Research

What exit status the command read generates? Try it

• Important: Please consult help read (e. g. here) command instead of man read, because read is shell built-in and you got manual page on all shell builtins

Research

How to suppress «\n» output after echo (see echo)?

Task

Write a c8 script that asks user for name, and prints a welcome message either if an user has entered a name or not:

   1 $ ./c8
   2 Enter your name: Spot
   3 Hello, Spot!
   4 $ ./c8
   5 Enter your name: 
   6 Hello, tmpuser?
   7 

• Hint: In second example user had not pressed «Enter»

• Create 01_UsingVirtualbox on sugon server

• Run VM
• Open terminal inside vm

• Enter command ip link show dev eth0

• Create 01_UsingVirtualbox/mac file containing the output of your VM's ip link command

  • Copy+paste may work

  • scp also may work

• Make a vitrualbox snapshot of the installed system

TODO

• Complete all tasks

• expr again

• Write a shell script sumsum.sh that

  • Has function sum() that

    • sums all of it's arguments (any number of arguments are permitted)
    • prints this sum if there's no errors

    • prints 0 if there was error (e. g. try to sum non-numbers)

    • redirects all error messages to /dev/null

  • Reads two lines of numbers
  • Prints if their sums was equal or not

       1 $ ./sumsum.sh
       2 1 3 5
       3 2 4 6
       4 Not equal
       5 $ ./sumsum.sh
       6 1 5 6
       7 4 4 4
       8 Equal
       9 $ ./sumsum.sh
      10 1 2 w
      11 3 4 e
      12 Equal
      13 $ ./sumsum.sh
      14 1 2 1
      15 2 2 Q
      16 Not equal
      17 $ ./sumsum.sh
      18 qwe 3 4
      19 10 20 -30
      20 Equal
      21 
    

Create 04_VirtualBox2 folder on sugon server. All files should reside there.

1. Save the contents of the /proc/cmdline file to the cmdline file

2. Save the output of the systemctl status sshd command to sshd-status file

3. Copy the /etc/group and /etc/passwd files

To copy files to a folder on a remote server, use the scp command:

$ scp /path/to/local/file username@hostname:/path/to/remote/file

$ scp username1@hostname1:/path/to/file username2@hostname2:/path/to/other/file

For example:

$ scp -P 2131 /etc/passwd andrey@sugon:/home/andrey/04_VirtualBox2/

Complete all tasks. Pay your attention at last tasks (check if the system has virtualbox-addition-guest module and install it, if it doesn't).

Create 05_Packages directory on sugon server.

• Install the sos package in VM

• Run sosreport binary from root. It will create system info file.

• Scp the file it had created to the 05_Packages directory on sugon server.

0. Create 06_Services catalog on sugon server. All files should reside there.

1. Finish all the tasks.
2. Save information on the status of the services to text files.

   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ systemctl status srv.mount > srv
   
   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ systemctl status echosrv.service > echosrv

3. Upload the files to the 'sugon' server. To copy files to a folder on a remote server, use the 'scp' command:

   scp /path/to/local/file username@hostname:/path/to/remote/file
   
   scp username1@hostname1:/path/to/file username2@hostname2:/path/to/other/file

   For example:

   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ scp -P 2131 srv andrey@sugon:/home/andrey/06_Services
   andrey@sugon's password:
   srv                         100%  472    80.8KB/s   00:00
   
   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ scp -P 2131 echosrv andrey@sugon:/home/andrey/06_Services
   andrey@sugon's password:
   echosrv                    100%  447    71.1KB/s   00:00

   Note: I do not publish here 'sugon' IP. Please insert the valid IP yourself.

Get ready for testing!

…

Finish all the tasks:

0. Look at the last task: there's system programming here

1. Create folder 09_Services2 at sugon.

2. Put there the updated tcp_echo_serverSR.c file.

3. Save systemd journal with events related to the services into text files and upload them to sugon. Hexdump service:

   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ journalctl -u hexdump*service > hexdump.journal

   TCP echo service:

   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ journalctl -u echosrv.service > echosrv.journal

Create 10_Network directory on sugon server

0. Finish all tasks.
1. Write two shell scripts:

   • base.sh — sets up internal network on base (just 3-4 commands above)

     • ip link set… — maybe

     • ip address add …

     • sysctl …

     • iptables …

   • clone.sh — sets up internal network on clone (just 3-4 commands)

     • ip link set… — maybe

     • ip address add …

     • ip route add …

     • /etc/resolv.conf will be overwritten, so you need to add something like echo nameserver 1.1.1.1 > /etc/resolv.conf to your script

2. reboot both VMs

   • run base.sh on base

   • run clone.sh on clone

   • check if host ya.ru is working on clone (that means network is working)

