The Shell

• Shell - user interface to Operating System (OS)
• User can use shell to run programs to perform tasks like manipulating files, performing calculations, etc.
• Graphical shells are more popular - controls such as menus/buttons to manipulate with mouse
• Alternative to graphical shell is command-line shell - user can type in commands to perform actions
  • often faster for developers to use command line shell

The Linux Shell

• Linux - freely-distributable Unix-like OS
• Some old Unix shells include:
  • C shell (csh)
  • KornShell(ksh)
  • Bourne-Again Shell (bash)
  • Tcsh, Zsh, fish
• echo $0 - gives type of shell you are running, e.g. /bin/bash
• bash --version - gives version of bash

Linux Filesystem

• Operating systems must have a way to organize info stored on machine
• Smallest entity where info is stored is a file
• Some files are special in that they contain the name of other files/references to them - these are called directories in Unix (vs. Folders in Windows)
• Linux Filesystem - tree of files rooted at a special root directory (/), for example:

• advantage of tree structures is that we can uniquely specify location of any file by giving path taken to reach file from root
• A path ending with / indicates that we have a path to a directory, but the Linux file system does not require that paths to directories terminate with / (this is our convention)

Naming Files