ult: Add content on shell variables and comments.

2 files changed, 50 insertions, 0 deletions

diff --git a/ult/handout.rst b/ult/handout.rst
index a1ea9fb..5ef762a 100644
--- a/ult/handout.rst
+++ b/ult/handout.rst
@@ -1785,6 +1785,41 @@ So, these are all the paths that are searched, when looking to execute a
 command. If we put the results.sh script in one of these locations, we
 could simply run it, without using the ``./`` at the beginning. 
 
+Variables
+---------
+
+As expected, it is possible to define our own variables inside our shell
+scripts. For example,
+
+::
+
+    name="FOSSEE"
+
+creates a new variable ``name`` whose value is ``FOSSEE``. To refer to this
+variable, inside our shell script, we would refer to it, as ``$name``.
+**NOTE** that there is no space around the ``=`` sign. 
+
+::
+
+    ls $name*
+
+It is possible to store the output of a command in a variable, by enclosing
+the command in back-quotes. 
+
+::
+
+    count=`wc -l wonderland.txt`
+
+saves the number of lines in the file ``wonderland.txt`` in the variable
+count. 
+
+Comments
+--------
+
+The ``#`` character is used to comment out content from a shell script.
+Anything that appears after the ``#`` character in a line, is ignored by
+the bash shell. 
+
 Control structures and Operators
 ================================
 
diff --git a/ult/ult.tex b/ult/ult.tex
index 613409f..a94dc14 100644
--- a/ult/ult.tex
+++ b/ult/ult.tex
@@ -1013,6 +1013,21 @@
 \end{frame}
 
 \begin{frame}[fragile]
+  \frametitle{Variables \& Comments}
+  \begin{lstlisting}
+    $ name=FOSSEE
+    $ count=`wc -l wonderland.txt`
+    $ echo $count # Shows the value of count
+  \end{lstlisting} % $
+  \begin{itemize}
+  \item It is possible to create variables in shell scripts
+  \item Variables can be assigned with the output of commands
+  \item \alert{NOTE:} There is no space around the \texttt{=} sign
+  \item All text following the \texttt{\#} is considered a comment
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]
   \frametitle{\texttt{echo}}
   \begin{itemize}
   \item \texttt{echo} command prints out messages