Basic Unix Commands

1. Basic Unix Commands CGS 3460, Lecture 6 Jan 23, 2006 Zhen Yang

2. For this class you need to work from your grove account to finish your homework • Knowing basic UNIX commands is essential to finish your homework

3. Overview • Files and Directories • How to connect to GROVE • Basic UNIX commands • TAR • Permissions • UNIX editor pico • Compiling C programs

4. Files and Directories • In computers, what is the difference between a file and a directory? • A file is a program or a document • A directory contains files or other directories

5. Directory Structure • Inside directories, you could find files and other directories • Inside those “other” directories, you might find more files, and more directories

6. How do I connect to grove? telnet grove.ufl.edu

7. Telnet Window • For login, enter the username on your grove account card • For Password, enter the password on the grove account card • Grove will ask you to change your password • Just follow the on-screen instructions • http://grove.ufl.edu/ for more information

8. UNIX Commands • mkdir [directory]– create a new directory • ls–list files or directories in current directory. • ls –l list in long format (including details like permissions, owner, size, etc.)

9. More UNIX Commands • pwd–let you know the absolute pathname of your current working directory (Where your are) • cd [dir]– changedirectory • cd ..–go back to parent directory. “..” is the relative pathname to the parent directory.

10. More UNIX Commands • pico [filename]: createa new file • Text editor • ^X to quit and save the file • cp • cp [file1 file2]– copy file1 to file2. If there’s already a file2, the old one will be overwritten.

11. More UNIX Commands • mv [sourcefiletargetfile]–basically mv renames sourcefile to targetfile. If there’s a file with the same name as targetfile, it will be overwritten. • rm file(s)– delete file(s). • rmdir directories–delete one or more empty directories.

12. TAR • Create tape archives and add or extract files. • Creating a tar file: tar -cvf file.tar myfile.txt In the above example the system would create a tar named file.tar in the directory you currently are in. tar -cvf file.tar *.txt would compress all txt files in the current directory. tar -cvf home.tar home/ In the above example command the system would create a tar file named home.tar in the directory you currently are in of the home directory.

13. TAR • Extracting the files from a tar file: tar -xvf myfile.tar In the above example command the system would uncompress (untar) the myfile.tar file in the current directory. tar -xvzf myfile.tar.gz In the above example command the system would uncompress (untar) the myfile.tar.gz file in the current directory. Note: There is no "untar" unix command.

14. Permissions • There are three types of file access supported by UNIX. • r– read, view the contents of a file • w–write, edit file/directory contents • x–execute, run executable file

15. - rwxr-xr-- 1 c3460abccgs3460 858 Jan 23 8:28 f1 owner links type size Modification date/time File name group User permissions Group permissions Other Permissions

16. Permissions • read=4;write= 2;execute=1 • rwx r-x r-- 4 + 2 + 1 4 + 0 + 1 4 + 0 + 0 7 5 4

17. Permissions • chmod mode file(or directory) –change the permission of the file or directory. • Examples: • Change the permission of file2 to: • rwx r-x --x • chmod 751 file2 .

18. Unix Editor pico • Simple and very easy to use text editor on UNIX • Open a file using pico pico filename For example: pico hello.c The above example would open the editor with the file hello.c if present. • Basic pico command (^ hold ctrl key) ^W where is ^Y previous page ^V next page

19. Compiling C Programs gcc is the "GNU" C Compiler. It is a free compiler that is available on grove.ufl.edu. Below are several examples that show how to use gcc to compile C programs.

20. Compiling a simple program • Consider the following example: Let "hello.c" be a file that contains the following C code. #include <stdio.h> main() { (void) printf("Hello…\n"); return (0); } • A standard way to compile this program is with the command gcc hello.c -o hello This command compiles hello.c into an executable program named "hello" that you run by typing './hello' (or possibly just 'hello') at the command line. It does nothing more than print "Hello..." on the screen.

21. Compiling a simple program • Alternatively, the above program could be compiled using the following two commands. gcc -c hello.c gcc hello.o -o hello The end result is the same, but this two-step method first compiles hello.c into a machine code file named "hello.o" and then links hello.o with some system libraries to produce the final program "hello". In fact the first method also does this two-stage process of compiling and linking, but the stages are done transparently, and the intermediate file "hello.o" is deleted in the process.

22. Compiling a program with multiple source files • If the source code is in several files, say "file1.c" and "file2.c", then they can be compiled into an executable program named "myprog" using the following command: gcc file1.c file2.c -o myprog The same result can be achieved using the following three commands: gcc -c file1.c gcc -c file2.c gcc file1.o file2.o -o myprog