Linux Tutorial Step 4 Create and run a script

Step 4 -- Create and run a script

Before we create a batch script and submit it to a compute node, we will do something a bit simpler. We will create a regular script file that will be run on the login node. A script is just a file that consists of UNIX commands that will run when you execute the script file. It is a way of gathering together a bunch of commands that you want to execute all at once. You can do some very powerful things with scripting to automate tasks that are tedious to do by hand, but we are just going to create a script that contains a few commands we could easily type in. This is to help you understand what is happening when you submit a batch script to run on a compute node.

Use a text editor to create a file named "tutorial.sh" which contains the following text (note that with emacs or nano you can use the mouse to select text and then paste it into the editor with the middle mouse button):

$ nano tutorial.sh
echo ----
echo Job started at `date`
echo ----
echo This job is working on node `hostname`

SH_WORKDIR=`pwd`
echo working directory is $SH_WORKDIR
echo ----
echo The contents of $SH_WORKDIR
ls -ltr
echo
echo ----
echo
echo creating a file in SH_WORKDIR
whoami > whoami-sh-workdir

SH_TMPDIR=${SH_WORKDIR}/sh-temp
mkdir $SH_TMPDIR
cd $SH_TMPDIR
echo ----
echo TMPDIR IS `pwd`
echo ----
echo wait for 12 seconds
sleep 12
echo ----
echo creating a file in SH_TMPDIR
whoami > whoami-sh-tmpdir

# copy the file back to the output subdirectory
cp ${SH_TMPDIR}/whoami-sh-tmpdir ${SH_WORKDIR}/output

cd $SH_WORKDIR

echo ----
echo Job ended at `date`

To run it:

$ chmod u+x tutorial.sh
$ ./tutorial.sh

Look at the output created on the screen and the changes in your directory to see what the script did.