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Unix/Linux shells

A Unix shell is a command-line interpreter that provides a traditional user interface for Unix and Unix-like systems. Users interact with the computer by entering commands as text for the shell to execute or by creating text scripts. Some of the most popular shells include sh (Bourne shell), csh (C shell), and bash (Bourne Again shell). Configuration files, which start with a dot and are located in the user's home directory, customize shell behavior. Users can run a shell by typing its name and exit by entering the "exit" command.

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Unix/Linux shells

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  1. Unix/Linux shells

  2. 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

  3. 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

  4. Which shell is my default shell?

  5. Configuration files • 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.

  6. Example .cshrc

  7. Example .bashrc

  8. Differences between csh and bash • setenv (csh) vs. export (bash) • setenvPATH /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

  9. How does one run/exit a shell? • 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.)

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