:* Explain Define the purpose of term '''Regular Expressions'''

:* List various several Linux commands (other than '''grep''' or '''egrep''') that can use regular expressions<br>

|colspan="2" |Course Notes'''Slides:'''<ul><li>Week 9 Lecture 1 Notes:<br>[https://ictwiki.cdot.senecacollege.ca/~murrayuli101/slides/ULI101-9.1.pdf PDF] | [https://wiki.saulcdot.senecacollege.ca/uli101/slides/ULI101-Week99.1.pptx PPTX]</li><li>Week 9 Lecture 2 Notes:<br> [https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-9.2.pdf PDF] | [https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101slides/ULI101-Week99.2.pptx PPTX]<br></li></ul>

| style="padding-left:15px;" |'''Regular Expressions:'''

| style="padding-left:15px;"|'''Linux Commands:'''

|colspan="1" style="padding-left:15px;" width="30%"|'''Brauer Instructional Videos:'''<ul><li>[https://www.youtube.com/watch?v=-2pwLHcvCsU&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=12 Using grep Command with Regular Expressions]</li></ul>

<i>A '''regular expression''' … is a sequence of characters that define a search pattern.  Usually such patterns are used by string searching algorithms for "find" or "find and replace" operations on strings, or for input validation. </i><br>Reference: https://en.wikipedia.org/wiki/Regular_expression ===Regular Expressions vs. Filename Expansion===

<table align="right"><tr valign="top"><td>[[Image:re-1.png|thumb|right|350px|'''Filename expansion symbols''' allow the Linux shell to expand filenames as arguments (referred to as “globbing”).]]</td><td>[[Image:re-2.png|thumb|right|250px|'''Concept''' of matching a simple pattern of text contained within a text file.]]</td></table>In a previous lesson, you learned that '''filename expansion symbols''' allow the Linux shell to expand filenames as arguments (referred to as “globbing”) for file management commands. This is very useful for managing multiple files sharing similar characteristics such as the same file extension.  ''Filename Expansion symbols'' are used to search, edit and manipulate text and are used with Linux file management commands such as '''ls''', '''rm''', '''mv''', '''cp''', '''cat''', '''less''', '''more''', '''head''', '''tail''', '''sort''', '''uniq''', '''cut''', '''tr''', and '''wc'''.<br><br> <i>A '''regular expression''' is a combination of two types of characters: '''literals''' and '''special characters'''.<br>In combination, these characters define a logical pattern. Strings of text can be compared to this pattern<br>to see if they fit the pattern defined by the expressionthere is a match.</i> Reference: https://www.whoishostingthis.com/resources/regex/

[[Image:re-3.png|thumb|right|250px200px|The simplest A '''simple''' ('''literal''') regular expression is a series of letters and numbers, possibly including white space (tabs or space charactersspaces).]]The simplest regular expression is a series of letters and numbers, possibly including white space (tabs or space charactersspaces), that have no special meaning. Such a <br>A '''simple''' ('''literal''') regular expression consists of ``literals''; that is, normal letterscharacters, which used to match only an identical letter in the data being searchedpatterns.<br><br>For example:"This is a Although there are many Linux commands that use regular expression"<br><br><i>When an editor searches for a expressions, the '''literal regular expressiongrep''', it can only score command is a ``hit'' if it finds exactly that sequence useful command to learn how to display matches of patterns of characters in the data it is searchingstrings within text files.</ibr> <br>ReferenceFor example:<span style="color:blue;font-weight: httpbold;font-family://osr507doccourier;">grep Linux document.xinuos.comtxt</en/OSUserG/_Literal_chars_in_regexps.htmlspan><br><br>

===Complex / Extended Regular Expressions=== The problem with using literals or simple regular expressions is that only <u>simple</u> or <u>general</u> patterns are matched.

For example, the pattern “'''theComplex Regular Expressions'''” would be matched for larger word containing that pattern like <br><br>The problem with just using '''theresimple''', ('''theyliteral''', '''either''', '''them''', '''their''', etc.) regular expressions is that only <u>simple<br/u>Another problem is that you may want to search for pattern at a specific location within the string of text (like at the beginning or end)<u>general</u> patterns are matched.

There are other regular expression tools ''Complex Regular Expressions'' use symbols to provide help match text for more <u>precise matches</u> (complex) patterns. These tools <br>The most common complex regular expression symbols are displayed below:<br><br>:'''Anchors: ''' <span style="color:blue;font-family:courier;font-weight:bold;">^</span> , <span style="color:blue;font-family:courier;font-weight:bold;">$</span><br>Match lines the begin (^) or end ($) with a pattern.<br>:'''Single Character:'''complex&nbsp; <span style="color:blue;font-family:courier;font-weight:bold;">.</span><br>Represents a single character that can be any type of character.<br>:'''Character Class:'' and ' <span style="color:blue;font-family:courier;font-weight:bold;">[ ]</span> , <span style="color:blue;font-family:courier;font-weight:bold;">[^ ]</span><br>Represents a single character but with restrictions.<br>:''extended'Zero or More Occurrence:'' regular expressions' <span style="color:blue;font-family:courier;font-weight:bold;">*</span><br>Zero or more occurrences of previous character. <br><br>

