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Tutorial8: Links / Process Management

903 bytes added, 21:02, 25 October 2021
Undo revision 156312 by Jason Michael Carman (talk)
===Aliases / Command History===
<br>'''AliasAliases:'''<br><br>Assigns An '''alias''' is a '''nickname ''' to an existing command or group of commands.<br><br>An alias existing in '''system memory''' and will be '''lost''' when your current Linux session ends,<br>unless the alias is set in a '''start-up file''' (e.g. <span style="font-family:courier;font-weight:bold;">~/.bashrc</span>. You will learn about using start-up files <u>later</u> in this course.<br><br>
''Examples:''
'''Command History:'''
<br><br>The filename '''<span style="font-family:courier;font-weight:bold;>~/.bash_history''' </span> stores recently executed command lines
<br><br>
''Examples of commands that use command history:''
<table width="80%"><tr valign="top"><td width="30%"><span style="font-family:courier;font-weight:bold;>up arrow</span> or <span style="font-family:courier;font-weight:bold;>down arrow</span> </td><td>move to '''previous''' command or '''next''' command within Bash shell prompt</td></tr><tr><td><span style="font-family:courier;font-weight:bold;>fc -l</span></td><td> display last '''16''' commands</td></tr><tr><td><span style="font-family:courier;font-weight:bold;>history | more</span></td><td>display all stored commands</td></tr><tr><td><span style="font-family:courier;font-weight:bold;>!num</span></td><td>'''re-execute''' an issued command number by command number (determined from ''history'' command)</td></tr><tr><td><span style="font-family:courier;font-weight:bold;>!xxx</span></td><td>'''re-executerun''' an a most recent previously-issued command beginning with string "xxx"</td></tr></table><br><br>
=INVESTIGATION 1: LINKING FILES=
<span style="color:red;">'''ATTENTION''': Depending on your ULI101 instructor, you may be required to complete this tutorial for '''marks''' in this course.<br>Please refer to your instructor's course notes and lecture notes regarding evaluation for this course.<br><br>The due date for successfully completing this tutorial (i.e. '''tutorial 8''') is by '''Friday by midnight''' next week (i.e. '''Week 8''').<br>If your instructor has NOT assigned marks for completing this tutorial, you can perform it for '''practice'''.</span><br><br> In this sectioninvestigation, you will learn how to create '''hard links''' and '''symbolic links''' on your Matrix account,<br>and observe the <u>advantages</u> and <u>limitations</u> of using both types of links.
# Issue the following Linux command to create a hard-linked file in your '''home''' directory:<br><span style="color:blue;font-weight:bold;font-family:courier;">ln ~/links/data-file.txt ~/data-file.hard.lnk<br><br>
# Issue the following Linux command to compare all file's ''i-node'' numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls -li ~/links/data-file.txt ~/links/data-file.hard.lnk ~/data-file.hard.lnk</span><br><br>What do you notice about all of those file's ''i-node'' numbers?<br><br>
# Issue the following Linux command to check that you created those hard links: <br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/myscripts~uli101/week8-check-1</span><br><br>If you encounter errors, then view the feedback to make corrections, and then re-run the checking script.<br>If you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br>
# Issue the following Linux command to remove the '''~/links''' directory and its contents: <br><span style="color:blue;font-weight:bold;font-family:courier;">rm -rf ~/links</span><br><br>
# Issue a Linux command to confirm that the '''~/links''' directory has been removed.<br><br>
# Save your editing session and exit your text editor.<br><br>
# Issue the following Linux command to view the contents of the '''symbolic''' linked file:<br><span style="color:blue;font-weight:bold;font-family:courier;">cat ~/links2/text-file.sym.lnk</span><br><br>What did you notice? Again, when you view the contents of the symbolic-linked file,<br>you are redirected (via ''pathname'') to the <u>original</u> file.<br><br>
# Issue the following Linux command to check that you created those symbolic links: <br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/myscripts~uli101/week8-check-2</span><br><br>If you encounter errors, then view the feedback to make corrections, and then re-run the checking script.<br>If you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br>
# Issue the following Linux command to remove the '''~/links2''' directory: <br><span style="color:blue;font-weight:bold;font-family:courier;">rm -rf ~/links2</span><br><br>
# Issue a Linux command to confirm that the '''~/links2''' directory has been removed.<br><br>
=INVESTIGATION 2: MANAGING PROCESSES =
In this sectioninvestigation, you will learn how to '''manage processes''' on a Unix / Linux server.
<br>
In this sectioninvestigation, you will learn how to '''manage aliases''' and '''Linux command history''' on your Matrix account.
# Reissue the '''lh''' alias. What happened? Why?<br><br>
# Reissue the '''lal''' alias. Why '''didn't''' this alias work?<br><br>The checking script below is designed to act as a '''filter''' with a '''pipeline command'''.<br>This will allow to check if your '''lh''' alias exists when it is checked in this program.<br><br>
# Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">alias | bash /home/murray.saul/myscripts~uli101/week8-check-3</span><br><br>If you encounter errors, then view the feedback to make corrections, and then re-run the checking script.<br>If you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br>We will complete this investigation by learning to execute p'''reviously issued commands''' by using '''command history'''.<br><br>
# Issue the following Linux command: <span style="color:blue;font-family:courier;font-weight:bold">history | grep "lh"</span><br><br>What do you notice?<br><br>
# Type an exclamation mark '''!''' followed by the number by one of those commands<br>listed in the '''history list''' and press <span style="color:blue;font-family:courier;font-weight:bold">ENTER</span><br><br>What happened?<br><br>

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