Terms you need to know before starting with Shell scripting :
POSIX : 
<ul>
<li>As you already know that Unix is/was Open source from the begining , which allowed devolopers/users to write their own programs and issues that arised out of it were 
grep on one system used –i to mean “ignore case when searching,” and it used –y on another variant to mean the same thing! This sort of thing happened with multiple utilities,not just a few.
So POSIX was introduced for standardization. So whatever Linux/Unix software that you see in the market should be POSIX complaint.</li>
</ul>
<ul>
<li>POSIX isnt the only standardization for Unix , there were other standards too such as 
XPG4 , but it was less rigorous when compared to POSIX and it was Super set of POSIX(which meant it had broader range of practices). </li>
</ul>
<ul>
<li>After that final version of POSIX was released which encompassed XPG4 as well , and now considered as "Single UNIX Standard"</li>
</ul>
<ul>
<li>By using just POSIX-specified features,you have a good chance of being able to
move your script, unchanged, to different kinds of systems.</li>
</ul>
So it is important to learn UNIX according to POSIX. 
#HappyLearning :)

Terms you need to know before starting with Shell scripting :

**POSIX :** 

- 
 As you already know that Unix is/was Open source from the begining , which allowed devolopers/users to write their own programs and issues that arised out of it were 
grep on one system used –i to mean “ignore case when searching,” and it used –y on another variant to mean the same thing! This sort of thing happened with multiple utilities,not just a few.
So POSIX was introduced for standardization. So whatever Linux/Unix software that you see in the market should be  POSIX complaint.



- 
 POSIX isnt the only standardization for Unix , there were other standards too such as 
XPG4 , but it was less rigorous when compared to POSIX and it was Super set of POSIX(which meant it had broader range of practices). 



- 
 After that final version of POSIX was released which encompassed XPG4 as well , and now considered as "Single UNIX Standard"


- 
By using just POSIX-specified features,you have a good chance of being able to
move your script, unchanged, to different kinds of systems.

So it is important to learn UNIX according to POSIX. 

#HappyLearning :)


POSIX (Unix History)