`libglew` is just the library, but not the development files (headers). You need to install those separately. The package name on Debian based systems is `libglew-dev`
and for fedora(and possibly its derivatives)  it is `glew-devel`

Run the following command:

    sudo apt-get install libglew-dev

How to convert int (4 bytes) to hex (&quot;`XX XX XX XX`&quot;) without cycles?

for example: 

    i=13 hex=&quot;00 00 00 0D&quot;

`i.ToString(&quot;X&quot;)` returns `&quot;D&quot;`, but I need a 4-bytes hex value.

Convert int to hex with leading zeros

I have an `if` statement:

    if (inventory.contains(&quot;bread&quot;))

But now I want to check

* if `inventory` contains &quot;bread&quot;
* but does not contain &quot;water&quot;.

How can I do this?

Opposite of .contains (does not contain)

I installed OpenGL onto my computer running Linux Mint following the instructions on [this tutorial](http://anytimeir.wordpress.com/2012/05/16/installing-opengl-development-environment-in-ubuntu/). I am trying to compile a program that uses OpenGL, but I&#39;m getting a compile error: `fatal error: GL/glew.h: No such file or directory`. I check the /usr/include/GL folder, and glew.h is indeed missing. I don&#39;t know why it&#39;s missing, because I did the command `sudo apt-get install libglew1.5` and it gives the output:

    Reading package lists... Done
    Building dependency tree       
    Reading state information... Done
    libglew1.5 is already the newest version.
    0 upgraded, 0 newly installed, 0 to remove and 465 not upgraded.

Why is the glew.h file missing?

compiling OpenGL program GL/glew.h missing

I installed OpenGL onto my computer running Linux Mint following the instructions on <a href="http://anytimeir.wordpress.com/2012/05/16/installing-opengl-development-environment-in-ubuntu/" target="_blank" rel="noopener noreferrer">this tutorial</a>. I am trying to compile a program that uses OpenGL, but I'm getting a compile error: <code>fatal error: GL/glew.h: No such file or directory</code>. I check the /usr/include/GL folder, and glew.h is indeed missing. I don't know why it's missing, because I did the command <code>sudo apt-get install libglew1.5</code> and it gives the output:
<pre><code class="hljs language-csharp">Reading package lists... Done
Building dependency tree 
Reading state information... Done
libglew1.5 is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 465 not upgraded.
</code></pre>
Why is the glew.h file missing?

Given the size of a file in bytes, I want to format it with **[IEC (binary) prefixes][1]** to **3 [significant figures][2] with trailing zeros**, e.g. 1883954 becomes 1.80M.

Floating-point arithmetic isn&#39;t supported in bash, so I used awk instead. The problem is I don&#39;t how to keep the trailing zeros. Current solution:

    if [ $size -ge 1048576 ]
    then
        size=$(awk &#39;BEGIN {printf &quot;%.3g&quot;,&#39;$size&#39;/1048576}&#39;)M
    elif [ $size -ge 1024 ]
    then
        size=$(awk &#39;BEGIN {printf &quot;%.3g&quot;,&#39;$size&#39;/1024}&#39;)K
    fi
(The files aren&#39;t that big so I don&#39;t have to consider bigger units.)

Edit: There&#39;s another problem with this. See Adrian Fr&#252;hwirth&#39;s comment below.


  [1]: https://en.wikipedia.org/wiki/Binary_prefix
  [2]: http://en.wikipedia.org/wiki/Significant_figures

File size in human readable format

I have written a small program that interacts with a server on a specific port. The program works fine, but:

Once the program terminated unexpectedly, and ever since that socket connection is shown in `CLOSE_WAIT` state. If I try to run a program it hangs and I have to force it close, which accumulates even *more* `CLOSE_WAIT` socket connections.

Is there a way to flush these connections?

How do I remove a CLOSE_WAIT socket connection

I&#39;m using `sed` for updating my JSON configuration file in the runtime.
Sometimes, when the pattern doesn&#39;t match in the JSON file, `sed` still exits with return code 0.

Returning 0 means successful completion, but why does `sed` return 0 if it doesn&#39;t find the proper pattern and update the file? Is there a workaround for that?

Return value of sed for no match

I&#39;m trying to implement the FUSE filesystem.  I am receiving this error:

&gt; cannot access MountDir: Transport endpoint is not connected

This the relevant parts of the program. There are two directories, `MirrorDir` and `MountDir`, that exist withing the same directory as all of the code. I am calling the program like this:

    ./myFS -o nonempty -o allow_other MirrorDir MountDir


Can anyone see what I am doing wrong?

    static struct fuse_operations xmp_oper = {
    	.getattr	= xmp_getattr,
    	.readdir	= xmp_readdir,
    	.open		= xmp_open,
    	.read		= xmp_read,
    };
    
    int main(int argc, char *argv[]) {
    	int fuse_stat;
    	char* mirrorDir;
    
    	mirrorDir = malloc(sizeof(strlen(argv[argc-2]+1)));
    	if (mirrorDir == NULL) {
    		perror(&quot;main calloc&quot;);
    		abort();
    	}
    
    	// Pull the rootdir out of the argument list and save it in my internal data
    	mirrorDir = realpath(argv[argc-2], NULL);
    
        argv[argc-2] = argv[argc-1];
        argv[argc-1] = NULL;
        argc--;
    
    	// turn over control to fuse
    	fprintf(stderr, &quot;about to call fuse_main\n&quot;);	
    	fuse_stat = fuse_main(argc, argv, &amp;xmp_oper, mirrorDir);
    	fprintf(stderr, &quot;fuse_main returned %d\n&quot;, fuse_stat);
    	return fuse_stat;
    }

FUSE error: Transport endpoint is not connected

I have written a code in python which uses / to make a particular file in a folder, if I want to use the code in windows it will not work, is there a way by which I can use the code in Windows and Linux.

