Week 2, Intro to Unix lab 2016

Content

• Thanks for PR (pull requests)
  • Keep contributing! Not only spelling fixes but also your suggestions and interesting literature are very welcome!
• Homework recap
  • Instructions, intentions, problems and scoring
  • parameters man -S1 man and man -S 1 man
  • Comments # this is a comment - it does nothing
  • Debugging set +x, set -x - Try it at home! What does it do?
  • copying out scripts from lab scp, using ssh -Y, or winscp
• tr presentation by Hlupaco
• Basic commands: touch, echo, cp, mv, rm, mkdir,
  • relative paths ., .., ../..
  • links (with relative paths and pitfalls) ., ln -s
  • important standard paths: /bin, /var, /etc, /usr, ...
• cd, cd -, cd /path/to/directory, cd .. # go to parent directory, cd ../.. # go two directories up
• man and less. Navigation (j, k, Ctrl+k, Ctrl+p, /, q)
  • apropos and man -k
  • --help parameter
• pipes, stdin, stdout
  • redirecting file to stdin
    • by cat my_file | head -n 2
    • by head -n 2 < my_file
    • Do not confuse with using the file name as argument!
      • head -n 2 my_file
  • redirecting to file, e.g. cat my_file.txt > copy_of_the_file.txt
  • redirecting error output to file ls -l not_existing_file.txt 2> error > attribute_of_file.txt
  • swapping stderr and stdout
    • useful e.g for pipes ls -a not_existing_file.txt 2>&1 > attribute_of_file.txt | tee error
    • useful for printing to stderr echo "printing to stderr" 1>&2"
• script arguments

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# content of script test.sh

# printing help to stderr
echo "Usage: $0 [arg1 ...]" 1>&2
echo All arguments
echo $@

for arg in $@; do
    echo $arg
done

echo First argument
echo $1

• next time
  • chmod, chown and ls
  • Intro to vi and vim

Homework

(3 points) Imagine you have three files text, table1, table2.

• The file text contains free text.
• The file table1 contains sequence of characters which should be replaced from the file text on single row.
• The file table2 contains sequence of characters which should be replaced to based on the file text and the sequence in file table1 on single row.
• Note: Strange characters like ’*’, new line (LF), ‘?’ or space may appear in all three files.
• The result save into file results.

Bonus

• (2 points) Prepare a short presentation (in Czech) about cut command
  • Explain to others how it can be used
    • Syntax and how to read the manual page
    • Use with echo and pipes (Pipes will be introduced next time).
    • Prepare at least three examples how it can be used. Use standard files such as /etc/passwd
• (2 points) Man - time exercise from first week
• (Easy Vim understanding) Go through Vimtutorl by running vimtutor from shell