Posts Tagged ‘secs’

How to set a crontab to execute commands on a seconds time interval on GNU / Linux and FreeBSD

Sunday, October 30th, 2011

Reading Time: 2minutes
Have you ever been in need to execute some commands scheduled via a crontab, every let’s say 5 seconds?, naturally this is not possible with crontab, however adding a small shell script to loop and execute a command or commands every 5 seconds and setting it up to execute once in a minute through crontab makes this possible.
Here is an example shell script that does execute commands every 5 seconds:

for i in $(echo 1 2 3 4 5 6 7 8 9 10 11); do
sleep 5;
$command1_to_exec; $command2_to_exec;

This script will issue a sleep every 5 seconds and execute the two commands defined as $command1_to_exec and $command2_to_exec

Copy paste the script to a file or fetch from here

The script can easily be modified to execute on any seconds interval delay, the record to put on cron to use with this script should look something like:

# echo '* * * * * /path/to/' | crontab -

Where of course /path/to/ needs to be modified to a proper script name and path location.

Another way to do the on a number of seconds program / command schedule without using cron at all is setting up an endless loop to run/refresh via /etc/inittab with a number of predefined commands inside. An example endless loop script to run via inittab would look something like:

while [ 1 ]; do
sleep 5;

To run the above sample never ending script using inittab, one needs to add to the end of inittab, some line like:


A quick way to add the line from consone would be with echo:

echo 'mine:234:respawn:/path/to/script' >> /etc/inittab

Of course the proper paths, should be put in:

Then to load up the newly added inittab line, inittab needs to be reloaded with cmd:

# init q

I've also red, some other methods suggested to run programs on a periodic seconds basis using just cron, what I found in's  as a thread proposed as a solution is:

* * * * * /foo/bar/your_script
* * * * * sleep 15; /foo/bar/your_script
* * * * * sleep 30; /foo/bar/your_script
* * * * * sleep 45; /foo/bar/your_script

One guy, even suggested a shorted way with cron:

0/15 * * * * * /path/to/my/script

Improve your night sleep when using PC with Windows XP late at night with F.lux

Tuesday, February 26th, 2013

Reading Time: < 1minute

f.lux auto detect timezone geographic location after install screenshot microsoft windows XP

After testing F.lux on Mac OS X, I decided to install it and test it on a friend's Windows XP OS. Up is a screenshot from the program right after installed.

Just like on MAC OS XF.lux auto set the Geographic Location and started changing the Gamma of the screen to reddish at night. As you can see the change of Screen Color gamma can be set in various intervals with default of auto changing monitor backlid gamma every 20 secs.

On early day, when usually outside you see the day light because Sun Light shines on our planet, the color gamma is auto-configured to the normal light one.
I think in short future all computer vendors should think of embedding F.lux or some similar application to every Desktop PC, laptop, Phone and Tablet.


f.lux settings improve night sleep auto set monitor gamma ms windows xp

When F.lux is active a tiny icon with the F.Lux logo is visible on Taskbar like in below screenshot. From there you can view f.lux settings, see in what Color gamma mode the program works at present or to manually set custom color gamma. Enjoy

How to take area screenshots in GNOME – Take quick area selection screenshots in G* / Linux and BSD

Thursday, March 15th, 2012

Reading Time: 7minutes

Quick Area screenshot in GNOME how to make quick area selection screenshots in Linux and FreeBSD gnome-screenshot shot

Often when, you do something on your PC, you need to make a quick screenshot of a screen area.. Yes GNOME's feature to take complete screenshots of Screen with Print Screen SysRQ and consequential picture edit with GIMP is one way, but this is far away from quick. This method to chop out of a complete display screenshot usually takes from 40 secs to 1 minute to properly cut and save a selection of the whole picture.
Another common use, that I love in GNOME is the ALT + Print Screen SysRQ key combination. alt+ print scr sysrq is handy while taking a single window screenshot is desired. Anyways often you only need to make a screenshot of a tiny area of the screen. Many people might think this is not possible currently in GNOME, but they will be wrong as there are no impossible but hard things to achieve on Linux / FreeBSD 😉

There are at least two ways using a predefined command for taking quick area screen snapshot.

1. Taking quick area screenshot by using ImageMagick's import command

To use import you will need to have installed ImageMagickswiss army knife of command line image manipulation 😉
For area screenshot with import, press ALT+F2 and type inside Run Application box:

Screenshot GNOME run application GNU / Linux Debian ImageMagick import area screenshot

import -frame screenshot.png

Now make the selection of the exact screen area you would like to screeshot in file screenshot.png
Note that screenshot.png file will be saved by default in your home directory as it is read from $HOME shell variable:

hipo@noah:~$ echo $HOME/home/hipo
hipo@noah:~$ ls -al screenshot.png
-rw-r--r-- 1 hipo hipo 4950 Mar 14 21:11 screenshot.png

You see my $HOME equals /home/hipo, therefore screenshot.png just grabbed is saved in there.

