update README

README.md

@@ -9,6 +9,36 @@ Config read order:
 1. from `~/.oss-backupd-config.json`
 1. from `/etc/oss-backupd/config.json`
 
+Usage:
+
+Help
+```
+oss-backupd -h
+Usage:
+  ./target/debug/oss-backupd [OPTIONS]
+
+oss_backupd - command line OSS backup tool.
+
+Optional arguments:
+  -h,--help             Show this help message and exit
+  -V,--version          Print version
+  -v,--verbose          Verbose
+  -c,--config CONFIG    Config file
+```
+
+Run with config file
+```
+oss-backupd -c sample-backupd-config.json
+Compressing opt.rs, Finished: 1.16KB, Speed: -
+Compressing oss_util.rs, Finished: 5.28KB, Speed: -
+Compressing pgp_util.rs, Finished: 3.00KB, Speed: -
+Compressing config_util.rs, Finished: 10.84KB, Speed: -
+Compressing main.rs, Finished: 9.25KB, Speed: -
+Compressing zip_util.rs, Finished: 2.57KB, Speed: -
+[OK   ] Success, at item index: 0
+[OK   ] Backup all file(s) finished!
+```
+
 
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