teaching machines

CS 330 Lecture 3 – Shell Scripting, Part 2

January 27, 2017 by Chris Johnson. Filed under cs330, lectures, spring 2017.

Dear students,

We will continue to work with the shell, a world between worlds. A place full of dead mice. Let’s start with a reading review:

1. What does it mean for a directory to be executable?
2. Write a command to run program place, reading from file bets and appending its output to file log.
3. What will file .. report?
4. Your program webify generates a lot of HTML. Write a command to only show the img tags.

Now it’s time for a segment I like to call What Does This Do? We’ll spend a moment absorbing each code snippet, and then I’ll ask what they do and what would be a good name for the script.

• WDTD #1

  for i in $@; do
    mv $i $(date +%Y%m%d)_$i
  done

• WDTD #2

  base=$(basename -s .c $1)
  gcc -o $base $1 && ./$base

• WDTD #3

  yes "Got get 'em." | head -n 15

Then we’ll write some scripts:

1. Bookmark a directory for later return.
2. Send files to limbo/recycling bin, rather than hell/non-existence.
3. Send a mass email.
4. Show the biggest files in a directory.
5. Upload a local file to a web server and let the world see it.

Here’s your TODO list for next time:

• Install Ruby on your Linux installation. Ruby is often installed per user, and one user may have several versions installed. I recommend you do the same. The following shell commands will install RVM (the Ruby Version Manager) and Ruby 2.3.3.

  gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
  \curl -sSL https://get.rvm.io | bash -s stable
  rvm install 2.3.3
  ruby --version

• Watch Introduction to Ruby until at least 17:25.

Sincerely,

big

#!/bin/bash

du -s * | sort -nr | head

redir

#!/bin/bash

cd $(cat ~/.dirmark)

save

#!/bin/bash

pwd > ~/.dirmark