Unix file system

1
Unix file system

• Home directory
• A directory set aside for your personal use
• The starting point when you log in
• Working directory
• Whatever directory you are currently in
• Initially, the working directory is the home
  directory
• The cd command is used to change the working
  directory

2
Typical Unix file system
root (/)
bin
dev
tmp
usr
var
users
classes
csfac
st
fac
staff
spool
mail
ugrad
ms
phd
cs201
801
(all users mail)
3
File and directory names

• Valid names can be made up of
• Uppercase letters (A to Z)
• Lower case letters (a to z)
• Numbers (0 to 9)
• period (.), underscore (_), commas (,)
• Should not contain spaces or the following
• \ lt gt ( ) ? / !
• You should also avoid naming files or directories
  with Unix commands

4
Absolute pathnames

• To use a file in Unix, all you need is its name
• To access a file in another directory, you need
  to know its pathname
• A pathname is an address that shows the files
  position in the file system
• Absolute path names give a files location in
  relation to the top of the file system structure
• The command pwd displays the absolute path of the
  current working directory

5
Example directory structure
root (/)
bin
etc
var
tmp
dev
home
usr
jill
jack
marsupials
Bats
continents
oceans
kangaroo
wombat
bandicoot
opossum
wombat
6
Absolute pathnames

• All absolute path names begin with a /
• Also called full path names
• Use the as a shortcut for the full path to your
  home directory

7
Relative path names

• Usually you are interested in a files location
  relative to where you currently are in the system
  
• A relative pathnames start at the working
  directory rather than the root
• Use .. to refer to the parent of the current
  directory

8
Example directory structure
root (/)
bin
etc
var
tmp
dev
home
usr
jill
jack
marsupials
Bats
continents
oceans
kangaroo
wombat
bandicoot
opossum
wombat
9
ls

• list
• Displays all files in the current working
  directory
• Flags
• -a shows all the files, including hidden ones
• -F puts a / after directories, an after
  executables, and an _at_ after links
• -l displays a long listing of files
• -R will also list contents of sub-directories
• -s will list the size of the files

10
Viewing the file

• What if you want to see the contents of a file?
• Use the cat command
• cat name of file
• cat snapshot06302005
• Use the more command
• more name of file
• more snapshot06302005

11
cp

• Copies the contents of one file to another
• cp file to copy new file name
• Flags
• -r will copy directories and all their contents
• Without this flag, the directory will not be
  copied and you will get an error message

12
mv

• Better name could be the rename command
• Changes the name of one file to another
• mv old file name new file name
• Note, if new file name is a directory, you will
  move old file name to that directory and keep
  the original name

13
rm

• remove
• Deletes the specified file or files
• This is destructive!
• They are gone!
• They cannot be retrieved!
• rm file name
• rm does not work with directories
• unless the r Flag is used

14
Creating files directories

• The command to create a directory is mkdir
• grid1 mkdir lab1
• To create a new text file, you can use pico or
  emacs
• You will learn more about text editors in lab