The Unix File sytem

Introduction

• Tree structure …

The on-line manual• man <command> gives detailed

information about UNIX commands and other facilities

• Details include command format, description, examples, known problems, related files and commands

• Sections for commands, programming, admin and others

• man intro for the introduction• man man (of course)

UNIX Filestore

• Files and directories

• The filesystem hierarchy

• File handling commands

Files• From the user’s point of view, all

information on the computer is stored in files

• Files may contain many kinds of information, including programs, data and documents

• Like paper files, they have a name (chosen by the user) and some content

• By convention, the filename suffix suggests the type of content

Example files

• Me.sh = Shell script• Me.pl = Perl script• Me.txt = Text file• Me.jpg, Me.png, Me.gif = Image files• Me.html = HTML web page file• Me.zip, Me.gz Me.bz2 = Compressed file• Me.tar = Archived file• Me.log = Log file

These are just conventions and are not enforced by the operating system!

Directories

• Files are stored in directories (folders in Windows)

• Each directory may contain many files and also other directories

• By convention, directory names do not usually have suffixes

The filestore

• There is a single hierarchical filestore that is shared by all users

• It might be spread over the network, may involve many disks on may different computers and may even be linked to other filestores

• Each user has their own personal home directory (~)

• There are also common areas for programs, administration, etc.

• The filestore starts at the root directory (/)

• A user is always in a current working directory (CWP) from which they give commands to access files

• When users log on, the CWP is set to their home directory

The filestore

(root)

staff usr bin stud etc

Research Teaching Private

pgugitmastersxxxgtrxxx

CUA

Coursework1.txt

CUA

xxx02u xxx04u

MVR

Lecture1.ppt

Lecture2.doc

.profile

The filestore

Where am I in the File Structure?

• pwd prints the pathname of the current working directory

• cd pathname changes current directory– with no argument it goes to the home

directory

Where am I in the File Structure? (2)

robin$ pwd/stud/ug/xxx04urobin$ cd USTrobin$ pwd/stud/ug/xxx04u/UST

robin$ pwd/stud/ug/xxx04u/USTrobin$ cd ..robin$ pwd/stud/ug/xxx04u/

(root)

staff usr bin stud etc

Research Teaching Private

pgugitmastersxxxgtrxxx

CUA

Coursework1.txt

UST

xxx02u xxx04u

MVR

Lecture1.ppt

Lecture2.doc

.profile

File handling commands – Viewing File Contents

• The cat [filename…] command displays the contents of the named files

• It reads the contents of the file(s) and outputs to the shell window

• with no arguments cat simply echoes back what you type at the keyboard

• there is no scrolling with the cat command

• more [filename…] lets you scroll through a file– also less [filename…]

Viewing File Contents (2)

• head displays the first 10 lines of a file

• tail displays the last 10 lines of a file

• ls [pathname…] lists the contents of the named directories– with no argument, the current directory is

listed• mv pathname1 pathname2 moves a file

from pathname1 to pathname2– if pathname2 already exists, then its

previous contents are lost– if not, then it is created

Viewing and Changing Directory Contents

• cp pathname1 pathname2 copies the contents of pathname1 to pathname2

– if pathname2 already exists, – then its previous contents are lost– if not, then it is created

• rm pathname removes files but not directories (be careful)

Viewing and Changing Directory Contents (2)

• mkdir pathname ... creates a new directory– it fails if they already exist

Manipulating Directories

robin$ rmdir fredrmdir: directory “fred”: Directory not empty

robin$ mkdir fredrobin$ mkdir fredmkdir: failed to make directory “fred”; File exists

• rmdir pathname removes directories– it fails if they are not empty