I just started few weeks ago with GLSL and I was trying to find the best way to include shader code into my intro.

I found out many ways, the two following ways were easy to use just having a little text converter, but hard to manage changes because you always mistake while entering the separators:

GLchar* vs="void main(void)"
"gl_TexCoord[0] = gl_MultiTexCoord0;"
"gl_Position = ftransform();"

This one is even harder to read:

GLchar *vs_test ="void main()\r\n\
gl_Position = ftransform();\r\n\

But finally, I found a much simpler and good looking way to stringify the shader:

#define STRINGIFY(A)  #A

GLchar* vs_blur=STRINGIFY(
void main()
  gl_TexCoord[0] = gl_MultiTexCoord0;
  gl_Position = ftransform();

More info