This homework will assess your ability to run commands in the shell and make a simple script.
Replace the lines specified in italics with your answers and save as a text file.
60 points
Complete the interactive tutorial.
Did you hit any points of frustration, and if so, how could we improve the material to avoid that frustration?
20 points
Learn about the difference between standard out (“stdout”) and standard error (“stderr”) from this article (feel free to read the whole thing, but you can stop before the section “Detecting Redirection Within a Script”).
Note that in reading this article, you don’t need to come up with a script that will throw an error: we have one at tfcb_2021/lectures/lecture03/06-scripting/script2.sh.
Write a command here that redirects stdout from script2.sh to a file named stdout.txt and redirects stderr to a file named stderr.txt.
20 points
You might have noticed that the files we’re dealing with have “extensions” that describe their file type.
For example, text files are marked with .txt, and shell scripts are labeled with .sh.
This is a handy convention which is used heavily by a command-line library called imagemagick to manipulate images. ImageMagick has been installed on rhino, but needs to be loaded before you use it:
ml ImageMagick
Don’t forget to load the updated version of parallel:
ml parallel
Once the library is loaded, go to the lecture03/slides/images directory and try
convert betty-crocker.jpg betty-crocker.png
which converts betty-crocker.jpg (a JPG image) to betty-crocker.png (a PNG image).
You can confirm proper conversion using file.
Now, your turn:
Use parallel to convert all of the JPGs in this directory to PNG images.
Big hint: There is a very similar sort of command in the “Compute intensive jobs and substitution” section of the parallel man page.
Next:
Write a script that will take all of the JPGs in the current directory, convert them to PNGs, and then assemble all of the PNGs in the current directory into a file called montage.png using the montage command. Paste that script here.