Introduction to UNIX

1. Introduction to UNIX D. UNIX File Structure UNIX File System

2. UNIX File System Performance Objectives: 1. Identify types of Files (file) 2. Diagram the relationship of Files and Directories 3. Navigate the UNIX Directory Structure (cd, pwd) 4. Identify pathnames: Absolute (/) and Relative (. .. ~) 5. Define file naming conventions 6. Make and remove directories (mkdir, rmdir) 7. List files and directories and their attributes (ls) UNIX File System

3. Types of Files • Documents (ordinary files) • Directories (help organize other files) • Commands • Special files - pipe | • Hidden files (dot) • Devices UNIX File System

4. Relation of Files & Directories • Root is like a file cabinet. • A directory is like a file drawer • A subdirectory is like a folder within a drawer. • A path is a list of directories & subdirectories from root to a specific file or subdirectory. Root / Directories Files UNIX File System

5. UNIX Directory Structure • At login, you are in your home directory. • This is your current working directory. • All files and directories below your home directory usually belong to you. • You change your working directory by changing to another directory (cd). UNIX File System

6. Pathnames • Absolute Pathname: • shows the absolute position of a file or directory in the hierarchy; /home/user2/bif/docs • begins with a slash (/); and • describes how to get to the file from the root. UNIX File System

7. Pathnames • Relative Pathnames: • Describes how to get to a file from your current working directory. • Special characters represent directory locations. • home directory ~ ~chidhkra • current directory . cp ~chidhkra/file . • parent directory .. cp ~chidhkra/file .. UNIX File System

8. Filesystems • A file is identified by • Combining directory pathnames • To the filename /usr/local/meeting / root usr files local meeting UNIX File System

9. Naming Files • Filenames may be 1 to 255 characters • UPPER and lowercase, • numbers, • other ASCII characters, • except special Shell characters, control characters and the space. UNIX File System

10. Filename DON'TS • Don't begin a filename with a dot (.) • Don't use any of the following characters ; ? { } < : | * \ > # ( ) [ ] ' $ - & ~ " ! % / UNIX File System

11. Examples of UNIX File Names: status.memo casey_mt 1.2.3 chapter1 UNIX File System

12. Hidden Files (dot) • Used to establish your environment: .cshrc .login .pinerc .forward • Must use ls -a option to view • Always in home directory (some exceptions) UNIX File System

13. Programs like make, cc, and sccs use a default conventions to name files generated: <f>.o Binary Compiler Output <f>. i C preprocessor Output <f>.c C/C++ language source code <f>.f Fortran source code <f>.mk Makefiles s.<f> SCCS files a.out executable name <f>.j FPP output files <f>.a AR or BLD files <f>.Z compressed files (use uncompress) <f>.gz gzipped files (use gunzip) <f>.tar tape archive (use tar) <f>.l compiler listings Naming Conventions UNIX File System

14. Identifying File Content • The command file identifies file content: host% file passwd passwd: ascii text host% file ~dhk/* PSaddress: PostScript document acl: directory address: [nt]roff, tbl, or eqn input text adv.fil: ascii text cfs.size: executable shell script dip: shell commands UNIX File System

15. Directory Commands • mkdir making a directory • cd changing your working directory • pwd printing your working directory • ls listing the contents of a directory • rmdir removing a directory UNIX File System

16. Directory Commands - mkdir • Make directory under current working directory host% mkdir docs • Make directory under subdirectory host% mkdir docs/index • Make directory and subdirectory host% mkdir docs docs/index • Make directory using absolute path host% mkdir /usr/tmp/abc User1 (cwd) docs User1 (cwd) docs index UNIX File System

17. Common Error Messages: mkdir: dirname: File exists mkdir: dirname: Permission denied UNIX File System

18. Directory Commands - cd userx host% cd docs host% cd /usr/tmp/abc/docs host% cd ~abc/docs host% cd host% cd .. docs /usr tmp abc docs ~abc docs UNIX File System

19. Common Error Messages: • pathname: No such file or directory • pathname: Permission denied UNIX File System

20. Directory Commands - pwd • Determining the current working directory: host% pwd /scc/users/chitspit/bif • where: • / root • scc/ file system followed by the delimiter (/) • users/ subdirectory of scc • chitspit/ directory followed by the delimiter (/) • bif current working directory UNIX File System

21. Directory Commands - ls cwd host% ls bin mbox remodel complex.f outdis test host% ls -sF(Multiple options may be specified) 15 bin/ 256 mbox 3 remodel/ 34 complex.f 6 outdis@ 1 test* host% ls ~chitspit/bin au clst prod show xref UNIX File System

22. Directory Commands - ls • The long list provides additional file information: host% ls -l total 31 drwxr-xr-x 2 dhk 512 Oct 23 1985 bin -rw-r--r-- 1 dhk 129 Nov 20 1985 comp -rw------- 1 dhk 129 Jul 2 10:05 mbox -rw-r--r-- 1 dhk 4291 Jun 16 14:18 outdis drwxr-xr-x 2 dhk 512 Jan 22 11:07 remod -rwxr-xr-x 1 dhk 10291 Mar 19 12:55 test List alphabetized UNIX File System

23. List Hidden Files: ls -a • The -a option lists all files in a directory: host% ls -a . .login mail test .. bin public_html .cshrc complex.f remodel UNIX File System

24. Directory Commands - rmdir • The rmdir command removes directories. host% rmdir bif/docs • Directory must be empty. • Common error messages: • rmdir: docs: Directory not empty • rmdir: /scc/users/abc/docs: Permission denied userx bif docs UNIX File System

25. End of Module Complete UNIX File Structure Exercises UNIX File System