Linux Workshop Session 1

1. Linux WorkshopSession 1 Khadka, Santosh and Panthi, Sanjeeb Computer Science Department Lamar University

2. What is covered? • Working with files • Working with directories • Some basic commands • Process related commands • Working with vi editor • Brief Introduction to Nano Editor

3. Login! Galaxy Account can be used to access all the Linux machines in the lab 208, both locally and remotely • To access locally, go to the any machines in 208 and use your username and password to login. • To access remotely, use any secure shell (ssh) software. Example puTTY . • Open a terminal by right clicking on your desktop. • Type pwd -> shows the current working directory. You are in your home directory.

4. Tools Required for Remote Access • ssh client - Example: putty for Windows platform • sftp client - Example: WinScp for Windows platform • remote sftp compatible editor - Example: jEdit for platform that supports java

5. Working with files • To list all the files and/or folders in a current directory by default. • ls [option]… [file]… • Options: • -a: to list all files • -l: to list in long format showing file attributes and permission • --author : gives the author name of the files. Better use with the combination of –l. • File: Default is current working directory.

6. Working with files • vi <filename> -opens a file to edit if exist, otherwise creates new file to edit • ls - lists contents in current directory • ls /etc - lists contents in directory /etc • ls -a - this will list all file including those beginning with the'.' that would normally be hidden from view. • Output redirection - Copies the output to some other file. Example: ls –l > filename (overwritten)‏ ls –l >> filename (appended)‏

7. Working with files • ls -l - this gives a long listing showing file attributes and file permissions. drwxrwxr-x 6 santoshksantoshk 4096 Sep 14 11:39 test -rw-rw-r-- 1 santoshksantoshk 140 Nov 17 09:08 test1.c • cat <filename> - displays the content of the file - example: cat filename - cat –n filename (-n option for giving the line number)d • cp <sourcefile> <destinationfile> - copy the content of the file - example: cp sourcefile.txt destnationfile.txt (source file is not deleted/modified)‏

8. Working with files • script - to make script file - records everything printed on your screen. The record is recorded to the filename specified. - starts scripting, once done, type in <ctrl>+d to end scripting Example: script filename - makes a script file with the given filename script -a filename - append the session record to filename, rather than overwrite it • mv <sourcefile> <destinationfile> - example: mv sourcefile.txt destiantionfile.txt (the sourcefile file is deleted)‏

9. Working with files • tar - create archives and add or extract files • tar –cvf output.tar inputfile • Example: tar –cvf aos.tar AOS • restore a tar file • tar -xvf inputfile.tar • .tar file is not compressed by itself. It just bundles the list of files in one folder. • add -z option to create a compressed tar file Example: tar -cvzf file.tar.gz

10. Working with files .gzip – compress the files Example gzip <filename> .gunzip –decompress the file Example gunzip <filename.gz>

11. Working with files • wc - counts the number of lines,words and bytes in the file - example: wc –l filename • head - outputs the first part of the file - prints the first 10 lines by default - example: head filename head -n count filename • tail  - outputs the last part of the file. - example: tail mylist.cpp

12. Working with files • lpr - print command - command: lpr -p printername filename Example: lpr -p lab208Printer -#2 file1.txt file2.txt (this will print two copies of file1.txt and file2.txt)‏ Note: This is not available at present.

13. Working with directories • cd - changes the directory - example: cd <foldername> • mkdir - creates a directory under the current working directory. - example: mkdir <foldername> • rmdir - remove files - example: rmdir <directoryname> (for empty directory)‏ rmdir –rf directoryname (recursive deletion with force)‏

14. Working with files contd.. • Absolute path: start with / (root) to go specific directory regardless of where you are now. • Relative path : start with the current directory to go specific directory. • Example: • If, pwd: /home/myfolder then to go /home/myfolder/c++ • Absolute path : cd /home/myfolder/c++ • Relative path : cd c++

15. A few basic commands • man - help manual - example: man keyword - press <Space bar> to view the next page - press <return> to view next line - type “q” exit • date - display or change the date - example: date --date =‘2 days ago’ date --set=“2009-9-4 11:59” date '+DATE: %m/%d/%y%n TIME:%H:%M:%S' DATE: 02/08/01 TIME:16:44:55

