howtos


GNU Linux/Bash: A function that splits a word in half

The following function takes one argument – a text file.
The text file should contain one word on each line.
The function reads the text file (argument) line by line.
Then it checks if the line has one word; if this is true, it splits the word in half.
Finally, it prints the two new words with a space between them.

#!/bin/bash

splitWordsInHalf () {
  # This function takes one argument - a text file.
  # The text file contains one word on each line.
  # It reads the text file (argument) line by line.
  # Then it checks if the line contains one word, if this is true, it splits the word in half.
  # Finally, it prints the two new words with a space between them
  while read line
  do
    words=( $line )
    if [ ${#words[@]} == 1 ]
    then
      echo ${line:0:${#line}/2} ${line:${#line}/2}
    fi
  done < $1
}

splitWordsInHalf input.txt

Example

Using the following input file:

banana
apple
ball
car
door

We will get the following output when we execute splitWordsInHalf input.txt:

ban ana
ap ple
ba ll
c ar
do or

Notes

The following parts of the code are in charge of looping on the data of the incoming file. The parameter (the input file) given to the function is translated into the variable $1. The while loop gets one line of text on each iteration and assigns the text to the variable that is named line. You could have chosen any other name that suits you instead of the word line.

splitWordsInHalf () {
  while read line
  do
    ...
  done < $1
}

The next part of the code (words=( $line )) converts the string value that is contained in the line variable into an array of words, and it assigns that array to the variable named words. Then, it counts the number of elements in the array (the number of words in the line) using the following ${#words[@]} and it checks that there is only one item.

words=( $line )
if [ ${#words[@]} == 1 ]
then
  ...
fi

The following line will print two strings. The first string is a sub-string of variable line that is composed by the first half of the value. The second sub-string is the second half of the value contained in the variable named line.

echo ${line:0:${#line}/2} ${line:${#line}/2}

The ${#line} will return the length of the string contained in the variable.

The structure ${VARIABLE:START:END} defines the slice of the string that we want returned.


How to Reset Password on an Ubuntu with LVM

A few days ago, a client tasked us to recover the password of an Ubuntu server 20.04LTS. The machine owner only knew the username but had no idea about the complexity of the password. We’ve asked the client if it was OK for us to reset the password instead of recovering it (meaning that we would not even try to crack the mystery of what the previous password was and just set a new one), and thankfully, the client accepted our request.

The client set up the server using Ubuntu server edition 20.04LTS, and the disk partitions were using LVM (Logical Volume Manager). To our good luck, they were not using encrypted partitions. The procedure we followed to reset the password of that server was like so:

First of all, we shut down the server and booted it with a Live USB of an Ubuntu desktop 20.04LTS. Then we started a terminal and executed the following to get root access on the live system:

sudo su;

Then, we executed pvscan to list all physical volumes and gain some intelligence on which disk we needed to work on:

pvscan;
[email protected]:/home/ubuntu# pvscan
  /dev/sdc: open failed: No medium found
  PV /dev/sda3   VG ubuntu-vg       lvm2 [<3.64 TiB / 3.44 TiB free]
  Total: 1 [<3.64 TiB] / in use: 1 [<3.64 TiB] / in no VG: 0 [0   ]

Following that, we used vgscan to search for all volume groups:

vgscan;
[email protected]:/home/ubuntu# vgscan
  /dev/sdc: open failed: No medium found
  Found volume group "ubuntu-vg" using metadata type lvm2

From these two commands, it was clear that the disk /dev/sda3 contained an LVM partition with the logical volume group name ubuntu-vg. That logical volume group held the server’s filesystem, and it was the place we needed to access to change the user’s password.

So, we used vgchange to change the attributes of the volume group and activate it like so:

vgchange -a y;
[email protected]:/home/ubuntu# vgchange -a y
  /dev/sdc: open failed: No medium found
  /dev/sdc: open failed: No medium found
  1 logical volume(s) in volume group "ubuntu-vg" now active

Using lvscan, we were able to list all logical volumes in all volume groups and verify that we activated the volume group of interest successfully.

lvscan;
[email protected]:/home/ubuntu# lvscan
  /dev/sdc: open failed: No medium found
  ACTIVE            '/dev/ubuntu-vg/ubuntu-lv' [200.00 GiB] inherit

After these steps, we were ready to reset the password of the user finally. We continued to mount the logical volume group like any other disk on the /mnt folder:

mount /dev/ubuntu-vg/ubuntu-lv /mnt/;

Then, we used chroot to change the apparent root directory for the currently running process (and its children). This command allowed our terminal to work inside the logical volume as if we had booted the server OS itself.

chroot /mnt/;

Finally, using the passwd command, we changed the user password as so:

passwd -S bob;

To clean up, we exited the chroot environment:

exit;

Then, we unmounted the logical volume group:

umount /mnt;

And finally, we set the active flag of the volume group to no.

vgchange -a n;

After the above steps, we had safely applied all changes, so we rebooted the machine using its hard drive.