:Examples of '''Complex Regular Expressionscomplex regular expressions''' use symbols to help match text for more <u>precise</u> (complex) patterns.<br>The most common complex regular expression symbols are displayed below:

:*'''Anchors: ''' <span styletable align="font-family:courier;font-weight:bold;left">^</span> , <span styletr valign="font-family:courier;font-weight:bold;top">$</spantd><br>Match lines the begin (^) or end ($) with a pattern[[Image:re-4.png|thumb|right|200px|Example of using '''anchors'''.]]<br/td><brtd>[[Image:*re-5.png|thumb|right|175px|Example of matching by '''Single Character:character(s)''' &nbsp; <span style="font-family:courier;font-weight:bold;">.]]</spantd><brtd>Represents a single character that can be any type [[Image:re-6.png|thumb|right|220px|Example of using '''characterclass'''.]]<br/td><brtd>[[Image:*re-7.png|thumb|right|200px|Example of matching '''Character Class:zero or more occurrence of preceding character''' .]]</td><span style="font-family:courier;font-weight:bold;"/tr>[ ]</spantable> , <span style="font-family:courier;font-weight:bold;"br>[^ ]</spanbr><br>Represents a single character but with restrictions.<br><br>:*'''Zero or More Occurrence:''' <span style="font-family:courier;font-weight:bold;"br>*</spanbr><br>Zero or more occurrences of previous character.<br><br>

<table align="left"><tr valign="top"><td>[[Image:re-4.png|thumb|right|220px|Example of using ''Extended Regular Expressions'anchors'''.]]consist of additional special characters to “extend”</tdbr><td>[[Image:re-5the capability of regular expressions.png|thumb|right|200px|Example of matching by You must use the '''character(s)egrep'''.]]</td><td>[[Image:re-6.png|thumb|right|220px|Example of using or '''character class'''.]]</td><td>[[Image:regrep -7.png|thumb|right|200px|Example of matching E'''zero or more occurrence of preceding character'''.]]</td></tr></table><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>commands<br>in order to properly use extended regular expressions.

:*'''RepetitionGroups: {min,max}'''<span style="color:blue;font-family:courier;font-weight:bold;">( )</span><br>Allows you to search for more precise repetitions. Using bracesrepetition for a '''group of characters''', a '''word''', you can specify<br>the or a '''minimumphase''' and.<br>You enclose them within brackets <span style="font-family:courier;font-weight:bold;">( )</or span> to specify a '''maximumgroup''' number of repetitions.

:*'''Groupingor Condition: ( )''' <span style="color:blue;font-family:courier;font-weight:bold;">|</span><br>Perhaps you want Can be used with '''groups''' to search for repetition for match a group variety of characters, a wordcharacter(s), words or a phasephases.<br>You can enclose them within brackets The | symbol is used to separate the variety of character( s) to specify within a ''group''.<br><br>

:*Examples of how to use '''or Condition: |extended regular expressions'''<br>Can be used with grouping to match a variety of character(s), words or phases.<br>The | symbol is used to separate the variety of character(s) within a group.'''egrep''' command are displayed below:<br><br>

Examples <table align="left"><tr valign="top"><td>[[Image:re-8.png|thumb|right|280px|Example of using '''repetition'''.]]</td><td>[[Image:re-9.png|thumb|right|250px|Example of using '''groups'''.]]</td><td>[[Image:re-10.png|thumb|right|250px|Example of how to use these complex regular expressions using '''or''' condition with the '''egrepgroups''' command are displayed below:.]]</td></tr></table><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>

<table align="left"><tr valignINVESTIGATION 1: SIMPLE &amp; COMPLEX REGULAR EXPRESSIONS="top"><td>[[Image:re-8.png|thumb|right|280px|Example of using '''repetition'''.]]</td><td>[[Image:re-9.png|thumb|right|250px|Example of using '''grouping'''.]]</td><td>[[Image:re-10.png|thumb|right|250px|Example of using '''or condition with grouping'''.]]</td></tr></table><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>

<span style=INVESTIGATION 1"color: SIMPLE &ampred; COMPLEX REGULAR EXPRESSIONS=">'''ATTENTION''': This online tutorial will be required to be completed by '''Friday in week 10 by midnight''' to obtain a grade of '''2%''' towards this course</span><br><br>

<br>In this sectioninvestigation, you will learn how to use the '''grep''' command with '''simple and complex regular expressions'''<br>to help search for ''patterns'' contained in text files.

