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=====unix Keyword 2=====
shabang

====Definition==== 
A **shabang** is this: //#!//
The **shabang** is used to read the following test on the first line after it to determine what interpreter the user would like to... use.
Some example of interpreters (Taken directly from  http://en.wikipedia.org/wiki/Shebang_(Unix):
  * #!/bin/bash -- Execute the file using sh, the Bourne shell, or a compatible shell
  * #!/bin/csh -- Execute the file using csh, the C shell, or a compatible shell
  * #!/usr/bin/perl -T -- Execute using Perl with the option for taint checks
  * #!/usr/bin/php -- Execute the file using the PHP command line interpreter
  * #!/usr/bin/python -0 -- Execute using Python with optimizations to code
  * #!/usr/bin/ruby -- Execute using Ruby
====References====

  * http://en.wikipedia.org/wiki/Shebang_(Unix)


=====unix Keyword 2 Phase 2=====
PATH environment variable

====Definition====
The $PATH variable specifies a list of one or more directory names separated by colons.

The /bin, /usr, and /local directories are typically included in most users' $PATH settings. The current directory is sometimes included, allowing programs in the current directory to be executed. Superuser (root) accounts as a rule are not include in $PATH, however, in order to prevent the accidental execution of scripts in the current directory.

When a command name is specified by the user or an exec call is made from a program, the system searches through $PATH, examining each directory from left to right in the list, looking for a filename that matches the command name. Once found, the program is executed as a child process of the command shell or program that issued the command.
====References====
http://en.wikipedia.org/wiki/PATH_%28variable%29


====Demonstration====
The following is an example of a **$PATH**:
<cli>
lab46:~/src/opus/opus2$  
</cli>
The **$PATH**
The //home// directory (~/) is the beginning of this specified **$PATH**, followed by the //src// directory, then the //opus// directory, and lastly the //opus2// directory.
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