Lecture 5: File Systems ( ch 4)

1. Lecture 5: File Systems (ch 4) IT244 - Introduction to Linux / Unix Instructor: Bo Sheng

2. Outline • Filename and paths • Directory operations • Access permissions

3. Filenames and Paths • Absolute path name • ls /home/it244/it244 • ls /home/it244/it244/ /home/it244/it244/hello Path Filename

4. Filenames and Paths • Absolute path name

5. Filenames and Paths • Absolute path name • ~ represents “home directory” • ls ~ =ls /home/your username • cd ~ • pwd • ls ~it244 =ls /home/it244

6. Filenames and Paths • Relative path name • cd /home/it244 • ls it244 /home/it244/it244/hello Path Filename

7. Filenames and Paths • Relative path name • . : Current directory • .. :Parent directory • ls –la • ls . • ls .. • cd .. • cd ../..

8. Filenames and Paths • Relative path name

9. Filenames and Paths • Standard directories (Pg95~98)

10. Directory Operations • Create a directory • mkdir book • ls -l • ls book • ls ./book • cd book • ls ../book

11. Directory Operations • Delete a directory (when it’s empty) • cd .. • rmdir book • Example • mkdir book • cd book • echo “this is a book” > book1 • cd .. • rmdir book (not empty)

12. Directory Operations • Example • rm book/book1 • rmdir book • Delete directories by rm • mkdir book • rm book • rm –r book (cautious)

13. Directory Operations • Example • mkdir book • cd book • mkdir novel • cd .. • rmdir book • cd book/novel • rmdir .

14. Directory Operations • Copy and move files to directories • cd ../.. • cp hello book • ls book • mv welcome linux book • ls • ls book

15. Directory Operations • Copy and move files to directories • mv book newbook • mv newbook book • ls • mkdirnewbook • mv book newbook

16. Directory Operations • Copy and move files to directories • mv newbook/book book • cp book newbook ??? • cp –r book newbook • lsnewbook

17. Access Permissions • Three types of users • Owner • Group member • Others • Three access permissions • Read • Write • Execute

18. Access Permissions

19. Access Permissions • Change access permissions (chmod) • Symbolic arguments • a (all), u (owner), g (group), o (others) • r (read), w (write), x (execute) • + / - • chmoda+w book1 • chmod go-rw book1

20. Access Permissions • Change access permissions (chmod) • Numeric arguments -rw-r--r-- 644 -rwxr-xr-x 755

21. Access Permissions • Change access permissions (chmod) • Numeric arguments • chmod 644 book1 • chmod 755 book1

22. Access Permissions • Example • Read permission • chmod a-r hello • cat hello • chmoda+r hello • cat hello

23. Access Permissions • Example • Read permission • chmod a-r book • ls book • ls book/book1 • chmoda+r book

24. Access Permissions • Example • Write permission • chmod a-w hello • echo hi>hello • rm hello • chmoda+w hello • rm hello

25. Access Permissions • Example • Write permission • cd book • chmod a-w . • chmoda+rw book1 • echo hi>book2 (create a file) • mv book1 book2 (rename a file) • rm book1 (delete a file) • chmoda+w .

26. Access Permissions • Example • Execute permission (directory) • Determine if the files are searchable • chmod a-x book • ls book • ls book/book1 • cd book • chmoda+x book Why?