1,234
edits
Changes
no edit summary
{{Admon/caution|DO NOT USE THIS VERSION OF THE LAB. This page will no longer be updated.|'''New version here:''' https://seneca-ictoer.github.io/ULI101/A-Tutorials/tutorial5<br />'''Andrew's students please go here:''' http://wiki.littlesvr.ca/wiki/OPS145_Lab_5}}
=REDIRECTION: STANDARD INPUT / STANDARD OUTPUT / STANDARD ERROR=
<br>
|- valign="top" style="padding-left:15px;"
|colspan="2" |Course Notes'''Slides:'''<ul><li>Week 5 Lecture 1 Notes:<br>[https://ictwiki.cdot.senecacollege.ca/~murrayuli101/slides/ULI101-5.1.pdf PDF] | https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-5.1.pptx PPTX]</li><li>Week 5 Lecture 2 Notes:<br> [https://wiki.cdot.senecacollege.saulca/uli101/slides/ULI101-Week55.2.pdf PDF] | [https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101slides/ULI101-Week55.2.pptx PPTX]<br></li></ul>
| style="padding-left:15px;" |'''Redirection:'''
* [http://www.linfo.org/standard_input.html Standard Input (stdin)]
* [http://www.linfo.org/standard_output.html Standard Output (stdout)]
* [http://www.linfo.org/standard_error.html Standard Error (stderr)]
* [http://www.linfo.org/pipe.html Pipeline Commands]<br><br>
'''Multiple Commands:'''
* [https://www.javatpoint.com/linux-semicolon Semicolon]<br>
* [https://www.gnu.org/software/bash/manual/html_node/Command-Grouping.html Grouping ( )]<br><br>
| style="padding-left:15px;"|'''Redirection Filters:'''
* [http://man7.org/linux/man-pages/man1/more.1.html more] , [http://man7.org/linux/man-pages/man1/less.1.html less]<br>
* [http://man7.org/linux/man-pages/man1/head.1.html head] , [http://man7.org/linux/man-pages/man1/tail.1.html tail]
* [http://man7.org/linux/man-pages/man1/tee.1.html tee]<br>
|colspan="1" style="padding-left:15px;" width="30%"|'''Brauer Instructional Videos:'''<ul><li>[https://www.youtube.com/watch?v=ocU34PcYn2U&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=4 Reading/Writing to Files<br>(echo, stdin, stdout, stderr, >, >>, 2>, cat, more, less, man, date, diff, diff -y, find, wc])<br></li></ul>
|}
<table align="right"><tr><td>[[Image:stdout-symbol-1.png|thumb|right|250px|The '''standard inputout''' ('''stdinstdout''') symbol with one greater than sign '''overwrites''' existing file content with command output]]</td><td>[[Image:stdout-symbol-2.png|thumb|right|250px|The '''standard inputoutput''' ('''stdinstdout''') symbol with two greater than signs '''add''' command's output to '''bottom''' of existing file's contents.]]</td></tr></table>
'''Standard output''' ('''stdout''') describes where a command sends its '''output'''.<br>In the examples below, output from a command is sent to the '''monitor''', unless it is sent to a '''text file'''.
=INVESTIGATION 1: BASICS OF REDIRECTION=
<span style="color:red;">'''ATTENTION''': This online tutorial will be required to be completed by '''Friday in week 6 by midnight''' to obtain a grade of '''2%''' towards this course</span><br><br> In this sectioninvestigation, you will learn how to redirect '''standard input''', '''standard output''' and '''standard error''' when issuing Unix / Linux commands.
