How to generate OBJ mesh file if I used GLSL - c++

Question

I want to generate a OBJ file from a code, which using GLSL file to generate mesh, now I can get the vertex information from the code, but how can I extract the triangle information from the .geom.glsl file and export it into a OBJ file?
Also, is there any helper function do to so? if not, how should I write the code to get the points and triangle information from the geom.glsl file?
Here attached the geom.glsl:
#version 400 core
#extension GL_EXT_geometry_shader4 : enable
layout(lines, invocations = 1) in;
layout(triangle_strip, max_vertices = 100) out;
uniform mat4 matLightView;
uniform mat4 matViewProjection;
uniform vec3 lightPos;
uniform vec3 camPos;
uniform int isExplicit;
in vec4 VertPosition[];
in vec4 VertColor[];
in vec3 VertNormal[];
in vec3 VertTexture[];
in float VertLengthTotal[];
in float VertLengthFromBeginning[];
out vec3 GeomNormal;
out vec2 GeomTexCoords;
out float GeomDiffuse;
out float GeomThickness;
out vec4 texCoordA;
out vec4 texCoordB;
const float PI2 = 2 * 3.141592654;
void main()
{
// for(int i=0; i<gl_VerticesIn-1; ++i)
for (int i = 0; i<gl_in.length ()-1; ++i)
{
//Reading Data
vec4 posS = VertPosition[i];
vec4 posT = VertPosition[i+1];
vec3 vS = VertColor[i].xyz;
vec3 vT = VertColor[i+1].xyz;
vec3 tS = VertTexture[i].xyz;
vec3 tT = VertTexture[i+1].xyz;
float thickS = VertColor[i].w;
float thickT = VertColor[i+1].w;
//Computing
vec3 v11 = normalize(vS);
vec3 v12 = normalize(cross(vS, tS));
vec3 v21 = normalize(vT);
vec3 v22 = normalize(cross(vT, tT));
float rS = max(0.0001, thickS);
float rT = max(0.0001, thickT);
int pS = 10;
int pT = 10;
int forMax = 16;
//Light Pos
vec4 lPos = normalize(vec4(-lightPos.x, -lightPos.y, -lightPos.z, 1));
vec3 L = normalize(lPos.xyz);
for(int k=0; k<=forMax; ++k)
{
float angle = k * (PI2 / forMax);
vec3 newPS = posS.xyz + (v11 * sin(angle) + v12 * cos(angle)) * rS;
vec3 newPT = posT.xyz + (v21 * sin(angle) + v22 * cos(angle)) * rT;
float scale = 1.0f;
float texX = float(k) / float(forMax);
float edgeLength = length(posS - posT);
float sTexY = (VertLengthFromBeginning[i] * scale);
float tTexY = (VertLengthFromBeginning[i+1] * scale);
//Source Vertex
vec3 N = normalize(posS.xyz - newPS);
texCoordB = matLightView * vec4(newPS, 1);
GeomNormal = N;
GeomThickness = rS;
GeomDiffuse = rS < 0.0005 ? 0.0f : max(dot(N, L), 0.0);
GeomTexCoords = vec2(texX, sTexY);
gl_Position = matViewProjection * vec4(newPS, 1);
EmitVertex();
//Target Vertex
N = normalize(posT.xyz - newPT);
texCoordB = matLightView * vec4(newPT, 1);
GeomNormal = N;
GeomThickness = rT;
GeomDiffuse = rT < 0.0005 ? 0.0f : max(dot(N, L), 0.0);
GeomTexCoords = vec2(texX, tTexY);
gl_Position = matViewProjection * vec4(newPT, 1);
EmitVertex();
}
}
EndPrimitive();
}
And the vert.glsl:
#version 400 core
#define VERT_POSITION 0
#define VERT_NORMAL 1
#define VERT_COLOR 2
#define VERT_TEXTURE 3
layout(location = VERT_POSITION) in vec4 Position;
layout(location = VERT_NORMAL) in vec4 Normal;
layout(location = VERT_COLOR) in vec4 Color;
layout(location = VERT_TEXTURE) in vec4 Texture;
out vec4 VertPosition;
out vec3 VertNormal;
out vec3 VertTexture;
out vec4 VertColor;
out float VertLengthFromBeginning;
out float VertLengthTotal;
uniform mat4 matModel;
void main()
{
VertPosition = matModel * Position;
VertNormal = Normal.xyz; // Direction
VertColor = Color; // V from PTF, VertColor.w = thick
VertTexture = Texture.xyz; // Tangent
VertLengthFromBeginning = Normal.w; // Global Texture Coordinates
VertLengthTotal = Texture.w; // total length of chain
}
Lots of Thanks!!