Mac OS X Leopard - ARCAism

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CHAPTER 18 INTRODUCING DARWIN AND THE SHELL
NOTE Traditionally, things in the profile files would get read when you logged into a terminal,
and things in the bashrc files would get read each time you launched a new shell. This isn’t
exactly how these things work anymore, but it’s still nice to keep the content of each separate.
One common environmental variable that you may want to set is the $PATH variable. The
$PATH variable describes where your shell will look for executables when you attempt to launch
one from the command line. By default, your $PATH is set to include /bin, /sbin, /usr/bin,
/usr/sbin, and /usr/X11/bin (in the /etc/profile file). However, if you begin to install new executables,
or even write your own, you may find that you need to add additional directories to
your $PATH. The syntax to add a directory to the $PATH is as follows:
$PATH=/new/directory:/another/new/direcotry:"${PATH}"
You can add as many directories as you need, separated by a colon. The "${PATH}" at the end
represents your existing path; without it, any of the default $PATH directories will be removed
from your $PATH. To have your path updated each time you launch a shell, it’s best just to put this
info in your .bash_profile. For example, my current .bash_profile looks like this:
### .bash_profile ###
# a good place for environmental variables #
### $PATH ###
if [ -d /usr/local/bin ] ; then
PATH=/usr/local/bin:"${PATH}"
fi
if [ -d /usr/local/mysql/bin ] ; then
PATH=/usr/local/mysql/bin:"${PATH}"
fi
if [ -d ~/bin ] ; then
PATH=~/bin:"${PATH}"
fi
if [ -d /opt/local/bin ] ; then
PATH=/opt/local/bin:"${PATH}"
fi
### include .bashrc if one exists ###
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
Any line beginning with # is a comment. Here I use some of the built-in scripting functionality
to check if common executable directories exist—if they do, then they are automatically
added to my $PATH.
The last part checks to see if I have a .bashrc file, and if I do, it includes that as well.
The bashrc files generally contain variables and commands that are specific to the shell. For
example, the default /etc/bashrc file sets the prompt variable. Other things that are generally
included in the bashrc files are common aliases and shell functions.
For example, my current OS X .bashrc file is simply the following:
### .bashrc file ###
# This file is for shell-specific stuff #
# $PATH and other env variables should go in the .bash_profile #