One downside of taking the screenshot with import is that picture snapshot is not further edittable, if it has to be further processed with GIMP or some other graphic editor program.

In the screenshot, below I show you one screen area of my XMMS taken with import -frame screenshot.png cmd:

XMMS Screen Area Screenshot import screenshot

Trying to open the screenshot.png, file with GIMP displays the following error in GIMP:

PNG image message PNG the file specifies offset that caused the layer to be positioned outiside image GIMP screenshot

Not all area snapshots taken with import -frame, create this issue sometimes screenshots are opening in GIMP but only area of the screenshot.png is visible in gimp.

Thanksfull, there is work around to this issue by converting the import generated PNG format picture to JPEG with ImageMagick's convert and then edit the .JPEG with GIMP etc.:

hipo@noah:~$ convert screenshot.png screenshot.jpg

Hence to permanently work around it, in case you intend to apply (GIMP modifications), once area snapshot is made instruct import to save its output picture in .jpeg, e.g.:

hipo@noah:~$ import -frame screenshot.jpeg

2. Taking quick area screenshot using gnome-screenshot cmd

Once again invoke the GNOME command Launcher by pressing Alt+F2 (holding alt and pressing F2) and type in the launch box:

gnome-screenshot -a

gnome-screenshot Run Application in GNOME 2.30 on Debian GNU / Linux

Below is a small area from my desktop, chopped with gnome-screenshot 🙂

GNOME desktop area chop screenshot with gnome-screenshot on my home Debian Linux

You see on above screenshot a tiny (picture) icon one of the greatest, if not the greatest bulgarian saint – saint John of Rila. St. John's lived as hermit for many years in Rila mountain and by God's grace possessed incorruptable body. His incorruptable body is still kept and can be venerated in Rila Monastery. The monastery is located 160 km from Bulgaria's capital city Sofia

St. Johns first Bulgarian established monastery Rila Monastery is currently the biggest functioing monastery in Bulgaria. The saints monastery is considered one of the most holy places in Bulgaria. If you have a travel or plan a holiday in Bulgaria, I warmly recommend you go there and venerate the saint incorruptable relics.

3. Binding keys to allow quick area screenshot taking with gnome-screenshot in GNOME

This configuration is for GNOME 2.x and is tested to work on my Debian (Squeeze 6.0), GNOME ver. 2.30.2, it should work in earlier Ubuntu versions shipped with GNOME 2.2.xx too. As I've red on the Internet it works well with Ubuntu 10.10Binding a key for screenshot area grab, should be working properly also on any GNOME 2.2.x supporting OS, including the BSD family OSes (FreeBSD, OpenBSD, NetBSD)

a) setting gnome-screenshot key binding for interactive screenshot area grab

Navigate the mouse cursor to GNOME main menus panel in left top, where you see (Applications, Places, System).
Therein use menus:

System -> Preferences -> Keybord Shortcuts -> Add ->

Alternatively if you prefer you can directly invoke the Keyboard Shortcuts configuration with command:

hipo@noah:~$ gnome-keybinding-properties

Further on, assign a shortcut by filling in something like:

name: grab-screen-area
command: gnome-screenshot -i -a

GNOME add keyboard shortcut map key for area interactive screenshot

press Apply and next map a key to the new defined key binding:

GNOME add keyboard shortcut map key

Under the Shortcut column click on Disabled and assign some key combination to invoke the cmd for example Ctrl+F4

The command gnome-screenshot -i makes gnome-screenshot, show interactive make screenshot dialog like the one in below screenshot.

GNOME screenshot interactive screenshot select area grab shot

b) creating gnome-screenshot -a area screenshot key binding for quick area screenshots "on the fly"

The procedure is precisely the same as with adding interactive screenshot; Under Keyboard Shortcuts GNOME config assign new key binding by pressing Add button and adding:

name: grab-screen-area1
command: gnome-screenshot -a

Once again in Shortcut column in line starting with grab-screen-area1 add your desired key switch. I personally like Ctrl+Print Screen SysRQ as it is close to the default GNOME key combination assigned for taking screenshot for a Windows Alt+Print SysRq

It was logical, that this key binding should work and a direct selection mouse cursor to appear once Alt+Print SysRQ is pressed, however for some reason this is not working (hmm, maybe due to bug) ??

