Represents a file output sink.
Writes simulation outputs to a CSV file path. Acts as a sink with file output behavior.
This block declares no output ports.
These serialized keys are exposed by the block inspector.
This page describes the native runtime behavior observed in the module C++ sources. Declared phases indicate when the simulation engine calls the block.
Code generation: supported for C and Rust.
Manifestmodules/nflow_blocks/libraries/sink/library.json
{
"id": "builtin.sink",
"title": "Sinks",
"version": "1.0.0",
"format": "nflow-2",
"metadata": {
"author": "Allan CORNET",
"created": "2026-03-21",
"tool": "Nelson nflow"
},
"comment": "Blocks for visualizing or exporting simulation results",
"license": "LGPL-3.0",
"builtin": true,
"blocks": [
{
"type": "scope",
"label": "Scope",
"icon": "scope.svg",
"phases": [
"INIT",
"AFTER_STEP"
],
"width": 220,
"height": 160,
"inputs": [
{
"x": 0,
"y": 40,
"side": "left"
},
{
"x": 0,
"y": 80,
"side": "left"
},
{
"x": 0,
"y": 120,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"TMin": "",
"TMax": "",
"YMin": "",
"YMax": "",
"width": 220,
"height": 160,
"ShowTickLabels": false
},
"render": {
"type": "plot",
"path": "M{axisX} {axisTop} L{axisX} {axisY} L{axisRight-2} {axisY}"
}
},
{
"type": "xyScope",
"icon": "xyScope.svg",
"label": "XY Scope",
"phases": [
"INIT",
"AFTER_STEP"
],
"width": 220,
"height": 160,
"inputs": [
{
"x": 0,
"y": 50,
"side": "left"
},
{
"x": 0,
"y": 110,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"XMin": "",
"XMax": "",
"YMin": "",
"YMax": "",
"width": 220,
"height": 160,
"ShowTickLabels": false
},
"render": {
"type": "plot",
"path": "M{axisX} {axisY} L{axisRight-2} {axisTop+8}"
}
},
{
"type": "xyzScope",
"label": "XYZ Scope",
"icon": "xyzScope.svg",
"phases": [
"INIT",
"AFTER_STEP"
],
"width": 220,
"height": 180,
"inputs": [
{
"x": 0,
"y": 50,
"side": "left"
},
{
"x": 0,
"y": 90,
"side": "left"
},
{
"x": 0,
"y": 130,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"XMin": "",
"XMax": "",
"YMin": "",
"YMax": "",
"ZMin": "",
"ZMax": "",
"width": 220,
"height": 180,
"RotationX": 30,
"RotationY": 45
},
"render": {
"type": "plot",
"path": "M{axisX} {axisY} L{axisRight-2} {axisY-20}"
}
},
{
"type": "fileSink",
"icon": "fileSink.svg",
"label": "Output File",
"phases": [],
"width": 80,
"height": 80,
"inputs": [
{
"x": 0,
"y": 40,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"FileName": "output.csv"
},
"render": {
"type": "image",
"src": "fileSink.svg"
}
},
{
"type": "labelSink",
"icon": "labelSink.svg",
"label": "Label Sink",
"phases": [],
"width": 40,
"height": 40,
"inputs": [
{
"x": 0,
"y": 20,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"GotoTag": "x",
"ShowNode": true
},
"render": {
"type": "math",
"bodyClass": "block-body",
"mathGroupClass": "label-sink-math",
"formula": "{params.GotoTag}"
}
},
{
"type": "display",
"icon": "display.svg",
"label": "Display",
"phases": [
"INIT",
"AFTER_STEP"
],
"width": 120,
"height": 60,
"inputs": [
{
"x": 0,
"y": 30,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"Label": "Display",
"Format": "short",
"Decimation": 1,
"Floating": false
},
"render": {
"type": "math",
"bodyClass": "block-body",
"mathGroupClass": "display-math",
"formula": "\\mathsf{Disp}"
}
},
{
"type": "toWorkspace",
"label": "To Workspace",
"icon": "toWorkspace.svg",
"phases": [
"INIT",
"AFTER_STEP"
],
"width": 80,
"height": 48,
"inputs": [
{
"x": 0,
"y": 24,
"side": "left"
}
],
"outputs": [],
"defaultParams": {
"VariableName": "simout",
"MaxDataPoints": "inf",
