UNIX File Systems and Directories: A Comprehensive Guide, Study notes of Computer Science

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• COMP 4/6262: Programming UNIX Lecture 3 File systems January 25,

Outline {

UNIX file hierarchy

Working with directories

z current working directory, home directory z pathnames z list directory: ls (learn commands in general) z cd, mkdir, rmdir

Working with files

z list files z organize files: what goes where

UNIX filesystem {

The filesystem is your interface to

z physical storage (disks) on your machine z storage on other machines z output devices z etc.

Everything

in UNIX is a file (programs,

text, binaries, directories, peripheraldevices, terminals, …)

The file system provides a

logical

view of

the storage devices

UNIX file hierarchy

comp / usr bin home var lib classes students faculty comp 6262- 6262- 6262- 6262-

aquota.user

output.dat

Disk vs. Filesystem

The entire hierarchy can actuallyinclude many disk drives. z some directories can be on othercomputers / bin etc users tmp usr hollid scully

Working directory {

The current directory in which you areworking

pwd

command: prints the current working

directory

Unless you specify another directory,commands will assume you want tooperate on the working directory

Home directory {

A special place for each user to storepersonal files

When you log in, your working directorywill be set to your home directory

Your home directory is represented by thesymbol ~(tilde)

The home directory of 6262-00 isrepresented by

Special Directories {

current directory

parent directory

example

z if my current directory is my home directory z output.dat is equivalent to ./output.dat z .. is comp

These directories can be chained

z “../..” stands for two directories directly abovethe current directory /

usr

bin

home

lib

comp

classes

comp

Commands

in

general

synopsis: ls [options]… [dirNames]… { Options z [-abc]: any or all arguments within [] are optional z -a|-b : options delimited by | cannot be used together { Arguments z [expression]: entire expression within [] isrepeatable z argument … : argument is repeatable { You can mix any options with any dirNames { You can have multiple dirNames

Examples:

ls

{ ls { ls. { ls ~ { ls /home/classes { ls / { ls .. { ls -al /usr/bin { ls /usr/bin /tmp /etc { ls –l /usr /etc { ls /usr /bin -a

Creating and removing directories mkdir, rmdir {

mkdir

z

Makes a directory

z

mkdir myDir

{ rmdir

z

Removes an empty directory

z

rmdir myDir

File Contents {

Each file can hold some raw data

UNIX does not impose any structure onfiles

z files can hold any sequence of bytes

Many programs

interpret

the contents of

a file as having some special structure

z text file, sequence of integers, databaserecords, etc.

What Goes Where? {

/ z Root of the entire system z Comparable in Windows to C: (but you may haveD:, E: .. several roots) { /bin z Commonly used binaries (programs) { /sbin z More programs to run { /usr z User related commands as well as a whole bunch ofrandom stuff { /lib z Libraries go in here

And… {

/dev z All devices are located in here { /home z Traditionally, this is where user accounts are stored { /etc z Startup files and configuration files for daemons andother programs { /var z Various files go in here z Traditional location of mailboxes {

/var/spool/mail

/proc z Special files that contain information about thesystem or info from running programs