# Issue a Linux command to '''confirm''' you are located in your '''home''' directory.<br><br>The # Issue the following linux Linux command to '''wgetcopy''' command is used a text file to download files ''your'' '''home''' directory from the Internet to your shell.ULI101 home directory:<br>This will be useful to download text files that we will be using for this tutorial.<br><br># Issue the following linux command ('''copy and paste''' to save time):<br><span style="color:bluespan style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https:cp ~uli101//ict.senecacollege.ca/~murray.saul/uli101tutorialfiles/textfile1.txt<~/nowiki></span><br><br># Issue View the contents of the '''lstextfile1.txt''' command to confirm that file using the text file was downloaded'''more''' command see what data is contained in this file.<br><br># View the contents of Although there are several Linux commands that use regular expressions,<br>we will be using the '''textfile1.txt''' file using the '''moregrep''' command and quickly view the contents of for this fileinvestigation.<br>When finished, '''exit''' the more command.<br><br>Although there are several Linux commands that use regular expressions,<br>we will only be using the [[Image:regexps-1.png|thumb|right|250px|Output of '''grep''' command for this section.<br><br>#Issue the following linux pipeline command to match the pattern the within matching simple regular expression "'''textfile1.txtthe'''" (only lowercase). Notice the pattern matches larger words like "'''their''':<br><span style="color:blue;font-weight:bold;font-family:courier;or ">grep '''them'''"the" textfile1.txt | more<br><br>]]# Now, issue Issue the grep linux pipeline following Linux command with to match the pattern '''the '''-iwithin '''textfile1.txt''' option to ignore case sensitively:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -i "the" textfile1.txt | more</span><br><br>What do you notice is different with this pipeline command?Take a few moments to view the output and observe the matched patterns.<br><br>You will notice that # Issue the pattern "grep Linux command with the<span style=" is matched including larger words that contain the pattern font-weight:bold;font-family:courier;"the". You can use the >-w i</span> option with the grep command in order to just match only words for a pattern.ignore case sensitively:<br><br># Issue the following linux pipeline command:<br><span style="color:span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "the" textfile1.txt | more</span><br><br>You should now see only strings of text What do you notice is different when issuing this command?<br><br>You will notice that match the word pattern "'''the'''"theis matched including larger words like "'''.<br>them'''" and "'''their'''".<br>Matching literal or simple regular expressions You can be useful, but are limited in what they can assist issue the '''grep''' command with pattern matching.the <brspan style="font-weight:bold;font-family:courier;">For Example, you may want -w</span> option to search for only match the pattern at as a specific location within '''word'''.<br><br># Issue the string of text (like at the beginning or end of the string).following Linux command:<br><br>There are other regular expression tools to provide more precise matchesspan style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "the" textfile1. These tools are txt</span><br><br>You should now see only strings of text that match the word '''complex''' and '''extendedthe''' (upper or lower case).<br><br>Matching literal or simple regular expressions. We will now look at complex regular expression symbols nowcan be useful, and we will discuss but are '''extended regular expressionslimited'''<br>in what pattens they can match. For example, you may want to<br>search for a pattern located at the '''beginning'Italic text''or '' in 'end''' of the next section of this tutorialstring.<br><br># Issue the following Linux pipeline command:<br>There are other regular expression symbols that provide more '''precise''' search pattern matching.<span style="color:blue;font-weight:bold;font-family:courier;"br>grep -w -i "^the" textfile1.txt | more</span><br><br>The These special characters are known as '''complex'^''and ' symbol is an anchor''extended''' regular expressions symbols. In this case, it only matches the <ubr>word</ubr> "For the" (both upper or lowercase) at the beginning of strings.<br>The remainder of this investigation, we will focus on '''$complex regular expressions''' symbol is used to anchor patterns at the end of strings.and then<br>focus on ''extended regular expressions'' in INVESTIGATION 2.<br># Issue the following Linux pipeline command:<br><span styletable align="right"><tr valign="colortop"><td>[[Image:blue;font-weight:bold;font-family:courier;">grep -w -i "the$" textfile1regexps-2.txt png|thumb|right|280px| more</span>Anchoring regular expressions at the '''beginning''' of text.]]<br/td><brtd>[[Image:regexps-3.png|thumb|right|250px|Anchoring regular expressions at the '''ending''' of text.]]</td>What do you notice?<br/tr><br/table># Issue the following Linux pipeline command to anchor the work "the" simultaneously at the beginning and the end of the string:<:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^the$" textfile1.txt | more</span><br><br>What do you notice?<The '''^''' symbol is referred to as an '''anchor'''.<br>In this case, it only matches<br>Anchoring patterns at both the word "'''the'''" (both upper or lowercase) at the <u>beginning</u> and <u>endingbeginning</u> of strings can greatly assist for more robust search patternsthe string.<br>We will now be demonstrating '''simultaneous anchoring''' with other complex regular expressions symbols.<br><<br># Issue the following Linux command to match strings that begin with 3 characters:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^...-w -i "the$" textfile1.txt | more</span><br><br>What do you notice?The '''$''' symbol is used to anchor patterns at the <u>end</u> of the string.<br><br># Issue the following Linux command to match strings that begin and end with 3 characters:anchor the <bru>word<span style=/u> "color:blue;font-weight:bold;font-family:courier;'''the'''"<br>grep "^...$" textfile1.txt | more'''simultaneously''' at the <u>beginning</spanu> and <u>end<br/u><br>What do you notice?<br><br># Issue the following command to match strings that begin with 3 digits:of the string:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^[0-9][0-9][0-9]the$" textfile1.txt | more</span><br><br># Issue the following command to match strings that end with 3 uppercase letters:What do you notice?