Shell Scripting

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Introduction to Linux in HPC/Shell scripting
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Tutorial
Title: Introduction to Linux in HPC
Provider: HPC.NRW

Contact: tutorials@hpc.nrw
Type: Multi-part video
Topic Area: HPC Platforms
License: CC-BY-SA
Syllabus

1. Background and History
2. The Command Line
3. Linux Directory Structure
4. Files
5. Text display and search
6. Users and permissions
7. Processes
8. The vim text editor
9. Shell scripting
10. Environment variables
11. System configuration
12. SSH Connections
13. SSH: Graphics and File Transfer
14. Various tips

In this video the concept of shell scripting is introduced. Commands entered into the console can also be written into a text file to create an executable script. The tutorial will describe how to create such a script, explain its basic structure and how to execute it in the console.

Video

( Slides as pdf)

Quiz

Which command rund the executable script "test.sh" located in your home folder?

~$ test.sh
~$ ./test.sh
~$ ~/test.sh

Which bash command below assigns "value" to variable var?

var="value"
var = "value"
var=="value"

What do you have to add to the header of a script to make it an executable bash script?

#BASH
/bin/bash
#!/bin/bash

How can you de-reference the second command-line argument in a script when calling ~$ ./test.sh arg1 arg2 arg3?

$arg2
$1
$arg1
$2
$0

Exercises in Terminal

1. Write a script that:
   a. Prints an environment variable
   b. Saves the output of the date command to a variable
   c. Sleeps for 2 seconds
   d. Prints the new and old date and time
2. Find a way to execute a script without setting execute permissions.
3. Find out how to do other programming things in bash (e.g. functions, classes). How convenient do they look?
4. Look at different ways you can define if conditions.
5. Find out what different types of quotes (single ' vs. double ") do?
6. Create an shell variable MYIDENTITY and export it as below: 
   $ export MYIDENTITY=whoami
   How will you list the shell variable MYIDENTITY?
   Execute the shell variable MYIDENTITY, what is the output? 



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