16. A few basic commands • chmod - used to change the access permission - used to set file permissions to owner, group, and other -rw-rw-r-- 1 santoshksantoshk 140 Nov 17 09:08 test1.c - r = 4, w = 2, x = 1 - example: chmod 444 mylist • clear - clear the screen • grep- search the file for the specific text - example: grep string filname

17. A few basic commands • hostname - displays or set the system name - example: hostname [name] - with no arguments prints the current host name. - with arguments sets the current host name to the specified string. • more - display output one screen at a time - related command: less • quota - display disk usage and limits - related command: du, df du –estimate the file space uses df – disk space uses (amount of disk space available)

18. Process related commands • ps- gives information about the running processes - example: ps -ef ps -fu username • kill - sends a signal to a process to kill (ends the running process) - example: kill -9 pid • exit - exit from the shell. If there are suspended jobs one cannot exit from the shell , so kill the processes using the kill command.

19. Brief Introduction to vi Editor • vifilename • esc - to enter vi command mode • h: moves the cursor one character left (l right) • j :moves the cursor one character down (k up) • u :undo the last changes in the file • x :deletes the character under the cursor • d^: deletes all the characters from current cursor to beginning of the line • d$ :deletes all the characters from current cursor to end of the line • dw: deletes one word from the cursor.

20. Brief Introduction to vi Editor contd.. • Insert text Enter input mode and: i a - insert text before ('i') or after ('a') the current character I A - insert text at beginning ('I') or end ('A') of current line o O - open new blank line after ('o') or before ('O') current line r R - replace one(‘r’) or more character (‘R’) by overwriting

21. Brief Introduction to vi Editor • Exiting and Saving - Press esc and type :q to quit :wq or ZZ to save and quit :q! to quit without saving (!= Forcefully) :w to save the file :w filename to save current file under name filename • Copy and Paste text nyy or nY - 'copies' n number of line p P - insert the contents of the paste buffer [ after / before ] the current line/character.

22. Brief Introduction to vi Editor • Delete text x X - Delete current ('x') or previous ('X') character dw - Delete the current word dd - Delete the current line D - Delete the rest of the line 5dd - Delete the next five lines 37Gdd - Delete line 37 J - Join lines • Undo u - Undo most recent change to the file

23. Brief Introduction to vi Editor • Global Searching and replace: /text - Search forward for some <text> ?text - Search backward for some <text> n - Repeat the previous search for the 'next' occurrence N - Repeat the previous search but in the opposite direction ' ' (two single quotes) - Go back to where you where previously :1,$s/oldtext/newtext/g - global substitutions

24. Brief Introduction to vi Editor • Other popular commands ^ - go to start of line $ - go to end of line :1 - goes to top of file :5 - goes to fifth line of file :$ - goes to bottom of file :set nu - will number all your lines :set nonu - turn off line numbering • Ctrl-g - show line number of current line

25. Brief Introduction to Nano Editor • To edit a file called filename, type nano filename. • cntrl g - (^G) with display a Help file with a bunch of information about using nano. • cntrl o - (^O) or (f3) will write or save the file • cntrl x - (^X) will exit the program and return you to the prompt • cntrl d - (^D) delete character currently under the cursor • cntrl k - (^K) delete entire line • cntrl u - (^U) paste text • ^\ - search for (and replace) a string of characters • BackSpace delete character currently in front of the cursor

26. Compiling files in linux • C++ file g++ [options] source_file –o outputfile g++ myfile.cpp g++ -Wall myfile.cpp -ooutputfile • C file gcc [options] source_file –o outputfile gccmyfile.c • java file javacMyfile.java java Myfile

27. Debuggin c/c++ file • gdb outputfile • To set the break • (gdb) break filename:line number • (gdb) functionname • To remove the break • (gdb) clear function /line number • To run • (gdb) r • (gdb) step (each step) • (gdb) next [count] // how many line

28. Debuggin c/c++ file • To watch the variables • (gdb) watch variablename • (gdb) watch expression • To quit • (gdb) q

29. Thank You !!!