cmd Transform
Execute an external command and capture its stdout. Use this to integrate with tools like jsonnet, jq, yq, or any custom processor.
Usage
node:
template:
from_file: config.jsonnet
config:
to_file: config.json
transform:
cmd:
- jsonnet
- "{{.meta.template.path}}"
Behavior
- The command is executed with the specified arguments
- stdout is captured and parsed as YAML/JSON
- The parsed data is then encoded to the output file format
- stderr is captured and shown in error messages
- Non-zero exit codes cause the transform to fail
Note: Command output must be valid YAML or JSON. This allows panconf to:
- Re-encode the output to different formats (JSON, YAML, TOML)
- Use the output as input for other nodes via
{{.nodeName}}
Examples
Jsonnet
template.jsonnet:
{
name: "app",
port: 8080,
replicas: std.parseInt(std.extVar("REPLICAS")),
}
panconf.yaml:
node:
template:
from_file: template.jsonnet
config:
to_file: config.json
transform:
cmd:
- jsonnet
- "{{.meta.template.path}}"
jq Processing
node:
input:
from_file: data.json
filtered:
to_file: filtered.json
transform:
cmd:
- jq
- ".items | map(select(.active))"
- "{{.meta.input.path}}"
yq for YAML
node:
input:
from_file: data.yaml
output:
to_file: output.yaml
transform:
cmd:
- yq
- ".metadata.name = \"new-name\""
- "{{.meta.input.path}}"
cat (Simple Pass-through)
transform:
cmd:
- cat
- "{{.meta.source.path}}"
Shell Script
transform:
cmd:
- bash
- "-c"
- "cat {{.meta.base.path}} {{.meta.override.path}} | jq -s '.[0] * .[1]'"
Multiple Input Files
You can reference multiple inputs:
node:
base:
from_file: base.json
overlay:
from_file: overlay.json
merged:
to_file: merged.json
transform:
cmd:
- jq
- "-s"
- ".[0] * .[1]"
- "{{.meta.base.path}}"
- "{{.meta.overlay.path}}"
With Environment Variables
Environment variables are expanded in the panconf config, and also available to the command:
node:
template:
from_file: template.jsonnet
config:
to_file: config.json
transform:
cmd:
- bash
- "-c"
- "jsonnet --ext-str env=$ENVIRONMENT {{.meta.template.path}}"
Error Handling
When a command fails:
command failed: exit status 1
stderr: jq: error: syntax error, unexpected IDENT, expecting $end
The error includes:
