From 60c6daacd2d173bcfaa45150bdca1556cde35574 Mon Sep 17 00:00:00 2001
From: Olivier Poitrey <rs@rhapsodyk.net>
Date: Thu, 8 Mar 2018 21:36:47 -0800
Subject: [PATCH] Improve cli help

---
 README.md |  2 +-
 main.go   | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 856c8ef..fc0daed 100644
--- a/README.md
+++ b/README.md
@@ -101,7 +101,7 @@ jplot --url http://:8080/debug/vars \
 
 ### Vegeta
 
-With the help of [jaggr](https://github.com/rs/jaggr] can be used to integrate [vegeta](https://github.com/tsenart/vegeta) with jplot as follow:
+With the help of [jaggr](https://github.com/rs/jaggr) can be used to integrate [vegeta](https://github.com/tsenart/vegeta) with jplot as follow:
 
 ```
 echo 'GET http://localhost:8080' | \
diff --git a/main.go b/main.go
index f50359a..adc4826 100644
--- a/main.go
+++ b/main.go
@@ -16,6 +16,20 @@ import (
 )
 
 func main() {
+	flag.Usage = func() {
+		out := flag.CommandLine.Output()
+		fmt.Fprintln(out, "Usage: jplot [OPTIONS] FIELD_SPEC [FIELD_SPEC...]:")
+		fmt.Fprintln(out, "")
+		fmt.Fprintln(out, "OPTIONS:")
+		flag.PrintDefaults()
+		fmt.Fprintln(out, "")
+		fmt.Fprintln(out, "FIELD_SPEC: [<option>[,<option>...]:]path")
+		fmt.Fprintln(out, "  option:")
+		fmt.Fprintln(out, "    - counter: Computes the difference with the last value. The value must increase monotonically.")
+		fmt.Fprintln(out, "    - marker: When the value is none-zero, a vertical line is drawn.")
+		fmt.Fprintln(out, "  path:")
+		fmt.Fprintln(out, "    JSON field path (eg: field.sub-field).")
+	}
 	url := flag.String("url", "", "URL to fetch every second. Read JSON objects from stdin if not specified.")
 	interval := flag.Duration("interval", time.Second, "When url is provided, defines the interval between fetches."+
 		" Note that counter fields are computed based on this interval.")