[check-log] Add description for using globs
@@ -11,6 +11,19 @@ Checks a log file using a regular expression.
command = "/path/to/check-log --file=/path/to/file --pattern=REGEXP --warning-over=N --critical-over=N"
```
+### Using glob
+
+You can check multiple files by using globs (and zsh extented globs by [mattn/go-zglob](github.com/mattn/go-zglob)) in `--file` option.
+For example, `--file=/tmp/some.log_*` will check all of `/tmp/some.log_1`, `/tmp/some.log_2`, and so on.
+
+And since `command` in mackerel-agent.conf will be parsed by shell (in *nix `/bin/sh -c`, in Windows `cmd -c`),
+specifying glob like `--file /tmp/some.log_*` does not work as expected.
+It will be expanded like `--file /tmp/some.log_1 /tmp/some.log_2`, so it will check only `/tmp/some.log_1`.
+
+Therefore, when you want to check multiple files, use `--file=<glob>`, not `--file <glob>`.
+
+### Encoding
+
To specify encoding of the log files, you can use `--encoding` option. Below's list of supported encodings.
* UTF-8
