CS155: Unix and You Lecture 1

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CS155 Unix and YouLecture 1
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What is Unix?

• Unix is a multi-user operating system

user1 - Terminal
UNIX
user2 - remote
parsons.cs.colostate.edu 129.82.46.117
user3 - remote
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A Bit of History

• Unix was developed at Bell Labs in 1969
• Today, many incarnations of Unix exist
• Linux is a free and open source version of the
  Unix operating system.
• Most CS machines run Linux, but some machine run
  Solaris.

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What does it do?

• Unix is an interface to the resources of a
  computer
• Some of Unixs jobs include
• Interfacing w/ hardware CPU, memory, harddrives,
  peripherals
• Managing Processes program execution, memory
  allocation
• Handling Communication with other machines, with
  the user
• Resource allocation dividing processing time
  between the processes of users

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Logging In (and Out)

• Since Unix is multi-user, you must login to a
  machine to use it.
• ssh is a secure protocol for communication
  between computers
• ssh clients exist for Windows
• putty.exe a simple client
• SSH Secure Shell more advanced

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Logging In (and Out)

• What happens once Im in?
• A shell is opened
• A prompt is presented
• A shell helps you communicate with Unix
• The prompt allows you to give the OS commands

gt gt exit logout
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File System Basics

• The file system is a tree structure containing
  files
• Every file has a path that is its location
• e.g. /s/chopin/k/fac/boese/my_file

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Absolute and Relative Paths

• An absolute path is the path from the root
  directory, /
• A relative path is the path from the current
  directory
• . is a symbol for the current directory
• .. is a symbol for the parent directory

The absolute path to program is
/usr/local/bin/program If we were in /usr/bin the
relative path would be ../local/bin/program If we
were in /usr/local/bin it would be ./program
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Navigating the File System

• Navigating the file system is the first Unix
  skill you will learn
• Our first Unix commands pwd, ls, cd, more
• pwd print working directory
• ls list directory
• cd change directory
• more view a file

gt pwd /s/chopin/k/grad/nate gt cd /s gt pwd /s gt
ls bach chopin parsons preisner
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More Navigation

• Your home directory is where you are when you
  login to a unix system
• is a symbol for your home directory
• Options can modify behavior, for example

gt ls bach chopin parsons preisner gt ls
l total 8 drwxr-xr-x 3 root root 0 Jan 17
0302 bach drwxr-xr-x 4 root root 0 Jan 17
1544 chopin drwxr-xr-x 3 root root 0 Jan 17
1548 parsons drwxr-xr-x 3 root root 4096 May 27
2005 preisner
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The Structure of a Unix Command

• command option file
• Let us take ls as an example
• -l use a long listing format
• -S sort by file size
• -1 list one file per line

gt ls bach chopin parsons preisner gt ls
1 bach chopin parsons preisner gt ls chopin a k gt
ls l chopin total 8 drwxr-xr-x 5 root root 4096
Jan 17 0201 a drwxr-xr-x 5 root root 4096 Jan
17 0216 k