Introduction to Unix Editing with emacs Compiling with gcc

1. Introduction to Unix Editing with emacs Compiling with gcc

2. What is Unix? • UNIX is an operating system first developed in the 1960s • by operating system, we mean the suite of programs that make the computer work • There are many different versions of UNIX, although they share common similarities • the most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X • The UNIX operating system is made up of three parts: • the kernel, the shell and the programs

3. Files and Processes • Everything in UNIX is either a file or a process: • A process is an executing program identified by a unique process identifier • afile is a collection of data created by users using text editors, running compilers, etc. • All the files are grouped together in the directory structure • The file-system is arranged in a hierarchical structure, like an inverted tree

4. Tree Directory Structure root directory home directory current directory

5. Concepts • Root directory • Current directory • Home directory • Parent directory • Absolute path • Relative path

6. Tree Directory Structure Unix command: ls root directory Output: Sub a b c Unix command: ls /home/jane/data home directory current directory Output: Sub a b c Unix command: ls ~/data Output: Sub a b c

7. Tree Directory Structure Unix command: ls ~ root directory Output: data setup Unix command: ls .. home directory current directory Output: data setup Unix command: ls ./../.. Output: jim jane Unix command: ls ./../../jim Output: calendar

8. Tree Directory Structure Unix commands: cd ./../../../work ls root directory current directory Output: setups bkup home directory Unix command: ls ./.. Output: home work Unix command: ls / Output: home work Unix command: ls /home Output: jim jane

9. Tree Directory Structure Unix commands: ls ~/.. root directory current directory Output: jim jane Unix command: ls ~/../.. home directory Output: home work Unix command: ls setups Output: generic

10. Unix file security • Each file has owner and group • Permissions set by owner • Read, write, execute • Owner, group, other • Only owner, root can change permissions • This privilege cannot be delegated or shared

11. A Sample UNIX Directory Listing

12. Changing Access Rights • Use the command chmod For example, to remove read write and execute permissions on the file biglist for the group and others, type chmod go-rwxbiglist This will leave the owner’s permissions unaffected. To give read and write permissions on the file biglist to all, chmodo+rwbiglist

13. Basic Unix Commands (1) ls list files and directories ls -a list all files and directories cdname change to named directory cdchange to home directory cd ~ change to home directory cd .. change to parent directory mkdirnamemake a directory pwd display current directory path

14. Tree Directory Structure root directory Unix command: mkdir./bkup/zzz current directory Unix command: pwd home directory Output: /work zzz

15. Basic Unix Commands (2) cp file1 file2 make a copy of file1 into file2 cp -r dir1 dir2 make a copy of directory dir1 into dir2 mvfile1 file2 move or rename file1 to file2 rm file remove a file rm –r directory remove a directory catfile display a file less file display a file a page at a time who list users currently logged in * match any number of characters ? match one character man read online manual for a command

16. Unix command: cp ~/data/a . root directory current directory home directory zzz a

17. Unix command: cp–r /home/jim/calendar ./bkup/zzz root directory current directory home directory zzz a

18. Unix command: cp–r /home/jim/calendar/* ./bkup/zzz root directory current directory home directory zzz a

19. Unix command: rm–r /home/jim/calendar/* root directory current directory home directory zzz a

20. Unix command: rm–r /home/jim/calendar/* root directory current directory home directory zzz a

21. Unix command: mv ./bkup/zzz ./bkup/www root directory current directory home directory zzz www a

22. Basic Unix Commands (3) command > file redirect standard output to a file command >> file append standard output to a file command < file redirect standard input from a file grep keywordfile search a file for keywords wcfile count number of words in file sort sort data (numerically or alphabetically

23. Text editor EMACS

24. Text Editor emacs • Configurable, extensible text editor • To start emacs just “call it” emacs • Basic editing in emacs is somewhat intuitive • use arrows, “PG UP”and “PG DOWN”to move cursor • use DEL key to delete • typing inserts text at the cursor position • To edit an existing file type emacsfilename

25. Using emacs: keyboard commands • We use the following abreviations “C” is the “Control” key “-” between two letters mean both have to be pressed simultaneously • Basic commands C-x, C-s to save the file C-x, C-c to exit Emacs C-g to get out of trouble

26. Basic emacs Commands Cursor movement C-a (begin of line) C-e (end of line) C-v (page up) alt-v (page down) Save/Quit C-x C-c (quit w/out saving) C-x C-s (save) C-x C-w (write to a new file) Load file C-x C-f (delete line) Copy C-c Paste C-v Undo C-x u Delete C-k (delete line) Cancel C-g

27. Searching in Emacs • C-s : search for a string – this search is incremental and goes as you search – typing C-s again will search for the next occurrence of the same string – to go back to the editing, just press any arrow key – after you go back, typing C-s twice resumes the search

28. GCC Compiler

29. What is gcc? • Stands for GNU C/C++ Compiler • Popular console-based compiler for Unix platforms • Compile and link C programs: gccfilename.c output is an executable called a.out • Another option (we will be using this one): gccfilename.c–oxfilename output is an executable called xfilename • If you want to learn more, use the manual man gcc