<br><br>Anchoring patterns at both the <span style="color:blue;font-weight:bold;font-family:courier;"u>beginning</u> and <u>ending</u>grep "[A-Z][A-Z][A-Z]$" textfile1of strings can greatly assist<br>for more '''precise''' search pattern matching.txt | more</span><br><br># Issue We will now be demonstrate the following command to match strings that consist '''effectiveness''' of only 3 digits:<bru>combining</u><span style="color:blue;font-weight:bold;font-family:courier;"br>grep "^[0-9][0-9][0-9]$" textfile1.txt | more'''anchors''' with <u>other</spanu>complex regular expressions symbols.<br><br>The '<table align="right"><tr valign="top"><td>[[Image:regexps-4.png|thumb|right|280px|Anchoring regular expressions using '''period'*''symbols at the ' complex regular expression symbol is often confused with filename expansion. In other words, it does NOT represent zero or more of '''any characterbeginning''', but zero or or occurrences of the character that comes before the * symbol.text.]]<br/td><brtd># To demonstration, issue the following command to display zero or more occurrences of the letter x[[Image:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "x*" textfile1regexps-5.txt png|thumb| more</span><br><br>You will most likely notice most lines right|250px|Anchoring regular expressions using '''period''' symbols simultaneously at the '''beginning''' and '''ending''' of the file is displayedtext.]]</td><br/tr><br/table># Let's issue a Issue the following Linux command to display match strings that contain more than one occurrence of the letter x'''begin with 3 characters''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "xx*^..." textfile1.txt | more</span><br><br>Why did this workWhat do you notice? Can lines that contain '''less than 3 characters''' be displayed? because the pattern indicates one occurrence of the letter x, followed by zero or MORE occurrences of the letter x.<br><br>If you combine # Issue the complex regular expression symbols .* it will act like zero or more occurrence of any character (like * did in filename expansion).following Linux command to match strings that '''begin <bru>and<br/u># Issue the following command to match strings begin and end with a number with nothing or anything inbetweenend with 3 characters''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9].*[0-9]..$" textfile1.txt | more</span><br><br>Using What do you notice compared to the previous command?<br><br># Issue the following Linux command to match strings that '''simultaneous anchorsbegin with 3 digits''' combined with the .* symbol(s) can help you to refine your search patterns of strings.:<br><br># Issue the following linux pipeline command to display strings that begin with a capital letter, ends with a number, and contains a capital X somewhere inbetweenspan style="color:<br><span style="color:blue;blue;font-weight:bold;font-family:courier;">grep "^[A0-9][0-Z9].*X.*[0-9]$" textfile1.txt | more</span><br><br>Let's look at another series of examples involving What did you notice?<br><br># Issue the following Linux command to match strings that '''filteringend with 3 uppercase letters''' with numbers so only strings containing valid numbers are :<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "[A-Z][A-Z][A-Z]$" textfile1.txt</span><br><br><table align="right"><tr valign="top"><td>[[Image:regexps-6.png|thumb|right|220px|Anchoring '''3 digits''' at the '''beginning''' and '''ending''' of text.]]</td><td>[[Image:regexps-7.png|thumb|right|250px|Anchoring '''3 alpha-numeric characters''' at the '''beginning''' and '''ending''' of text.]]</td></tr></table>What type of strings match this pattern?<br><br># Issue the following Linux command to match strings that '''consist of only 3 digits''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9][0-9][0-9]$" textfile1.txt</span><br><br>What did you notice?<br><br># Issue the following Linux command to match strings that '''consist of only 3 alphanumeric digits''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]$" textfile1.txt</span><br><br>What did you notice?<br><br>The <span style="font-weight:bold;font-family:courier;">"*"</span> complex regular expression symbol is often confused with the "*" '''filename expansion''' symbol.<br>In other words, it does NOT represent zero or more of '''any character''', but zero or more '''occurrences'''<br>of the character that comes '''before''' the <span style="font-weight:bold;font-family:courier;">"*"</span> symbol.<br><br># To demonstrate, issue the following Linux command to display '''zero or more occurrences''' of the letter "'''x'''":<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "x*" textfile1.txt</span><br><br>You will most likely notice most lines of the file is displayed.<br><br># Let's issue a Linux command to display strings that contain '''more than one occurrence''' of the letter "'''x'''":<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "xx*" textfile1.txt</span><br><br>Why did this work? because the pattern indicates one occurrence of the letter "x",<br>followed by '''zero or MORE occurrences''' of the <u>next</u> letter "x".<br><br>If you combine the complex regular expression symbols <span style="font-weight:bold;font-family:courier;">".*"</span> it will act like<br>zero or more occurrences of <u>any</u> character (i.e. like <span style="font-weight:bold;font-family:courier;">"*"</span> did in filename expansion).<br><br># Issue the following Linux command to match strings begin and end with a number with nothing or anything inbetween:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9].*[0-9]$" textfile1.txt</span><br><br>Using '''simultaneous anchors''' combined with the <span style="font-weight:bold;font-family:courier;">".*"</span> symbol(s) can help you to refine your search patterns of strings.<br><br># Issue the following Linux command to display strings that begin with a capital letter,<br>end with a number, and contains a capital X somewhere inbetween:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[A-Z].*X.*[0-9]$" textfile1.txt</span><br><br>Let's look at another series of examples involving searching for strings that only contain '''valid numbers'''.<br>We will use '''pipeline commands''' to both display stdout to the screen and save to files<br>for confirmation of running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br>

