Use a more secure command line building method

Previously, a command is built by string concatenation. Here, the
distinction between a value and multiple params got lost. Solve this
by using an array for shell arguments. As the escaping is now removed
from the `rrd_gen_graph` function, the canvas style needs to manually
add those quotes to make the JS code still work. That only supports
double-quotes, so hopefully nobody creates a name with a double quote
as that would break the fragile JS command line parser.

Separate the rrdtool options from the rrdtool graph command to make the
`$graph_type == 'canvas'` option work (it would otherwise not understand
the `rrdtool graph - -a PNG` option).

Merge the SVG and PNG cases as they are the same except for the
Content-Type header.

Fix a missing html escape in a debug style.

1 files changed, 1 insertions, 1 deletions

diff --git a/plugin/cpu.json b/plugin/cpu.json
index 50254f8..34e021d 100644
--- a/plugin/cpu.json
+++ b/plugin/cpu.json
@@ -2,7 +2,7 @@
         "cpu": {
                 "title": "CPU-{{PI}} usage",
                 "vertical": "Jiffies",
-                "rrdtool_opts": "-u 100",
+                "rrdtool_opts": ["-u", "100"],
                 "type": "stacked",
                 "legend": {
                         "idle": {