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					               Introduction to UNIX

                 D. UNIX File Structure




June 1, 1999            UNIX File System   1
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)




June 1, 1999                    UNIX File System                    2
Types of Files

•      Documents (ordinary files)
•      Directories (help organize other files)
•      Commands
•      Special files - pipe |
•      Hidden files (dot)
•      Devices

June 1, 1999           UNIX File System          3
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

June 1, 1999               UNIX File System                         4
 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).
June 1, 1999         UNIX File System         5
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.


June 1, 1999               UNIX File System                 6
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 ..

June 1, 1999               UNIX File System               7
Filesystems
• A file is identified by
          Combining directory pathnames
          To the filename            /usr/local/meeting
                            / root

                                             usr

          files                                    local

                                               meeting
June 1, 1999              UNIX File System                 8
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.



June 1, 1999               UNIX File System   9
Filename DON'TS
• Don't begin a filename with a dot (.)
• Don't use any of the following characters
           ;       ?   {}   <      :
           |       *    \   >      #
           () []       '    $       -
           &       ~   "    !      %
               /
June 1, 1999                UNIX File System   10
Examples of UNIX File Names:
      status.memo
      casey_mt
      1.2.3
      chapter1




June 1, 1999        UNIX File System   11
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)


June 1, 1999           UNIX File System   12
Naming Conventions
 •   Programs like make, cc, and sccs use a default
     conventions to name files generated:
       <f>.o Binary Compiler Output     <f>.j FPP output files
       <f>. i C preprocessor Output     <f>.a AR or BLD files
       <f>.c C/C++ language source code <f>.Z compressed files (use
       <f>.f Fortran source code               uncompress)
       <f>.mk Makefiles                 <f>.gz gzipped files (use gunzip)
       s.<f> SCCS files                 <f>.tar tape archive (use tar)
       a.out executable name            <f>.l compiler listings




June 1, 1999                   UNIX File System                       13
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

June 1, 1999                     UNIX File System             14
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



June 1, 1999           UNIX File System              15
Directory Commands - mkdir
• Make directory under current working
    directory
               host% mkdir docs                  User1 (cwd)

• Make directory under subdirectory                   docs

               host% mkdir docs/index            User1   (cwd)
• Make directory and subdirectory                   docs
               host% mkdir docs docs/index             index
• Make directory using absolute path
               host% mkdir /usr/tmp/abc
June 1, 1999                  UNIX File System            16
Common Error Messages:
mkdir: dirname: File exists
mkdir: dirname: Permission denied




June 1, 1999     UNIX File System   17
Directory Commands - cd
      host% cd docs                              userx

                                                         docs
      host% cd /usr/tmp/abc/docs /usr
                                            tmp
      host% cd ~abc/docs                         abc
                                                       docs
                                   ~abc
      host% cd
                                          docs
      host% cd ..
June 1, 1999           UNIX File System                         18
Common Error Messages:
• pathname: No such file or directory
• pathname: Permission denied




June 1, 1999      UNIX File System      19
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
June 1, 1999                      UNIX File System                  20
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


June 1, 1999                      UNIX File System                21
Directory Commands - ls
• The long list provides additional file
  information:                                            List alphabetized


          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

June 1, 1999                UNIX File System                          22
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




June 1, 1999                  UNIX File System     23
Directory Commands - rmdir
• The rmdir command removes directories.
               host% rmdir bif/docs                  userx

• Directory must be empty.                                   bif

                                                                   docs

• Common error messages:
                rmdir: docs: Directory not empty
                rmdir: /scc/users/abc/docs: Permission denied



June 1, 1999                    UNIX File System                      24
               End of Module
 Complete UNIX File Structure
   Exercises




June 1, 1999      UNIX File System   25

				
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