# Press <span style="color:blue;font-weight:bold;font-family:courier;">ctrl-d</span> to exit the command.<br><br>
# Issue the '''cat''' command to view the contents of the file: '''output3.txt'''<br><br>
# Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">cp ~murrayjason.saulcarman/uli101/cars .</span><br><br>
# Issue the '''cat''' command to view the contents of the '''cars''' file.<br><br>
# Issue the following Linux command: <span style="color:blue;font-weight:bold;font-family:courier;">cut -c1-10 cars</span><br><br>What did this command do?<br><br>
# Issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep 2 <<+<br>line 1<br>line 2<br>line 3<br>+</span><br><br>What do you notice? How does this differ from the previous command? Why?<br><br>
# Issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep 2 > line2.txt <<+<br>line 1<br>line 2<br>line 3<br>+</span><br><br>What do you notice? What is contained in the file '''line2.txt'''? Why?<br><br>'''NOTE:''' You will now run a shell script to confirm that you properly issued Linux commands using redirection.<br><br>
# Issue the following Linux command to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/scripts~uli101/week5-check-1</span><br><br>
# If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed.<br><br>
# Issue the '''ls''' command to see all of the '''temporary files''' that were created as a result of redirection.<br><br>The problem with using these redirection symbols is that you create '''temporary text files''' that take up '''space''' on your file system.<br><br>
# Issue a Linux command (using '''Filename Expansion''') to '''remove''' those temporary text files in the current directory.<br><br>
# Issue the following Linux command to check that you removed ALL of those temporary text files:<br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/scripts~uli101/week5-check-2</span><br><br>
# If you encounter errors, make corrections and '''re-run''' the checking script until you receive a congratulations message, then you can proceed.<br><br>
=INVESTIGATION 2: REDIRECTION USING PIPELINE COMMANDS =
In this sectioninvestigation, you will learn to issue '''pipeline commands''' to to accomplish tasks <u>without</u> having to generate temporary files.
# Issue the '''ls''' command.<br><br>You should notice that '''no files have been created'''.<br>Let's get practice issuing more pipeline commands using commands<br>(previously learned or new) to be used as '''filters'''.<br><br>
# Issue the following Linux '''pipeline command''': <span style="color:blue;font-weight:bold;font-family:courier;">ls /bin/?? | sort | head -5</span><br><br>What did you notice?<br><br>
# Issue the following Linux '''pipeline command''': <span style="color:blue;font-weight:bold;font-family:courier;">ls /bin/???? | sort | grep r | tail -2</span><br><br>What did you notice? Could you predict the output prior to issuing this pipeline command?<br><br>
# Issue the following Linux '''pipeline command''': <span style="color:blue;font-weight:bold;font-family:courier;">ls /bin/???? | sort | grep r | cut -c1-6</span><br><br>Try to explain step-by-step each process in the pipeline command (including ''filters'')<br>to explain the final output from this pipeine command.<br><br>
# Confirm that you are still located in the '''~/redirect''' directory.<br><br>
# Issue the following Linux '''pipeline command''':<br><span style="color:blue;font-weight:bold;font-family:courier;">ls /bin/???? | tee unsort.txt | sort | tee sort.txt | grep r | tee match.txt | head </span><br><br>
# Issue the '''ls''' command to view the contents of this redirectory.<br><br>What did you notice?<br><br>
# View the <u>contents </u> of the '''text files ''' that were created to see how the '''tee''' command<br>was used in the previous pipeline command.<br><br>What was the purpose of using the '''tee''' command for this pipeline command?<br><br>You will now run a shell script to confirm that you properly issued that Linux pipeline command<br>using the '''tee''' command and redirection.<br><br># Issue the following Linux command to run a checking script:<br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/scripts~uli101/week5-check-3</span><br><br>If you encounter errors, make corrections and '''re-run''' the checking script until you receive<br>a congratulations message, then you can proceed.<br><br>
# Change to <u>your</u> '''home''' directory.<br><br>
# Remove the '''~/redirect''' directory and its contents.<br><br>
:In the next investigation, you will learn various techniques to issue '''multiple Linux commands'''<br>on the same line, or long issue a '''single Linux commands command over multiple lines'''.
