Week 4, Intro to Unix lab 2016

Content

• Homework discussions - rights
  • limit number of arguments. Try ls /*/*/*/*
• Recapitulation
  • numeric representation
  • permissions 000, 600, 700, 644, 755 what is the behaviour?
  • Show the names and login times of the currently logged in users
  • Quick recap test - show prikazy.txt
• env, standard variables, calling script from anywhere and PATH variable
• mail: mail me (email on white board) and yourself in carbon copy (cc) your login and your machine name so I can see where you are sitting
  • use one liner
• write a pomodoro script which email to stretch every 20 minutes
• last, sort, join, uniq, /ect/passwd # or getent passwd
• if time, prepare for future:
  • find - look at the syntax till next time
    • print is not like printing - 1200 pages cost money
  • recap less, more, pg
  • sync

Homework

Send me both your scripts but also the files counts_days and days_counts

• (2 points) Count number of logins to machine u-pl24 per day of week
  • hints:
    • last, sort, uniq
    • ssh YOUR_NAME@u-pl24.ms.mff.cuni.cz
  • Store the results to counts_days file in format:

  243 Mon
  992 Tue
  823 Wed
 1202 Thu
  602 Fri
  123 Sat
   32 Sun

• (1 point) Swap the columns from counts_days
  • Keep the numbers aligned to the right side
  • Store the results to days_counts file in format:
  • Hints: cut, paste character positions

Mon  243
Tue  992
Wed  823
Thu 1202
Fri  602
Sat  123
Sun   32

Bonus

• (0 points) Write your homework using vim
  • Finish vimtutor tutorial before starting
• (1 point) Change homework from third week so you backup dotfiles and dotdirectories and change the directories permissions recursively and files recursively so you cannot change/delete them.
• (1 point) How many users with first name Jan can login to Rotunda lab?
  • Submit the code and write me a number into the email
• (1 point) Similarly to homework count number of logins to u-pl24 per first name of user
  • Hints:
    • join command
    • Do not use /etc/passwd but getent passwd in Rotunda lab
  • Send me also the output in first_names.txt file
• (2 points) - Draw a histogram for days_counts file:
  • Suppose that the first two columns do not exceed 18 characters
  • Distribute 60 ‘=’ characters proportionally according counts
  • See example of desired output for only three days.
  • Send me also the output in histogram.txt file
  • See example output for data Mon 1, Tue 40, Wed 80

Mon  1 =
Tue 40 ====================
Wed 80 =======================================