# First, issue the following linux Linux command to download copy another data file called '''numbers1.dat''':<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/cp ~murray.saululi101/uli101tutorialfiles/numbers1.dat<~/nowiki>regexps</span><br><br># View the contents of the '''numbers.dat''' file using the '''more''' command and quickly view the contents of this file. <br>You should notice '''valid ''' and '''invalid ''' numbers contained in this file. When finished, exit the more command.<br><br># Issue the following linux pipeline command to display only '''whole ''' numbers(i.e. no '''+''' or '''-''' sign):<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9]*$" numbers1.dat | tee faulty.txt | more</span><br><br>You may have noticed that the command '''does not entirely work'''. You may notice an '''empty line '''<br>(which is NOT a whole number). This occurs since the * regular expression symbol represents <br>ZERO or MORE occurrences of a number. You can use an additional numeric character class <br>with the * regular expression symbol to search for one or more occurrences of a number.<br><br># Issue the following linux Linux pipeline command to display only whole numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9][0-9]*$" numbers1.dat | tee whole.txt | more</span><br><br>You should see that this now works.<br><br># Issue the following linux Linux pipeline command to display whole positive or negative <u>only</u> '''signed''' integers:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-][0-9][0-9]*$" numbers1.dat | tee signed.txt | more</span><br><br>What did you notice?Positive and negative numbers display, not '''unsigned''' numbers.<br><br>[[Image:regexps-8.png|thumb|right|300px|Simultaneous '''anchoring''' of regular expressions using '''character class''' and '''zero or more occurrences''' to display '''signed''' and '''unsigned''' integers.]]# Issue the following linux Linux pipeline command to display only whole numbers (with '''signed''' or without a positive or negative sign)'''unsigned integers''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-]*[0-9][0-9]*$" numbers1.dat | tee all.txt | more</span><br><br>Did this command work?<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/scripts~uli101/week9-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>You can also use the '''grep''' command using ''regular expression'' as a '''filter''' in pipeline commands.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | grep "[0-9].*dat$"</span><br><br>What did this pipeline display?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | grep "[a-z].*txt$"</span><br><br>What did this pipeline display?<br><br> : Although very useful, '''complex''' regular expressions do NOT <u>entirely</u> solve our problem of displaying<br> '''valid''' unsigned and signed numbers (not to mention displaying decimal numbers).<br><br>In the next investigation, you will learn how to use '''extended''' regular expressions that will completely solve this issue.<br>

