\subsection{Examples}While the PUSH shell handles much of the complexity of interacting with theBrasil infrastructure, it is useful to see examples of how it interactswith the underlying infrastructure in order to understand the various mechanismsbetter.  These examples are given from the perspective of directly interactingwith the infrastructure file systems from a normal UNIX shell. The first example presents how the default aggregation behaviour of Brasil canused to deploy large number of applications. \begin{verbatim}$ less ./mpoint/csrv/local/clone0 \end{verbatim}The above command is an example of creating a new session. The contents readfrom the \texttt{[clone]} file represent the session-ID.  Now we use session 0for performing actual execution.\begin{verbatim}$ echo "res 4" > ./mpoint/csrv/local/0/ctl$ echo "exec date" > ./mpoint/csrv/local/0/ctl$ cat ./mpoint/csrv/local/0/stdioFri May 7 13:53:58 CDT 2010Fri May 7 13:53:58 CDT 2010Fri May 7 13:53:58 CDT 2010Fri May 7 13:53:58 CDT 2010$\end{verbatim}The first echo command sends the request for reserving 4 remote resources. Thenext echo command submits the request for executing the \texttt{date} command.And the \texttt{cat} command on \texttt{[stdio]} returns the aggregated outputto the user.  This example shows all the complexities about finding, connectingand using the remote resources is hidden behind the filesystem interface.This approach can be used in the \textit{trivially parallelizable applications}where the same application is deployed on all the nodes. When constructing more complicated dataflow pipelines, Brasil handlesreserving the resources and setting up the pipe endpoints of the pipelinecomponents.Instead of interacting with the aggregation points, dataflow applications (suchas the PUSH shell) can interact directly with the subsessions responsible for each pipeline component. In this example, we will try to create a small pipeline of two commands\texttt{date | wc}.  But we will create this pipeline across multiple nodes.  Lets assume that session 0 is created by opening \texttt{[clone]} file as shownin the previous example.  The following commands will create the desiredpipeline. \begin{verbatim}$ echo "res 2" > ./mpoint/csrv/local/0/ctl$ echo "exec date" > ./mpoint/csrv/local/0/0/ctl$ echo "exec wc" > ./mpoint/csrv/local/0/1/ctl$ echo "xsplice 0 1" > ./mpoint/csrv/local/0/ctl$ cat ./mpoint/csrv/local/0/1/stdio1 6 29$\end{verbatim} The first command \texttt{[exec date]} is sent to 0'th sub-session and thesecond command \texttt{[exec wc]} is sent to the 1st sub-session.  The\texttt{[xsplice 0 1]} request tells the parent session to redirect the outputof the 0'th session to the input of the 1st session.  The \textbf{xsplice}command can be seen as a pipe operator of the shell script for redirecting theoutput of one command to the input of other command. The above example is equivalent of executing \texttt{date | wc} on the shell,but with the difference that both commands are executed on a different remotemachines while sharing the same namespace.