C File I/O. Need asistance.

Thetargos · 02-22-2004, 11:51 PM

Hi all, again me... Although I have knowledge of the C language, I think my I/O on files is way basic for what I need/want to do. My problem is that I have made a BASH script to do a series of tasks, with a nice user interface (Ok, just messages going by asking for user interaction). Anyway, this program depended on file interaction, because after its execution it would generate a specially formatted text file with various information:

Linux version (uname -smrp)
Memory
Graphics
etc.

In a C program, how would I get all this information?

I'd like now to make the same but with a nice Graphical User Interface, where the user may enter all the neede data (the questions of before) and then just let the program execute and verify see the output from that file... I just don't know where to start...

My biggest problem is that I would not know how to edit a text file in a specific location (for example similar to a find/replace function in a text editor.

I want to use GTK, by the way. Thanks for any info.

Darktyco · 02-23-2004, 12:19 AM

If I were you I'd get all that information out of /proc. Specifically memory out of /proc/meminfo and linux version from /proc/sys/kernel/osrelease. I'm not sure about the graphics information, are you looking for info on the device or info on the drivers?

Thetargos · 02-23-2004, 12:24 AM

Quote:

Originally posted by Darktyco
I'm not sure about the graphics information, are you looking for info on the device or info on the drivers?

If it's possible about both. I'm particularly interested on the Renderer string (as reported by glxinfo under OpenGL renderer) and the OpenGL version (since there is posted the driver version). In my BASH script I used the commands with the aid of grep and gawk, but in C how would I accomplish that... I'm trying to

as much as I can... But still I have no clue.

jtshaw · 02-23-2004, 07:26 AM

The uname stuff is best taken from the uname function in sys/utsname.h. It would be faster to get it that way then to read/parse the proc files. Read the man page (man 2 uname) to figure out how to use it.

As far as that grapics information, I am guessing that the OpenGL libraries would have functions to get that information.

Thetargos · 02-23-2004, 02:19 PM

Thanks for the reply, I'll keep looking.

jtshaw · 02-23-2004, 02:49 PM

Check out the Xfree Library Functions. I saw a few that might be helpful at a quick glance like "ScreenOfDisplay", "ServerVendor", and 'VendorRelease".

dakensta · 02-23-2004, 04:43 PM

Call
const GLubyte *glGetString (GLenum name)

and link to libGL.

The manpage will give you the name arguments you require.

Thetargos · 02-23-2004, 04:44 PM

Thanks!

Thetargos · 02-23-2004, 08:16 PM

Yes, this glGetString () function is what I need... I just don't seem to find where is it defined... I guess I should include gl.h or something?

dakensta · 02-24-2004, 05:42 AM

Yes, but it is a bit more complicated than that, I am afraid.

gl.h is probably in /usr/include/GL/ ... make sure you have the opengl-dev package or whatever RedHat call it nowadays.

However, to make the call, OpenGL must first be initialised and that is performed by the windowing system not OpenGL :-(

You are already using GTK and there are OpenGL widgets for that (gtkglext and gtkglarea, I believe) and there is GLX which is the OpenGL interface to XWindows, which would cover this.

I think the easiest thing for you to do is to use glut, which is a platform independent OpenGl rendering toolkit and extremely easy to use - at least just to get started. The same underlying calls can be made by GTK, raw XWindows or whatever. This is quickest and easiest to give you an example and I am lazy.

Example using glut

You will need to #include <GL/glut.h> which also brings in gl.h and you will need to link to libglut.so.

Write a function that calls glutInit() and glutCreateWindow() - this will perform the necessary initialisation and then call glGetString() to get the information you want. The window will not be displayed and you can then use the information as you desire. Then glutDestroyWindow() the window and return the string.
A c++ example:

Code:

#include <iostream>
#include <GL/glut.h>

int main( int argc, char *argv[] )
{
  glutInit( &argc, argv );                  
  int win=glutCreateWindow( "Invisible" );
  std::cout << glGetString( GL_VENDOR ) << '\n';
  glutDestroyWindow( win );
}

Built with: g++ info.cpp -o oglinfo -lglut

Disclaimer: I don't know all the internals of glut, it's just useful sometimes, but you should get the result you want - it runs without the glutInit() call but the manual says this is needed - go figure!

reference: http://www.opengl.org/resources/libr...ec3/spec3.html

Thetargos · 02-24-2004, 05:53 AM

Thanks a lot! I'll use your example as a guidelines for calling it from within a GTK2 window. I hope it works...