3. Scp 4 files on sugon server in 10_Network directory:

   • base.sh

   • base.log — the output of ip a command on base

   • clone.sh

   • clone.log — the output of ip a command on clone

1. Log in to sugon and create a folder named 11_ApplicationBus.

2. Finish all the tasks on VE
3. Listen to D-bus messages with 'dbus-monitor'. In the first terminal, run 'dbus-monitor' to listen to messages:

   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ dbus-monitor | grep -A 10 -B 4 "Hello world"

   In the second terminal, send a notification:

   andrewt@comp-core-i7-3615qm-0dbf32 ~ $ notify-send "Hello world"

   Save what was recorded by 'dbus-monitor' to the 'notification.log' file and upload it to 'sugon'.
4. Listen to D-bus messages with 'dbus-monitor' to know the call that changes wallpaper.
   • Run 'dbus-monitor':

     andrewt@comp-core-i7-3615qm-0dbf32 ~ $ dbus-monitor | grep -A 10 -B 10 "last-image"

   • Change the desktop wallpaper.
   • Find the method call that changes wallpaper in the 'dbus-monitor' output.
   • Based on the call description from 'dbus-monitor' write a command that changes the wallpaper using 'qdbus'. Hint: andrewt@comp-core-i7-3615qm-0dbf32 ~ $ qdbus org.xfce.Xfconf bla-bla-bla
   • Save the command to the 'wallpaper.sh' file and upload it to sugon.

5. Modify the server.py service. Add a new method: Signature:

   <method name='MultiString'>
               <arg type='s' name='a' direction='in'/>
        <arg type='u' name='num' direction='in'/>
        <arg type='as' name='response' direction='out'/>
   </method>

   Body:

   • def MultiString(self, s, num):
         """returns n strings"""
         return s * num

   Call this method from 'dbus-send' (specify types of arguments as: string and uint32).

6. Save the program itself and the output (to the 'miltistring.log') and save it to sugon.

Finish all unfinished programs. Create the 12_HighLevelLanguages folder at the sugon server. Put all programs there.

Home tasks

• Task 03

• Task 04

• Task 05

• Task 06

• Task 07

Bonus task

Bonus task (if done) should reside in 13_Bonus subdirectory on sugon server. Put there all the files related to your solution, including the prigram itself and 1-million digits pi file it used.

0. Preliminaries:

   • Take look on Chudnovsky Pi calculation algorithm.

     • $$ \frac{(640320)^{3/2}}{12\pi}=\frac{426880\sqrt{10005}}{\pi} = \sum_{k=0}^{\infty} \frac{(6k)! (545140134k + 13591409)}{(3k)!(k!)^3 (-262537412640768000)^{k}} $$

   • Learn Python decimal data type.

     • How to control precision with getcontext().prec = precision (see example at the very start of documentation)

   • Donwload 1-million precise $$\pi$$ representation (e. g. form here)

     • Remove all non-numeric characters from it
     • Actually we need no more than 40000 digits for ordinary CPU

   • (still no bonus ☺) Write a python program PiChud.py N that iterates over Chudnovsky formula N times and prints out how many exact digits from real $$\pi$$ it has calculated:

     • george@inspiron:~/src> python3 PiChud.py 4
       57
       george@inspiron:~/src> python3 PiChud.py 40
       568
       george@inspiron:~/src> python3 PiChud.py 400
       5674

       • This program calculated 75, 568 and 5674 exact $$\pi$$ digits on 4, 40 and 400 iterations of Chudnovsky formula respectively. Your results and time may differ.

       • Use 40000 digits Decimal precision

       • Make sure you're useng only integers and Decimals and no floats

1. (bonus) Use miultiprocessing to speed up calculations about N times, when N is the number of cores on your computer. Call the resulting program PiChudP.py

   • N can be actually lesser than number of cores. E. g. on 12-core CPU under Linux:

     george@inspiron:~/src> time python3 PiChud.py 800
     11347
     python3 PiChud.py 800  19,94s user 0,01s system 99% cpu 19,952 total
     george@inspiron:~/src> time python3 PiChudP.py 800
     11347
     python3 PiChudP.py 800  24,00s user 0,11s system 1002% cpu 2,406 total

     • Parallel version took more userspace CPU time than single-process (24.00s over 19.94s)

     • Parallel version worked 8 times faster than single-process (2.406s over 19.952s)

2. (more bonuses). Rewrite the program (call it PiChudPA.py) to work N seconds exactly and then stop calculating. Print digits per CPU core statistic (use os.cpu_count()):

   george@inspiron:~/src> python3 PiChudPA.py 60
   33626 digits, 2802.17 per core

Teaser: this is my solution of bonus task № 2. Note you probably will finish with slightly lager code