Unix/Linux shells

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?