UNIX/LINUX SHELLS

 “A Unix shell is a command-line interpreter or shell that provides a traditional user interface for the Unix operating system and for Unix-like systems.”  “Users direct the operation of the computer by entering commands as text for a command line interpreter to execute or by creating text scripts of one or more such commands.”  from wikipedia SHELLS

 most popular:  sh  written by (Stephen) Bourne shell, 1977  csh  written Bill Joy  bash  Bourne Again shell (Unix, Linux, Mac OS)  others:  ash, dash, es, fish, ksh, mksh, psh, rc, scsh, tcsh, zoidberg, zsh SHELLS

WHICH SHELL IS MY DEFAULT SHELL?

 When you log in, the shell will load your configuration file (if present).  These files start with a period (.) and should be located in your home directory, (~).  These files are not listed by ls by default. (They are “invisible.”) To have ls list them, use the –a option.  Use.cshrc for csh; use.bashrc for bash. CONFIGURATION FILES

EXAMPLE.CSHRC

EXAMPLE.BASHRC

 setenv (csh) vs. export (bash)  setenv PATH /home/ggrevera/mpich2-install/bin:$PATH  export PATH=/usr/ccs/bin:$PATH  alias (csh) vs. alias (bash)  alias emacs /home/ggrevera/emacs-23.4/src/emacs  alias emacs=/home/ggrevera/emacs-23.4/src/emacs DIFFERENCES BETWEEN CSH AND BASH

 To run a shell, simply type its name.  bash  To exit a shell, simply enter the exit command.  exit  (When you exit your last shell, you will log out of the system.) HOW DOES ONE RUN/EXIT A SHELL?