June 1, 1999UNIX File System1 Introduction to UNIX D. UNIX File Structure

June 1, 1999 UNIX File System 1

Introduction to UNIX

D. UNIX File Structure


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)


Types of Files

• Documents (ordinary files)

• Directories (help organize other files)

• Commands

• Special files - pipe |

• Hidden files (dot)

• Devices


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 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).


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.


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 ..


Filesystems

• A file is identified by Combining directory pathnames To the filename /usr/local/meeting

root

files

usr

local

meeting

/


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.


Filename DON'TS

• Don't begin a filename with a dot (.)

• Don't use any of the following characters ; ? { } < :

| * \ > #

( ) [ ] ' $ -

& ~ " ! %

/


Examples of UNIX File Names:

status.memo

casey_mt

1.2.3

chapter1


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)


Naming Conventions

• 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


Identifying File Content

• The command file identifies file content:host% file passwd

passwd: ascii text

host% file ~dhk/*PSaddress: PostScript documentacl: directoryaddress: [nt]roff, tbl, or eqn input textadv.fil: ascii textcfs.size: executable shell scriptdip: shell commands


Directory Commands

• mkdir making a directory

• cd changing your working directory

• pwd printing your working directory

• ls listing the contents of a directory

• rmdirremoving a directory


Directory Commands - mkdir• Make directory under current working

directoryhost% mkdir docs

• Make directory under subdirectoryhost% mkdir docs/index

• Make directory and subdirectory host% mkdir docs docs/index

• Make directory using absolute pathhost% mkdir /usr/tmp/abc

User1

docs

User1

docs

index

(cwd)

(cwd)


Common Error Messages:

mkdir: dirname: File exists

mkdir: dirname: Permission denied


Directory Commands - cd

host% cd docs

host% cd /usr/tmp/abc/docs

host% cd ~abc/docs

host% cd

host% cd ..

userx

docs

/usrtmp

abcdocs

~abc

docs


Common Error Messages:

• pathname: No such file or directory

• pathname: Permission denied


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


Directory Commands - ls

host% lsbin mbox remodelcomplex.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/binau clst prod show xref

cwd


Directory Commands - ls• The long list provides additional file

information:

host% ls -ltotal 31drwxr-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 outdisdrwxr-xr-x 2 dhk 512 Jan 22 11:07 remod-rwxr-xr-x 1 dhk 10291 Mar 19 12:55 test

List alphabetized


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


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


End of Module

Complete UNIX File Structure

Exercises