00
+```
+
+上传本地文件到服务器指定路径
+
+```shell
+sftp> put /Users/my/Downloads/re-produce.gif /export/sftp
+Uploading /Users/my/Downloads/re-produce.gif to /export/sftp/re-produce.gif
+/Users/my/Downloads/re-produce.gif            100%  257KB  86.6KB/s   00:02
+```
 
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