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Unix/Linux shells. 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.”
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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
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.
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
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.)