Thanksfully it is always possible to substitute the just assignedgnome-screenshot -a key binding with import -frame /home/hipo/Desktop/screenshot.png

If you have followed literally my article so far and you did tried to place a bind for gnome-screenshot -a, modifty grab-screen-area1 to be something like:

name: grab-screen-area1
command: import -frame /home/hipo/Desktop/screenshot.png

Where modify the path /home/hipo/Desktop/screenshot.png, to wherever you prefer the region screep capture to be stored.

c) bind keys for delayed screenshot

This also a handy binding, especially if you every now and then need to make screenshots of screen with a few secs interval.
Add one more keyboard shortcut;

name: grab-screen-area2
command: gnome-screenshot -d 5

Assign a key to make a screenshot of the active display after a delay of 5 seconds. I prefer Ctrl+F5

Onwards every time you would like to make an area screenshot, just use the defined keys:

Ctrl+F4 - will prompt you interactively for the precise type of screenshot you would like to take
Ctrl+Print SysRQ - will prompt you for a direct area to select and once selected will immediately screenshot it
Ctrl+F5 - would do delayed screenshot of entire screen after a delay of 5 seconds

4. Adding border and drop shadow effects with gnome-screenshot Actually, there is plenty of interesting things to do with Screenshots which I never thought were possible.
While reading gnome-screenshot's man page, I've stumbled to an interesting argument:

-e, --effect=EFFECT,
Add an effect to the outside of the screenshot border. EFFECT can be ``shadow'' (adding drop shadow), ``border'' (adding
rectangular space around the screenshot) or ``none'' (no effect). Default is ``none''.

This would have been a nice feature but as of time of writting this article, untofrtunately it is not working in GNOME 2.30.2. I'm not sure if this is a local Debian bug, however I suspect on other Linux distributions with different GNOME build configuration, this features might be working well. My guess here is drop shadow effect and border effect are not working because, gnome-screenshot was compiled without (support for ImageMagick?).
Anyways the way the feature is supposed to be work is by invoking commands:

hipo@noah:~$ gnome-screenshot --border-effect=shadow
hipo@noah:~$ nome-screenshot --border-effect=border

The same basic effects, are also available through GIMP's menus:

Image -> Effects

5. Setting default behaviour of gnome-screenshot in gconf-editor GConf (Gnome config registry db)

Experienced, GNOME users should already know about the existence of gconf-editor and the gnome registry database. For those who have don't, coming from MS-Windows background gconf-editor is GNOME (graphical environment) equivalent to Microsoft Windows registry regedit command

gconf-editor can be used to atune the way the screenshots are taken by default. To do so, launch gconf-editor cmd and follow to sub-structure:

/ -> apps -> gnome-screenshot

gconf-editor GNOME screenshot border effect none default gnome-screenshot gnome behaviour

The settings in above screenshot are configurations which are used by default by gnome-screenshot, right after install.
You can play with the options to change the default way PrintScreen SysRQ key press will take screenshots.
Here is one example for changing the gnome-screenshot default GNOME behaviour:

GConf Editor GNOME screenshot, border effect drop shadow and include border option set on Linux Debian

As you can see in above screenshot, I've changed my default gnome-screenshot snap taking to include a drop shadow effect:
Name | Value
border_effect | shadow include_border | (tick on)
last_save_directory | file://home/hipo/Desktop

As you see you can also control, where by default gnome-screenshot will save its screenshots, by default, its saved in $HOME/Desktop
. If you prefer some custom directory to only contain Screenshots taken for instance $HOME/Screenshots, create the directory:
hipo@noah:~$ mkdir ~/Screenshots

and then change the value for last_save_directory gconf var:

last_save_directory | file://home/hipo/Screenshots

Once settings are applied screenshots with Print Screen SysRQ key will be made with Shadow Border effect and saved in /home/hipo/Screenshots

Strangely enough, changing gnome-screenshot default screenshotting values to include screenshot effects like drop shadow or screenshot border effect works just fine.
Even though gnome-screenshot –border-effect=shadow and gnome-screenshot –border-effect=border doesn't directly affect the current screenshot to be made, I've later noticed writting this two commands in the gnome-terminal, does change the border settings for gconf-editor screenshot border.

If you enjoyed, this article and you intend to become "a professional screnshotter" :), you might also enjoy my two other articles:

Happy screenshotting 😉

Kill everything that Moves (KETM) an arcade spaceship Tyrian GNU / Linux game

Saturday, January 7th, 2012

Reading Time: 3minutes

I always love so much to go back to the times, when games were games and people had still valued words like moral and respect.
In that great days of old school computing, we used to play the awesome old schools Tyrian and the Nintendo 1941 game (hopefully some still remember).