In python I am using this code:

    pathfile=os.path.dirname(templateFile)
    rootTree.write(&#39;&#39;+pathfile+&#39;/output/log.txt&#39;)

When I will use my code in suppose windows machine my code will not work.

How do I use &quot;/&quot; (directory separator) in both Linux and Windows?

How to use &quot;/&quot; (directory separator) in both Linux and Windows in Python?

I know OpenCL gives control of the GPU&#39;s memory architecture and thus allows better optimization, but, leaving this aside, can we use Compute Shaders for vector operations (addition, multiplication, inversion, etc.)?




What is the difference between OpenCL and OpenGL&#39;s compute shader?

I wonder about the `gluPerspective` parameters.

In all examples I see `fovy` is set to around 45-60degrees
I&#39;ve tried to set it to different values and the object just disappears 
what&#39;s the explanation for it? 

The `aspect` value should always be the ratio? why would one change it?

`zNear, zFar` - once again the usual values are around 10 and 500+ what does it reflect?

gluPerspective parameters- what do they mean?

Should I prefer to calculate matrices on the CPU or GPU? 

Let&#39;s say I have the following matrices `P * V * M` , should I calculate them on the CPU so that I can send the final matrix to the GPU (GLSL) or should I send those three matrices separately to the GPU so that GLSL can calculate the final matrix?

I mean in this case GLSL would have to calculate the MVP matrix for every vertex, so it is probably faster to precompute it on the CPU. 

But let&#39;s say that GLSL only has to calculate he MVP matrix once, would the GPU calculate the final matrix faster than the CPU?

Should I calculate matrices on the GPU or on the CPU?

I&#39;m getting thoroughly confused over matrix definitions. I have a matrix class, which holds a `float[16]` which I assumed is row-major, based on the following observations:

    float matrixA[16] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
    float matrixB[4][4] = { { 0, 1, 2, 3 }, { 4, 5, 6, 7 }, { 8, 9, 10, 11 }, { 12, 13, 14, 15 } };

`matrixA` and `matrixB` both have the same linear layout in memory (i.e. all numbers are in order). According to http://en.wikipedia.org/wiki/Row-major_order this indicates a row-major layout.

    matrixA[0] == matrixB[0][0];
    matrixA[3] == matrixB[0][3];
    matrixA[4] == matrixB[1][0];
    matrixA[7] == matrixB[1][3];

Therefore, `matrixB[0]` = row 0, `matrixB[1]` = row 1, etc. Again, this indicates row-major layout.

My problem / confusion comes when I create a translation matrix which looks like:  

    1, 0, 0, transX
    0, 1, 0, transY
    0, 0, 1, transZ
    0, 0, 0, 1

Which is laid out in memory as, `{ 1, 0, 0, transX, 0, 1, 0, transY, 0, 0, 1, transZ, 0, 0, 0, 1 }`.

Then when I call [glUniformMatrix4fv][1], I need to set the transpose flag to GL_FALSE, indicating that it&#39;s column-major, else transforms such as translate / scale etc don&#39;t get applied correctly:

&gt; If transpose is GL_FALSE, each matrix is assumed to be supplied in
&gt; column major order. If transpose is GL_TRUE, each matrix is assumed to
&gt; be supplied in row major order. 

Why does my matrix, which appears to be row-major, need to be passed to OpenGL as column-major?


  [1]: http://www.opengl.org/sdk/docs/man3/xhtml/glUniform.xml

Confusion between C++ and OpenGL matrix order (row-major vs column-major)

I have a calibrated camera (intrinsic matrix and distortion coefficients) and I want to know the camera position knowing some 3d points and their corresponding points in the image (2d points).

I know that `cv::solvePnP` could help me, and after reading [this][1] and [this][2] I understand that I the outputs of solvePnP `rvec` and `tvec` are the rotation and translation of the object in camera coordinate system.

So I need to find out the camera rotation/translation in the world coordinate system.

From the links above it seems that the code is straightforward, in python:

    found,rvec,tvec = cv2.solvePnP(object_3d_points, object_2d_points, camera_matrix, dist_coefs)
    rotM = cv2.Rodrigues(rvec)[0]
    cameraPosition = -np.matrix(rotM).T * np.matrix(tvec)

I don&#39;t know python/numpy stuffs (I&#39;m using C++) but this does not make a lot of sense to me:

 - rvec, tvec output from solvePnP are 3x1 matrix, 3 element vectors
 - cv2.Rodrigues(rvec) is a 3x3 matrix
 - cv2.Rodrigues(rvec)[0] is a 3x1 matrix, 3 element vectors
 - cameraPosition is a 3x1 * 1x3 matrix multiplication that is a.. 3x3 matrix. how can I use this in opengl with simple `glTranslatef` and `glRotate` calls?

  [1]: https://stackoverflow.com/questions/14444433/calculate-camera-world-position-with-opencv-python
  [2]: https://stackoverflow.com/questions/14515200/python-opencv-solvepnp-yields-wrong-translation-vector?lq=1

Content Type	Original Author	Original Content on Stackoverflow
Question	rurouniwallace	View Question on Stackoverflow
Solution 1 - Linux	datenwolf	View Answer on Stackoverflow
Solution 2 - Linux	androidwifi	View Answer on Stackoverflow

compiling OpenGL program GL/glew.h missing

Linux Problem Overview

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Solution 1 - Linux

Solution 2 - Linux

Opposite of .contains (does not contain)

Convert int to hex with leading zeros

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