Testing free Text to Speech engines on Ubuntu GNU/Linux

Recently, we decided to test a few free text to speech engines (TtS) on GNU/Linux. We were curious on what the current capabilities that are available as we wanted to create a few videos. To play a bit, we tested espeak, festival and pico. For this reason, we created a text file (called text.txt) and added the following content to it:

I triple E has a lot of scholarships, awards, and opportunities, but it doesn't have a centralized site where members can quickly identify the right ones.
Many problems arise as a result of the lack of this platform.
One crucial issue is that many people are unaware of specific opportunities until it is too late. Many projects are squandered each year because there is insufficient knowledge about these opportunities, resulting in low participation.
Another critical difficulty is having to start over with each application. Many people find it frustrating, and it prevents them from doing so.
The lack of real-time support to answer issues while an applicant is applying is critical, leading to discouragement and abandonment of the application process.
Providing references is a topic that many individuals are uncomfortable with. They are embarrassed to seek references that need to learn new systems and maybe answer the same questions posed in other ways.

Our solution is utilizing the Collabratec platform and storing all of these opportunities there:
Collabratec already has numerous key capabilities in place, lowering development costs.
Each application may have its own community or working group where an applicant can seek special clarifications or support. Collabratec will save money on development by repurposing existing technology. It will also give such features a new purpose.
Through those working groups, experienced members can share their knowledge and potentially coach applicants during their application process. Many members would be willing to help others attain their objectives, especially after they've gone through the process and understand the frustrations others are experiencing. We could utilize badges to reward individuals who aid others and those who apply for these possibilities, which is a frequent practice in Collabratec to make certain members stand out. This approach will assist members in getting to know one another and expanding their network outside their geographic zones, resulting in a genuinely global I triple E experience.
People who create opportunities can utilize the I triple E profile of a user to pre-populate elements of their application. As a result, the applicants' effort will be reduced because they will only fill in the questions related to that particular opportunity.
Without any additional work, the system may reuse earlier references. Assume that a reference has to be updated or validated to ensure that it is still valid. In that situation, the system may send an automatic notification to that person, asking them to approve, alter, or delete their earlier contribution.
Because users can readily share each application form and the corresponding working group information, Collabratec's capabilities as a social network will significantly enhance each opportunity's reach and all related documents, public comments, and discussions.

espeak

We started off with espeak and we used the following commands to test it:

# Command to install espeak;
sudo apt install espeak;
# Command that reads the text.txt file creates an audio file from its content.
espeak -f text.txt -w espeak.wav;

The result from espeak is below:

espeak definitely does not sound human-like. It is a fun tool if you need to create an audio file that sounds robotic! In our case, it was not a solution as we wanted to use a long text, listening to a robotic voice for a lot of time can be tiring.

festival

After that, we tested the text2wave tool of festival as follows:

sudo apt install festival;
cat text.txt | text2wave -o festival.wav;

The results from festival/text2wave are the following:

festival does sound a bit better than espeak, it’s almost smooth but not quite. You can easily tell that this is a computer-generated voice.

pico

Finally, we tested pico utilities. We set it up and used it as follows:

sudo apt install libttspico-utils;
pico2wave -l en-US -w test.wav "$(cat text.txt)";

The results of pico2wave were pretty good! Not perfect but still good! The voice is nearly human-like and fairly smooth. Below is the result of our test:

From the three utilities, pico was the most human-like and it fit our needs more. With this tool, we will be able to create certain videos with narration without being too annoying.

Other information

To create the videos, we used ffmpeg. As in the following commands, we combined the audio wave files with static images that were looped forever.

ffmpeg -loop 1 -i TtS-pico2wave.png -i test.wav -c:a aac -c:v libx264 -pix_fmt yuv420p -shortest TtS-pico2wave.mp4;
ffmpeg -loop 1 -i TtS-espeak.png -i espeak.wav -c:a aac -c:v libx264 -pix_fmt yuv420p -shortest TtS-espeak.mp4;
ffmpeg -loop 1 -i TtS-festival.png -i festival.wav -c:a aac -c:v libx264 -pix_fmt yuv420p -shortest TtS-festival.mp4;

Get execution time in seconds

The following methods demonstrate different methods on how to compute the time a potion of code or script take to complete their execution.

Time Methods - Full Examples (708 downloads)

 

Method 1 – Using date

The following example will calculate the execution time in seconds by subtracting the system date and time in seconds since 1970-01-01 00:00:00 UTC once right before the script goes to the computation part and once right after.

In order to get the system date and time in seconds since 1970-01-01 00:00:00 UTC we use the command date +%s.