"Decimation": 1,
"SaveFormat": "Structure With Time",
"SampleTime": "-1"
},
"render": {
"type": "math",
"formula": "\\mathtt{{params.VariableName}}",
"textSize": 14
}
},
{
"type": "terminator",
"label": "Terminator",
"icon": "terminator.svg",
"phases": [],
"width": 40,
"height": 40,
"inputs": [
{
"x": 0,
"y": 20,
"side": "left"
}
],
"outputs": [],
"defaultParams": {},
"render": {
"type": "image",
"src": "exports/terminator.svg",
"svgMode": "element",
"preserveAspectRatio": "none",
"x": 0,
"y": 0,
"width": 40,
"height": 40
}
},
{
"type": "stopSimulation",
"label": "Stop",
"icon": "stopSimulation.svg",
"phases": [
"AFTER_STEP"
],
"width": 40,
"height": 40,
"inputs": [
{
"x": 0,
"y": 20,
"side": "left"
}
],
"outputs": [],
"defaultParams": {}
}
]
}
Runtimemodules/nflow_blocks/src/cpp/sink/fileSink.cpp
//=============================================================================
// Copyright (c) 2016-present Allan CORNET (Nelson)
//=============================================================================
// This file is part of Nelson.
//=============================================================================
// LICENCE_BLOCK_BEGIN
// SPDX-License-Identifier: LGPL-3.0-or-later
// LICENCE_BLOCK_END
//=============================================================================
#include "SimEngineTypes.hpp"
#include "BlockRegistry.hpp"
#include "FieldNames.hpp"
#include "NFlowBlockDescriptor.hpp"
#include <algorithm>
#include <cstdio>
#include <string>
#include "sink_blocks.hpp"
//=============================================================================
// fileSink: streams its input signal to a CSV file at major steps. INIT
// truncates the file (FileName parameter, default "output.csv") and writes
// the header "t,<id>" (vector inputs: "t,<id>_0,<id>_1,..."); AFTER_STEP
// appends one row per sample. The file is opened and closed per phase so a
// crashed or cancelled run keeps every row written so far. An unwritable
// path is skipped silently (the simulation itself is unaffected).
//
// Code generation lowers the block to a labelSink-shaped model output (a
// column in the generated runner's CSV) instead of an fopen in model.c;
// see the pipeline's fileSink rewrite.
//=============================================================================
namespace {
std::string
fileSinkPath(const Nelson::NFlow::Block& b, const Nelson::NFlow::ValMap& vars)
{
nflow::BlockDescriptor bd(b, vars);
std::string p = bd.paramStr("FileName", "");
if (p.empty()) {
p = bd.paramStr("Filename", "");
}
if (p.empty()) {
p = "output.csv";
}
return p;
}
} // namespace
//=============================================================================
bool
Nelson::NFlow::handleFileSink(SimCtx& ctx, const Block& b, Phase phase)
{
if (phase != Phase::INIT && phase != Phase::AFTER_STEP) {
return false;
}
const std::string path = fileSinkPath(b, ctx.variables);
SigView v = getInputSig(ctx, b.nid, 0);
const int w = std::max(1, v.width);
if (phase == Phase::INIT) {
FILE* f = fopen(path.c_str(), "wt");
if (!f) {
return false;
}
fputs("t", f);
if (w == 1) {
fprintf(f, ",%s", b.id.c_str());
} else {
for (int k = 0; k < w; ++k) {
fprintf(f, ",%s_%d", b.id.c_str(), k);
}
}
fputs("\n", f);
fclose(f);
return false;
}
FILE* f = fopen(path.c_str(), "at");
if (!f) {
return false;
}
fprintf(f, "%.15g", ctx.t);
for (int k = 0; k < w; ++k) {
fprintf(f, ",%.15g", sigAt(v, k));
}
fputs("\n", f);
fclose(f);
return false;
}
//=============================================================================
