Loading tmux on Boot in Linux


tmux is a wonderful tool for displaying virtual consoles on the linux command prompt screen. It’s the next best thing to getting actual GUI windows controllable with a mouse.

Mainly, I use it for ssh purposes. Where I can ssh to a pc that I know has tmux already launched in the background and type.

tmux a

which attaches the session to the on-going tmux background session, allowing you to see everything that is going on in that process. This is especially useful for embedded systems where there are multiple processes launched in the background and you want to monitor them all.

So I have a tmux script launcher.sh here:



#allow re-launch
/usr/bin/tmux has-session -t $SESSION 2> /dev/null && /usr/bin/tmux kill-session -t $SESSION
/usr/bin/tmux -2 new-session -d -s $SESSION

echo "Launching tmux"

/usr/bin/tmux split-window -h
/usr/bin/tmux split-window -v
/usr/bin/tmux select-pane -t 0

/usr/bin/tmux send-keys -t $SESSION.0 "cd /path/to/binary1folder" C-m
/usr/bin/tmux send-keys -t $SESSION.0 "./binary1" C-m

/usr/bin/tmux send-keys -t $SESSION.1 "cd /path/to/binary2folder" C-m
/usr/bin/tmux send-keys -t $SESSION.1 "./binary2" C-m

/usr/bin/tmux send-keys -t $SESSION.2 "cd /path/to/binary3folder" C-m
/usr/bin/tmux send-keys -t $SESSION.2 "./binary3" C-m

This basically opens up , three panes and splits the window horizontally first, then splitting again one of the split windows vertically. It then launches a binary in each of the window panes. I won’ t go too much into the scripting here as there are plenty of resources for doing so, like this.

Configuring tmux to boot on startup on CentOS 7

Normally this should be pretty straightforward, but I ran into some hiccups.


sudo nano /etc/rc.local

And edit the rc.local file to include

su -c /path/toyourscript/launcher.sh -l your_user_id

-l your_user_id means that you do the launch of the script launcher.sh as the user your_user_id.

Make sure your rc.local is executable.

sudo chmod +x /etc/rc.local

And by right it should launch when CentOS boots, launching launcher.sh in the background which in turn launches tmux. However, I found that one of the abrt startup scripts, abrt-console-notification.sh was interfering with the launching of the tmux process/binaries. It would hang at the console terminal of the tmux screens. Doing the following resolved the problem for me.

cd /etc/profile.d/
chmod -r abrt-console-notification.sh

Basically, make abrt-console-notification.sh non-readable, allowing the profile.d startup process to skip over this particular script. It’s kind of a hack, but it worked. I reckon at most I don’t get the automatic bug reporting tool notifications at the console. Note that this script is run depending on what type of installation you chose when installing CentOS. I think that the minimal installl doesn’t run into this issue.

Hope this it useful to you, let me know!

ps. Here’s a tmux cheat sheet. https://gist.githubusercontent.com/afair/3489752/raw/e7106ac93c8f9602d3843696692a87cfb43c2d21/tmux.cheat

CentOS7 – Setting Static IP (Persistent)

Say your device name is ifcfg-eth0
Edit/create  /etc/sysconfig/network-scripts/ifcfg-eth0, enter:

# cat /etc/sysconfig/network-scripts/ifcfg-eth0

Sample static ip configuration:


Reboot, and type ifconfig – you should see the network being assigned the static ip.

More Efficient ifftshift / fftshift in C++


Previously I touched upon ifftshift and fftshift in this post. https://kerpanic.wordpress.com/2016/01/15/matlab-circshift-equivalent-in-c-c/ . I’ve come to realize that there are better ways to implement fftshift and iftshift using simple memory swapping. Note that you have to pre-allocate the appropriate amount of memory for T*out before calling this function.

//-- Does 1D fftshift 
template<typename T>
inline void fftshift1D(T *in, T *out, int ydim)
 int pivot = (ydim % 2 == 0) ? (ydim / 2) : ((ydim - 1) / 2);
 int rightHalf = ydim-pivot;
 int leftHalf = pivot;
 memcpy(out, in+(pivot), sizeof(T)*rightHalf);
 memcpy(out+rightHalf, in, sizeof(T)*leftHalf);

//-- Does 1D ifftshift
//-- Note: T* out must already by memory allocated!!
template<typename T>
inline void ifftshift1D(T *in, T *out, int ydim)
 int pivot = (ydim % 2 == 0) ? (ydim / 2) : ((ydim + 1) / 2);

 int rightHalf = ydim-pivot;
 int leftHalf = pivot;
 memcpy(out, in+(pivot), sizeof(T)*rightHalf);
 memcpy(out+rightHalf, in, sizeof(T)*leftHalf);


Hope this helps! It is good as  a Matlab C++ equivalent.

If you want to do 2D you will have to fftshift first, transpose the matrix, then fftshift it again. Then transpose back to the original matrix form.

Also, a better circshift would be to use C++’s in-built std::rotate

template<typename T>
inline void circshift1D_IP(T *in, int ydim, int yshift)
 if (yshift == 0)

 if (yshift > 0) // shift right
 std::rotate(&in[0], &in[ydim - yshift - 1], &in[ydim - 1]);
 else if (yshift < 0) // shift left
 yshift = abs(yshift);
 std::rotate(&in[0], &in[yshift], &in[ydim - 1]);


How to add Eclipse (or any program) as Launcher in Gnome 3

For some reason unbeknownst to be, Gnome 3 has made it much harder for one to add Eclipse as a launcher under the Applications menu.
Here’s how you can do it.

1. > yum install alacarte
2. You should now see a program called Main Menu somewhere under your applications.
3. Click on Main Menu and create the launcher in the appropriate location.
4. Now the launcher will be shown in the category you created it in. You can now add it to favourites, etc. In case you missed it, in Gnome 3, you have to add applications to your favourites by first moving your mouse to the top left to show the new menu, then searching for your application and dragging it to the left bar.

Oh, and do you miss the quick launcher on the top left of the screen?
Install this extension -> http://frippery.org/extensions/

Then go to :
Utilities->Tweak Tool->Shell Extensions->Frippery panel favourites


Gnome 3 !! Why??