KETM Tyrian like Old School 2d Spaceship shooter awesome

For all who don't Tyrian is one of the best Spaceship Arcades of all times!, and especially for DOS operating system the best I've personally seen.

Recently I was checking the arcade games available for install on my Debian GNU / Linux and happily come across a game called KETM.

KETM acronym stands for the memorizable KILL EVERYTHING THAT MOVES and is free software distributed game under GPL.
The original creation idea was probably to resemble the so famous in the '90s spaceshooter games.

KETM is pretty addictive just like tyrian and has santimental meaning for me since it brings me memories for my arcade gaming years 😉

The game is easy to play and has a feeling of "diversity" especially in type of weapons your ship can obtain and use against enemies.

The powerups you get is quite plenty compared to the enemy ship types you should destroy 😉 In overall the game is quite easy to play, this however is also a good thing, as you can play more smoothly without dying every few secs like it is in so many arcade games…

The game has only 4 game levels and on each level end there is a big spaceship "the boss" which is the last in line to destroy in the tradition of the 2d arcade games.

KETM Tyrian like Linux Debian arcade game

Kill Everything That Moves is available for Debian and Ubuntu as a deb installable with apt. To install the game on Debian and Ubuntu

debian:~# apt-get install ketm

ketm's official latest available source and binary of time of writting this article is at version 0.6 and as far as I checked it unfortunately seems like the game development is stucked and the code seems a unmaintained.
I'm sure ketm has a lot of potential en hope somebody will adopt the code and will push further its development.
The game runs by default in the annoying windowed mode, I don't like this so I always run it fullscreen:

Kill Everything that Moves Tyrian like arcade game for Debian Ubuntu Linux

debian:~# ketm -f

KETM also reminds a bit on GEKI 2 / 3, which I have previously blogged about but I found KETM to be more enjoyable than gekis.
I've seen KETM has RPM ports as well so installing the game on fedora will be probably as easy as downloading the respective RPMs fulfilling the RPM package requirements and installing with rpm -i. I would be glad to hear from people who had succesfully run the game on Fedora and other RPM based Linux distributions?

The only thing that prevents the game to feel a bit more awesome (in my view) is the missing sound & music … Even though in the game settings inside the main menu there is an option for Sound On / Off the game runs by default without any sound or music (at least on my Debian).
I hope you will have some fun with KETM just I like I did! 😉
Also if you haven't played Tyrian yet, then I strongly advice you download Tyrian from here and try it out with dosbox (a dos gnu linux / bsd game emulator)

Absolute Game Classics Tyrian native game play with dosbox Linux screenshot

Interesting fact to mention here,  while looking for the native tyrian game info , I found tyrian has an open source version under development called OpenTyrian . I'll check the game and write on it when I have time.

How to install Ubuntu Linux on Acer ASPIRE 5736Z Notebook / Get around the black screen install CD issue

Friday, July 1st, 2011

Reading Time: 2minutes
My sister’s newly bought laptop is Acer Aspire 5736Z . By the default this notebook comes with some kind of Linux distribution Linpus .
Even though this Linpus (crafted Linux especially for Acer notebooks) looked really nice, it prooved to be a piece of shit linux distro.
Linplus was unable to even establish a simple Wireless WPA2 protected connection with my wireless router, not to mention that the physical Linux consoles (CTRL+ALT+F1) were disabled …

This LinPlus was so bad that I couldn’t even launch any type of terminal on it (I was stuck!) so I decided to kill it and make a decent latest Ubuntu 11.04 Install on it.

I was surprised to find out that trying to boot up the Ubuntu 11.04 installer led me to a black screen (black screen of death).

The v Aspire’s 5736Z monitor kept completely blank, where the hard drive was continuously reading (indicating that the Ubuntu installer has properly booted but it couldn’t light up the notebook screen).

A bit of investigation on any issues with this Acer notebook model has led me to a thread in fedora forums:
On this forum the same kind of Linux install problem was described to also occur with ASPIREs 5736Z during a Fedora install.

I just tried the suggested fix and it works like a charm.

The fix goes like this:

1. Invoke the Ubuntu settings parameter Install pre install screen

Just press any button while the Ubuntu installer CD is reading and after few secs the Install options screen should appear, like you see it in below’s screenshot:

Ubuntu Install boot options parameters screen

2. Select the nomodetest Boot CD Ubuntu option

You see in the above screenshot the F6 Other Options . I had toto press F6 and choose the nomodetest boot option to make the Ubuntu be able to further boot up.

After selecting the nomodetest option and pressing on the Install Ubuntu menu option the graphic installer launched succesfully 😉
Hope this small tip to be helpful to some Ubuntu or other Linux user who is trying to install Linux on his Acer Aspire 5736Z
Cheers 😉