Improve README; check-file-size
Check file size in specified directory.
-## Setting
+## Synopsis
+```
+check-file-size -b /fluentd/buffer_dir/ -w 5M -c 10M
+```
+
+## Installation
+
+First, build this program.
+
+```
+go get github.com/mackerelio/go-check-plugins
+cd $(go env GOPATH)/src/github.com/mackerelio/go-check-plugins/check-file-size
+go install
+```
+
+Or you can use this program by installing the official Mackerel package. See [Using the official check plugin pack for check monitoring - Mackerel Docs](https://mackerel.io/docs/entry/howto/mackerel-check-plugins).
+
+
+Next, you can execute this program :-)
```
-[plugin.checks.filesize]
-command = "/path/to/check-file-size -b /fluentd/buffer_dir/ -w 5M -c 10M"
+check-file-size -b /fluentd/buffer_dir/ -w 5M -c 10M
```
-## Options
+
+## Setting for mackerel-agent
+
+If there are no problems in the execution result, add s setting in mackerel-agent.conf .
```
--b --base The base directory(required)
--w --warning The warning threshold of file size (default: 1K)
--c --critical The critical threshold of file size (default: 1K)
--d --depth Max depth of the directory from base directory (default: 1)
+[plugin.checks.filesize-sample]
+command = ["check-file-size", "-b", "/fluentd/buffer_dir/", "-w", "5M", "-c", "10M"]
```
+
+## Usage
+### Options
+
+```
+ -b, --base= base directory
+ -w, --warning= warning if the size is over (default: 1K)
+ -c, --critical= critical if the size is over (default: 1K)
+ -d, --depth= max depth of the directory from base directory (default: 1)
+```
+
+## For more information
+
+Please execute `check-file-size -h` and you can get command line options.
