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Users can '''manage processes''' to become more '''productive''' while working in the Unix / Linux Command-line environment. <br>Processes that run in the terminal are known as ''Common 'foreground''' processes. You can run or send processes currently running<br>in the ''foreground'' to the '''background''' to free-up your terminal (e.g. issue other Linux commands / ).<br><br>Below are a listing of common '''Linux commands''' and '''keyboard shortcuts ''' to manage foreground and background processes:''
<table cellpadding="5" width="80%"><tr valign="top"><th width="25%" style="border-bottom: 1px solid black;text-align:left;">Linux Command /<br>Key Combination</th><th style="border-bottom: 1px solid black;text-align:left;">Purpose</th></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">ps</span></td><td>Displays snapshot information about processes.<br>''Examples: ''<span style="font-family:courier;font-weight:bold">ps , ps -l , ps -ef , ps -u , ps aux</span><br></td></tr><tr valign="top"><td>'''<span style="font-family:courier;font-weight:bold;">top</span>'''</td><td>The '''top''' command provides a realtime status of running processes.<br>'''NOTE:''' You can press '''ctrl-c''' to exit<br></td></tr><tr valign="top"><td><span style="font-family:courier;">'''ctrl-c'''</span></td><td>'''Terminates''' a process running in the foreground</td></tr><tr valign="top"><td><span style="font-family:courier;">'''ctrl-z'''</span></td><td>Sends a process running in the foreground into the '''background'''.</td></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">fg</span></td><td>Moves a background job from the current environment into the foreground.<br>''Example: ''<span style="font-family:courier;font-weight:bold">fg %job-number</span></td></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">bg</span></td><td>Runs (starts) the most recent process that was placed into the background.<br>''Example: ''<span style="font-family:courier;font-weight:bold">bg %job-number</span></td></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">jobs</span></td><td>The '''jobs''' utility displays the '''status''' of jobs that were started in the current shell environment. ''Example:<br>''<span style="font-family:courier;">jobs<br>[1]+ Stopped vim a <span style="font-size:8pt;"> <-- Job #1 (+ most recent process / background)</span><br>[2] Running sleep 200 & <span style="font-size:8pt;"> <-- Job #2</span><br>[3] Running sleep 300 & <span style="font-size:8pt;"> <-- Job #3</span><br>[4]- Running sleep 400 &<span style="font-size:8pt;"> <-- Job #4 (- second recent process / background)</span><br><br></span></td></tr><tr valign="top"><td><span style="font-family:courier;font-weight:bold;">kill</span></td><td>The kill command sends the specified signal to the specified processes or process groups. If no signal is specified, the '''TERM''' signal is sent. The default action for this signal is to terminate the process.<br>''Examples:''<br><span style="font-family:courier;font-weight:bold;">kill PID , kill -9 PID , kill %job-number , <br>kill -9 %job-number</span></td></tr></table>
===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
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''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.
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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>