:Proceed You can proceed to Investigation INVESTIGATION 2.<br>

<br>In this sectioninvestigation, you will learn how to use '''extended regular expressions''' with the '''egrep''' command<br>to help further refine your search when using regular expressionspatterns.

# Issue the following linux pipeline Linux command to download copy another data file called '''numbers2.dat''':<br><span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https://ict.senecacollege.ca/cp ~murray.saululi101/uli101tutorialfiles/numbers2.dat<~/nowiki></span><br><br># View the contents of the '''numbers2.dat''' file using the '''more''' command and quickly view the contents of this file.<br>You should notice ''valid '' and more ''invalid '' numbers contained in this file. When finished, exit the more command.<br><br># Issue the following linux pipeline command to display only whole numbers (with or without a positive or negative sign)[[Image:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-]*[0-9eregexps-1.png|thumb|right|300px|'''Weakness''' of '''complex''' regular expressions that do not '''limit''' the number of '''positive''' or '''negative''' signs.][0-9]*$" numbers2.dat | more</span># Issue the following Linux command to display '''signed''' or '''unsigned integers''':<br><brspan style="color:blue;font-weight:bold;font-family:courier;">You should notice multiple grep "^[+ or - signs are appearing as well. This occurs since you are searching or one or MORE occurrences of a + or - sign]*[0-9][0-9]*$" numbers2.dat</span><br><br>Using You should notice '''extended regular expressionmultiple''' symbols to specify minimum and maximum repetitions '''{min,max}+''' or '''-''' '''signs''' can solve this problem.appear <bru>prior<br/u># Issue the following linux pipeline command (using extended regular expression symbols) to display only whole some numbers (with or without a positive or negative sign):.<br>This occurs since you are searching or one or MORE occurrences of a + or - sign.<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-]br>Using '''extended regular expression''' symbols to specify '''minimum''' and '''maximum''' repetitions: '''{0.1min,max}[0-9]{1,}$" numbers2''' can solve that problem.dat | more</span><br><br># Issue the following Linux command (using extended regular expression symbols)<br>to display '''''NOTE:signed''' most likely, there were or '''NO resultsunsigned integers'''. This is due to the fact that the '''grep command was NOT issued correctly to use extended regular expression symbols'''. You would need to issue either '''grep :<br><span style="color:blue;font-weight:bold;font-E''' (or more simply) issue the '''egrep''' commandfamily:courier;">grep "^[+-]{0,1}[0-9]{1,}$" numbers2. The egrep command works with all regular expression symbols, and should be used in the future instead of the older grep command.<dat</span><br><br># Reissue the above pipeline command using '''egrepNOTE: No output will be displayed! Why?''' instead of <br><br>This is due to the fact that the '''grepcommand was NOT issued correctly to use extended regular expression symbols'':'.<br><span style="color:blue;fontYou would need to issue either '''grep -weight:bold;font-family:courier;">E''', or just issue the '''egrep''' command. The egrep "^[+-]{0command works with<br>'''all''' regular expression symbols,1}[0-9]{1,}$" numbers2.dat | tee better-number1.txt | moreand should be used in the future <u>instead</spanu>of the older grep command.<br><br>You should have noticed that the command worked correctly this time because you used the We will use '''egreppipeline commands''' command.<br>to both display stdout to the screen and save to files<br>for confirmation of running these pipeline commands when run a '''NOTE:checking-script''' In extended regular expressions, later in this investigation.<br><br># Issue the following Linux pipeline command using '''?egrep''' symbol can be used to represent the instead of '''{0,1}grep''' repetition symbols:<br>and the '''<span style="color:blue;font-weight:bold;font-family:courier;">egrep "^[+''' symbol can be used to represent the '''-]{0,1}[0-9]{1,}''' repetition symbols$" numbers2.dat | tee better-number1.txt</span><br><br># Reissue the above pipeline command using [[Image:eregexps-2.png|thumb|right|300px|Using '''egrepextended''' instead regular expression symbols (such as '''repetition''') to refine matches of ''grepsigned'' and ''unsigned'':<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep "^[+-integers.]]?[0-9]+$" numbers2.dat | tee better-number2.txt | more</span><br><br>You should have seen noticed that the same results, but command worked correctly this time because you used the extended regular expression required less typing'''egrep''' command.<br><br># Issue '''NOTE:''' With extended regular expressions, the following linux pipeline command '''?''' symbol can be used to display signed, unsigned, wholerepresent the '''{0, 1}''' repetition symbols and decimal numbers:<brthe '''+''' symbol can be used to represent the '''{1,}''' repetition symbols<br><span style=br># Issue the following Linux pipeline command using the repetition shortcuts <span style="color:blue;font-weight:bold;font-family:courier;">egrep "^[+"</span> and <span style="font-weight:bold;font-]{0,1}[0-9]{1,}[.]{0,1}[0-9]*$family:courier;">"?" numbers2.dat | tee better-number3.txt | more</span>:<br><br># Issue the following Linux command to check that you created those hard links: <br><span span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/scripts/week9egrep "^[+-]?[0-check9]+$" numbers2.dat | tee better-2number2.txt</span><br><br>If you encounter errors, then view You should have seen the feedback to make corrections'''same results''', and then re-run the checking scriptbut less typing was required.<br>If you receive a congratulation message that there are no errors, then proceed with this tutorial.