Time Methods - Full Examples (708 downloads)

#!/bin/bash

#Print the system date and time in seconds since 1970-01-01 00:00:00 UTC
startTime=$(date +%s);

#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
sleep $(( (RANDOM % 10) + 1 ));

endTime=$(date +%s);

#Subtract endTime from startTime to get the total execution time
totalTime=$(($endTime-$startTime));

echo "Process finished after $totalTime seconds";

exit 0;

Method 2 – Using bash internal SECONDS variable

The following example will calculate the execution time in seconds by reseting the bash internal variable SECONDS to 0, forcing the shell to continue counting from there.

Time Methods - Full Examples (708 downloads)

#!/bin/bash

#This variable expands to the number of seconds since the shell was started.
#We set it to 0, forcing the shell to continue counting from there.
SECONDS=0;

#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
sleep $(( (RANDOM % 10) + 1 ));

echo "Process finished after $SECONDS seconds";

exit 0;

Method 3 – Using bash time

The following example uses the bash time command, which reports the time consumed by a pipeline’s execution.
When time command is executed without its complete path, then the bash built-in time command is executed, instead of the GNU time command. We will use the bash time command in this example and we will use it to run a whole block of commands.
Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).

Time Methods - Full Examples (708 downloads)

#!/bin/bash

#The bash time command reports the time consumed by pipeline's execution
#When time command is executed without its complete path, then the bash built-in time command is executed, instead of the GNU time command.
#We will use the bash time command in this example and we will use it to run a whole block of commands.

#We change the output format of time to print elapsed real time in seconds.
TIMEFORMAT="%E";
#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
totalTime=`time ( sleep $(( (RANDOM % 10) + 1 )) ) 2>&1`;

#Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).
#This will happen as time has build-in more precision than the first two methods presented here.
echo "Process finished after $totalTime seconds";

totalTimeBlock=`time (
	sleep $(( (RANDOM % 10) + 1 ));
	sleep $(( (RANDOM % 10) + 1 ));
) 2>&1`;
echo "Block finished after $totalTimeBlock seconds";

exit 0;

Method 4 – Using GNU time

The GNU time command runs the specified program command with the given arguments.
When time command is executed without its complete path (in our case it was /usr/bin/time), then the bash built-in time command is executed, instead of the GNU time command. To make sure we use the GNU time command, we use which to get the full path of the time command.
Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).

Time Methods - Full Examples (708 downloads)

#!/bin/bash
#The time command runs the specified program command with the given arguments.
#When time command is executed without its complete path (in our case it was /usr/bin/time), then the bash built-in time command is executed, instead of the GNU time command.
#To make sure we use the GNU time command, we use which to get the full path of the time command.
time=`which time`;

#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
#We change the output format of time to print elapsed real time in seconds.
totalTime="$( $time -f '%e' sleep $(( (RANDOM % 10) + 1 )) 2>&1 1>/dev/null )";

#Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).
#This will happen as time has build-in more precision than the first two methods presented here.
echo "Process finished after $totalTime seconds";

exit 0;

Notes

RANDOM internal variable

Each time RANDOM internal variable is referenced, a random integer between 0 and 32767 is generated.

By using the RANDOM variable in this command $(( (RANDOM % 10) + 1 )); we perform a modulo on the random value with the static value 10. This way we force the range of valid values to be between 0 and 9.
Later, we add 1 to that value to shift the range to be between 1 and 10.


HOWTO: Make Terminator Terminal Act Like Guake Terminal in Ubuntu 16.04 LTS (The easy ways) 3

First way to make terminator toggle its visibility using the F12 key (like guake)

  • Start terminator
  • Right click anywhere in the terminal area and click on the Preferences option

terminator-01

  • In the new window, click on the Keybindings tab and scroll down until you find the line that has the following information:
    Name : hide_window
    Action : Toggle window visibility

terminator-02

  • Click on the Keybinding column (3rd column), the value will change to New accelerator..., hit the key combination you want to be used to toggle the visibility of terminator. If you want the same behavior as guake, hit F12. You will see that the value in the Keybinding column will change to F12.
  • Hit the close button to close the settings window.
  • In the terminal try the key you just set (e.g F12) to see if it works. If it doesn’t work and in the case of F12 writes on the terminal a ~, close terminator and re-open it for the changes to get applied.

Second way to make terminator toggle its visibility using the F12 key (like guake)

  • Create the folder tree ~/.config/terminator (maybe it exists already). Please note that the . in front of config is purposely there, it is the way to hide a folder.
  • In the folder create a file named config (the full path would be ~/.config/terminator/config) and put the following as content:
[global_config]
[keybindings]
  hide_window = F12
[layouts]
  [[default]]
    [[[child1]]]
      parent = window0
      type = Terminal
    [[[window0]]]
      parent = ""
      type = Window
[plugins]
[profiles]
  [[default]]
  • Save the file and start terminator, pressing the F12 key should hide the terminal, pressing it once more should make it reappear.