UNIX

Beginnings of Unix

After being withdrawn from project Multics Ken Thompson and Dennis Richie started writing UNIX in 1969 at AT&T Bell Labs.

Ken Thompson and Dennis Richie found themselves at the Bell Labs without much hardware or funding.

Having to resort to discarded hardware and influenced by their experience of Multics, they start developing UNIX, a super slim operating system, that could run in hardware available and yet include some of appealing features of Multics.

Features of UNIX

Some of the features of UNIX were influenced from Multics,

• it was time-sharing system, allowing for mutiples users to login to the machine ssh username@machineIP
• included the shell: a program which performs command line interpretation whoaim pwd (print working directory - where am I) date users
• tree-structured file system
  • tree ~/ list contents of home (~ == /home/username ) in a tree-like format
  • ls ~ list files and directories in your user home ( ~ == /home/username )
  • ls . list files and directories in current directory ( . == current dir )
  • ls ../ list files and directories in parent directory ( . == current dir )
  • ls foo/ list files and directories in child foo/ directory
  • ls / list files and directories in root ( / == root )

Others emerged from the development and use of the system and crystallized into the Unix Philosophy:

• Write programs that do one thing and one thing well ls lists files in a directory cat outputs content of file wc counts number of words in file
• Write programs that work together
  • echo "hello UNIX world"|sed 's/o/0/g'|sed 's/e/3/g'| sed 's/l/1/g'|figlet
• Write programs that handle text streams, because that is a universal interface
  • man -a intro | espeak Linux introduction to user commands.

man pages

every thing is a file

Distribution of UNIX

Forking of UNIX

• Linux distributions
  • package managers: aptitude

• Mac OsX
  • homebrew http://brew.sh/