<<br><br>You can also use extended regular expression symbols for # Issue the following Linux pipeline command to display '''signed''', '''groupingunsigned'''. For example, you can search for repetitions of GROUPS of characters'''whole''', and '''decimal''' numbers:<br>(like a word) as opposed to just a single character or a GROUP of numbers as opposed to a single digit.<br<span style="color:blue;font-weight:bold;font-family:courier;"><br># Issue the following linux pipeline command to download another data file called '''wordsegrep "^[+-]{0,1}[0-9]{1,}[.dat''':]{0,1}[0-9]*$" numbers2.dat | tee better-number3.txt</span><br><span style="color:blue;font-weight:bold;font-family:courier;"br>Were all signed and unsigned intergers and decimal numbers displayed?<br>wget <nowiki>https://ict.senecacollege.ca/~murray.saul/uli101/words.dat</nowiki></spanbr># Issue the follwoing command to check that you correctly issued<br><br># View the contents of the those '''numbers2.datLinux pipeline commands''' file using the '''more''' command and quickly view the contents of this file.: <br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week9-check-2</span><br><br>You should notice valid and more invalid numbers contained in this file. When finishedIf you encounter errors, then view the feedback to make corrections, exit and then re-run the more commandchecking script.<br><brIf you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br># Issue the following linux pipeline command to display two or more occurrences of the word "the":You can also use extended regular expression symbols for '''grouping'''.<br>For example, you can search for repetitions of GROUPS of characters (like a word)<span style="color:blue;font-weight:bold;font-family:courier;"br>as opposed to just a single character or a GROUP of numbers as opposed to a single digit.<br>egrep -i "(<br># Issue the){2,}" following linux pipeline command to copy another data file called '''words.dat | tee word-search1.txt more</span>''':<br><br>'''NOTEspan style="color:''' You should NOT see any output due to the fact that a <ublue;font-weight:bold;font-family:courier;">spacecp ~uli101/tutorialfiles/words.dat ~/</uspan><br><br> should be included at # View the end contents of the word "'''thewords.dat'''"file using the '''more''' command and quickly view the contents of this file. Usually words are separated by spaces; therefore<br>Within this file, there were no matches since there were not occurrences you should notice some lines that contain repetitions of "thethe" as opposed to "'''the the'''" (i.e. no space after repetition of the pattern)words. When finished, exit the more command.<br><br># Reissue Issue the previous following linux pipeline command including a space in bracketsto display '''two or more occurrences''' of the word "the":<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep -i "(the ){2,}" words.dat | tee word-search2search1.txt | more</span><br><br>The "|" (or) symbol can be used within '''NOTE: No output is displayed! Why?'''<br><br>This is due to the grouping symbols to allow matching of additional groups of characters.fact that a <bru>Again, it is important to follow the character groupings with the space character<br/u><br># Issue should be included at the following linux pipeline command to search for 2 or more occurrences end of the word "'''the'''" .<ubr>orUsually words are separated by spaces; therefore, there were no matches since there were not occurrences</ubr> the word of "thethe" as opposed to "'''andthe the'''":(i.e. no space after repetition of the pattern).<br><span style="color:bluebr># Reissue the previous pipeline command with the word the followed by a '''space''' within the brackets:<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep -i "(the |and ){2,}" words.dat | tee word-search3search2.txt | more</span><br><br># Issue the following Linux command to check that you created those hard links[[Image: eregexps-3.png|thumb|right|330px|Using '''extended''' regular expression symbols (such as '''grouping''') to refine matches of repetition of '''words''' (as opposed to ''characters'').]]The <br><span style="color:blue;font-weight:bold;font-family:courier;">bash /home/murray.saul/scripts/week9-check-3</span><br>style="font-weight:bold;font-family:courier;">"|"<br/span>If you encounter errors, then view (or) symbol (same symbol as "pipe") can be used within the feedback grouping symbols to make correctionsallow matching of additional groups of characters.<br>Again, and then reit is important to follow the character groupings with the space character<br><br># Issue the following linux pipeline command to search for '''two or more occurrences''' of the word "'''the '''" <u>or</u> '''two or more occurrences''' of the word "'''and '''":<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep -run the checking script.<br>If you receive a congratulation message that there are no errors, then proceed with i "(the |and ){2,}" words.dat | tee word-search3.txt</span><br><br># Issue the following Linux command to check that you correctly issued<br>those ''Linux pipeline commands'' using the '''tee''' command to create those text files:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week9-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>Let's issue a Linux '''pipeline''' command using the '''egrep''' command as a '''filter'''<br>using <u>both</u> '''complex''' and '''extended''' regular expressions.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | egrep "[a-z]{1,}.*[0-9]"</span><br><br>What did this Linux pipeline command display?<br><br>: The '''grep''' and '''egrep''' Linux commands are NOT the only Linux commands that use regular expressions.<br>In the next investigation, you will apply regular expressions to a number of Linux commands<br>that you already learned in this tutorialcourse.<br><br>

