CLI

Every command exits non-zero when the work it names did not succeed, so a build script can rely on the exit code rather than parsing output.

Command	Does
fang init	Create a .copperhead/ workspace
fang build	Elaborate, pass the gate, persist, run the tool plan
fang check	Run the constraint, topology and compatibility checks
fang netlist	Print the compiled components and nets
fang export	Write a KiCad netlist
fang view	Compile a view; render it to SVG with -o
fang sim	Compile a simulation plan, lower it, run it
fang graph	Summarize the kernel graph
fang diff	Diff a program against the persisted workspace

Options

Every command that reads a program takes the same four:

Option	Default	Does
program	required	The Fang program to elaborate
--system	first found	Which system, when a file defines several
--project	PRJ-LOCAL	The project identifier
-C, --directory	.	The project directory

--project is the namespace identifiers are derived in, so changing it changes every identifier in the design. It is not a label.

fang init takes only -C. fang --version reports the version.

Exit codes

Code	Means
0	The work succeeded
1	The work failed: a rejected gate, a failed check or a missing model
2	Usage error

A rejected commit is exit 1, and the diagnostics that explain it go to output. The rejection is the answer, not a crash.

Views

fang view --list
fang view board.py ground -o ground.svg

The six views are system, interconnect, power, ground, interfaces and safety. interconnect is the default when none is named.

Each answers one engineering question and is generated only from facts in the graph. Each also reports its own incompleteness rather than hiding it: a node carrying unknown parameters is drawn with a dashed border.

Simulation

fang sim board.py --analysis transient --stop 10ms --step 1us --probe "V(1)"
fang sim board.py -o deck.cir

Option	Default
--analysis	op (or transient)
--backend	ngspice
--stop	1ms
--step	1us
--probe	none; repeatable
-o, --output	write the SPICE deck here

If a selected component has no compatible model and is not explicitly abstracted, the plan is rejected with the reason rather than run with a substitute. If ngspice is not installed, the plan still compiles and the command says no run was made.