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Tutorial 10 - Shell Scripting - Part 1

4,263 bytes added, 13:36, 14 November 2021

→‎INVESTIGATION 1: CREATING A SHELL SCRIPT

= INVESTIGATION 1: CREATING A SHELL SCRIPT =

'''ATTENTION''': The due date for successfully completing this tutorial (i.e. tutorial 8) is by Friday, December 15 @ 11:59 PM (Week 14).

In this investigation, you will learn how to create and run a '''Bash Shell script'''.

'''Perform the Following Steps:'''

# '''Login''' to your matrix account.

# Issue a command to '''confirm''' you are located in your '''home''' directory. We want to create a Bash Shell script to welcome the user by their ''username''. Let's first look at selecting an appropriate filename for your shell script.

# Issue the following linux command to check if the filename called '''hello''' already exists as a command: which hello The output from this command should indicate that the shell did NOT find any directories that contained this filename that could represent a command; therefore, this shell script name CAN be used. [[Image:hello0.png|thumb|right|200px|Using a '''text editor''' to add Linux commands in to the '''hello''' shell script.]]

# Use a '''text editor''' like '''vi''' or '''nano''' to create the text file called '''hello'''

# Enter the following two lines in your shell script: echo echo "Hello $USER" echo '''NOTE:''' The variable called '''USER''' is an '''environment variable''' that contains the current user's login name. If you wanted to share your shell script with other users, when they run the shell script, they will greeted by their username. ''Environment variables'' make your shell script adaptable by ALL users.

# '''Save''' your editing session and '''exit''' the text editor. Instead of issuing the '''bash''' command followed by your shell script pathname as an ''argument'', let's simply run it by its filename. This is the most common method of running shell scripts. <table align="right"><tr valign="top"><td>[[Image:no-execute.png|thumb|right|230px|An '''error message''' will appear when trying to run a shell script by name that does NOT have '''execute''' permissions.]]</td><td>[[Image:hello1.png|thumb|right|150px|Output from running your '''hello''' shell script (YourUserID representing your username).]]</td></table>

# Issue the following linux command to run your shell script in your current directory: ./hello You should notice an '''ERROR message''' indicating you don't have permissions to run the file. To fix this, you need to '''add execute permissions''' prior to running the shell script.

# Issue the following linux command to '''add''' execute permissions for your shell script: chmod u+x hello

# Issue the following to run your shell script: ./hello Did your shell script run? '''ATTENTION:''' Students might get FRUSTRATED when performing their '''assignment 3''' when their Bash shell scripts have errors. One major cause is the the OUTPUT of their Bash shell script when run does not '''EXACTLY match''' the required output for the '''correct''' Bash shell script. This requires that you CAREFULLY '''read''' the requirements of your Bash shell script and create it to the EXACT specifications

# Issue the following Linux command to run a checking script: ~osl640/week10-check-1

# If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed.

::In the next investigation, you will learn to create and run shell scripts that use '''variables''', '''positional''' and '''special parameters'''. You will also learn how to add a '''she-bang line''' at the top of a shell script to force it to run in a specified shell. Proceed to the next investigation.

= INVESTIGATION 2: USING VARIABLES IN SHELL SCRIPTS =

Jason Michael Carman

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Tutorial 10 - Shell Scripting - Part 1

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