<br><br>
=INVESTIGATION 3: ISSUING MULTIPLE UNIX/LINUX COMMANDS=
In this sectioninvestigation, you will learn how to issue multiple Unix / Linux commands in a single line or over multiple lines.
'''Perform the Following Steps:'''
# Confirm you are located in your '''home''' directoryin your Matrix account.<br><br># Issue the following Linux commands (using the ''semicolon '' character "''';'''" to separate <u>each </u> Linux command): <br><span style="color:blue;font-weight:bold;font-family:courier;">cal;pwd;date</span><br><br>Note the from the output as well as the <u>order </u> of how what each of those commands were processedLinux command results.<br><br>
# Issue the following Linux commands: <span style="color:blue;font-weight:bold;font-family:courier;">(cal;pwd;date)</span><br><br>Was there any difference in the output of this command as opposed to the previous command?<br><br>Let's see how grouping affects working with redirection.<br><br>
# Issue the following Linux commands: <span style="color:blue;font-weight:bold;font-family:courier;">cal;pwd;date > output.txt</span><br><br>What happened? Where is the output for the '''date''' command?<br>Why isn't the output for the '''cal''' and '''pwd''' commands are NOT contained in that file?<br><br># Issue a Linux command to view the contents of the file called '''output.txt'''<br><br>What do you notice?<br><br>Let's use '''grouping ''' to make modification to the previous command<br><br># Issue the following Linux commands: <span style="color:blue;font-weight:bold;font-family:courier;">(cal;pwd;date) > output.txt</span><br><br>What did you notice?<br><br># Issue a Linux command to view the contents of the file called '''output.txt'''<br><br>What does ''grouping'' do you notice? What did grouping the three when issuing multiple Linux commands do(separated by a semi-colon ";") that uses redirection?<br><br># Issue the following Linux pipeline command (using \ at the end of most lines):<br><span style="color:blue;font-family:courier;font-weight:bold">echo "This will be split over multiple \<br>lines. Note that the shell will realize \<br>that a pipe requires another command, so \<br>it will automatically go to the next line" |tr '[a-z]' '[A-Z]'</span><br><br>Did the command work? What does is the purpose of issuing a Linux command in this command doway?<br><br># After you complete Complete the Review Questions sections to get additional practice, then work on your '''online assignment 2'''<br>and complete '''section3''' labelled: '''Redirection and Pipes'''.
<br><br>
simulate a quiz:
https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101files/uli101_week5_practice.docx
Your instructor may take-up these questions during class. It is up to the student to attend classes in order to obtain the answers to the following questions. Your instructor will NOT provide these answers in any other form (eg. e-mail, etc).
'''Review Questions:'''
# Write a single Linux command to provide a detailed listing of all files in the '''/binetc''' directory, sending the output to a file called listing.txt in the “'''projects'''” directory (append output to existing file and use a relative pathname)
# Write a single Linux command to redirect the stderr from the command:<br>'''cat a.txt b.txt c.txt''' to a file called '''error.txt''' contained in the “'''assignments'''” directory. (overwrite previous file’s contents and use only relative pathnames)
# Write a single Linux command: '''cat ~/a.txt ~/b.txt ~/c.txt''' and redirect stdout to a file called “good.txt” to the “tests” directory and stderr to a file called “'''bad.txt'''” to the “'''tests'''” directory. (overwrite previous contents for both files and use only relative-to-home pathnames).
# Write a single Linux '''pipeline command''' to display only the first 10 characters of each filename contained in your current directory. Also, there is will be a lot of output, so also pause at each screenful so you can navigate throughout the display contents. Use a relative pathname.
# Create a '''table''' listing each Linux command, useful options that were mentioned in this tutorial for the following Linux commands: '''cut''' , '''tr''' , '''wc''' , and '''tee'''.
_________________________________________________________________________________
Author: Murray Saul
License: LGPL version 3
Link: https://www.gnu.org/licenses/lgpl.html
_________________________________________________________________________________
[[Category:ULI101]]