:Proceed You can proceed to Investigation INVESTIGATION 3<br><br>

=INVESTIGATION 3: OTHER COMMANDS THAT USE USING REGULAR EXPRESSIONS =<br>In this sectioninvestigation, you will see how regular expressions can be used with other Linux utilities commands other than '''grep''' or '''egrep'''that can use regular expressions.

# Make certain that you are located in your '''~/regexps''' directory on your ''Matrix'' account.<br><br># Let's look at using regular expressions with the '''man ''' command.<br>Issue the following linux command :<br><span style="color:blue;font-weight:bold;font-family:courier;">man ls</span><br><br>[[Image:other-re-1.png|thumb|right|300px|Entering '''/sort''' in the '''man''' command can search for the string "'''sort'''".]]# We want to search for an option that can sort the file listing.<br>Type the following regular expression below and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">/sort</span><br><br>'''FYI:''' The '''grep''' and '''egrep''' linux Linux commands contain the regular expressions within quotes,<br>but '''most ''' other Linux commands specify regular expressions using forward slashes<br>'''forward slashes''' (e.g. '''<span style="font-weight:bold;font-family:courier;">/regular expression</''' span> &nbsp; or '''&nbsp; <span style="font-weight:bold;font-family:courier;">/regular expression'''/</span>).<br><br># Scroll throughout the man pages for the ls command to view matches for the pattern "'''sort'''"<br>(You can press '''SPACE''' and or key combination '''&lt;ALT&gt;&lt;alt-b&gt;''' to move forward and backwards per page one screen respectively).<br><br># Press the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span> to '''exit ''' the ''man '' pages for '''ls'''.<br><br>#Let's use regular expressions with the '''moreless''' command.<br><br># Issue the following linux Linux command to view the contents of the copy another data file called '''textfile1large-file.txt''' (downloaded in a previous section):<br><span style="color:blue;font-weight:bold;font-family:courier;">more textfile1cp ~uli101/tutorialfiles/large-file.txt~/</span><br><br>#We want to search for a pattern [[Image:other-re-2.png|thumb|right|300px|Entering '''/uli101''' in the '''less''' command can display all matches of "'''uli101''' within this " throughout the text file.<br>Type ]]# Issue the following regular expression and press ENTERLinux command to view the contents of the '''large-file.txt''':<br><span style="color:blue;font-weight:bold;font-family:courier;">/uli101less large-file.txt</span><br><br>What did you notice?<br><br>#Search We want to search for the next occurrence of the a pattern '''uli101''' by '''re-typing''' within this text file.<br>Type the following regular expression and pressing press ENTER:<br><span style="color:blue;font-weight:bold;font-family:courier;">/uli101</span><br><br>you You should now see the '''second occurrence''' of this pattern within "uli101" throughout the text file.<br><br># Press the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span> to exit the '''moreless''' command.<br><br>#Try the same search techniques with the '''more''' command.<br><br>Does it work the same for the ''less'' command?<br><br>[[Image:other-re-3.png|thumb|right|300px|Entering '''/uli101''' in the '''vi''' command can search for the string "'''uli101'''".]]Let's learn how to perform a simple '''search and replace''' within the '''vi''' utility <br>by using regular expressions.<br><br># Issue the following linux Linux command to edit the '''textfile1large-file.txt''' file:<br><span style="color:blue;font-weight:bold;font-family:courier;">vi textfile1large-file.txt</span><br><br>Let's first perform a simple search within this text file.<br><br># Press the '''ESC''' key to make certain you are in '''COMMAND''' mode.<br><br># Type the following and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">/uli101</span><br><br>You should move to the '''first occurrence''' of notice the pattern: "'''uli101'''" highlighted for ALL occurrences in this text file.<br><br>Let's '''search ''' for the '''uli101''' pattern, but and '''replace ''' it in capitals (i.e '''ULI101''').<br><br>In vi, in order to perform and issue a command, you need to go into last line mode, and enter '''LAST LINE''' MODE then issue a command to apply to the entire text file, followed by .<br>Let's issue a regular expression command from '''LAST LINE''' MODE to search for and a regular expression replace '''uli101''' to replace (i.e. '''/search/replace/ULI101''').<br><br>[[Image:other-re-4.png|thumb|right|500px|In l'''ast line''' MODE in the '''vi''' text editor, issuing a command using regular expressions to convert '''uli101''' to '''ULI101'''.]]# Type Making certain that you are '''COMMAND''' MODE in vi,<br>type the following and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">:%s/uli101/ULI101/g</span><br><br>You should have noticed that the first occurrence of uli101 has been changed to ULI101.<br><br># Navigate throughout the text file to see if the other occurrences have been replaced.<br><br>You should notice they haven't for ''NOTE:''' The letter '''g''' after the other two occurrences. In order to replace for ALL occurrences, you need to add the letter g (meaning regular expression represents "'''global'''") at the end and will replace ALL occurrences of uli101 in the last forward slash text document (e.g /'''search/replace/g'''as opposed to replacing the first occurrence for every line).<br><br># Making certain that you are command mode in vi, type Type the following (in uppercase letters) and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">:%s/uli101/ULI101/g</span><br><br>You should notice the pattern "'''ULI101'''" highlighted for ALL occurrences in this text file.<br><br># Navigate throughout the text file to confirm that ALL occurrences of '''uli101 ''' have been <u>replaced </u> with '''ULI101'''.<br><br># Save changes to your vi editing session and exit by typing the following and pressing ENTER:<br><span style="color:blue;font-weight:bold;font-family:courier;">:wxx</span><br><br>: After you complete the Review Questions sections to get additional practice, then work on your<br>'''online assignment 3'''.<br><br>

https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101files/uli101_command_practice_9a.docx

Note the contents from the following tab-delimited file called '''~murray.saul/uli101/cars''':

1. <span style="font-family:courier;font-weight:bold">grep plym ~murray.saul/uli101/cars</span><br>2. <span style="font-family:courier;font-weight:bold">grep -i fury ~murray.saul/uli101/cars</span><br>3. <span style="font-family:courier;font-weight:bold">grep “^[m-z]” ~murray.saul/uli101/cars</span><br>4. <span style="font-family:courier;font-weight:bold">grep -i “^[m-z]” ~murray.saul/uli101/cars</span><br>5. <span style="font-family:courier;font-weight:bold">grep “3$” ~murray.saul/uli101/cars</span><br>6. <span style="font-family:courier;font-weight:bold">grep -i “c.*5$” ~murray.saul/uli101/cars</span><br>

https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101files/uli101_command_practice_9b.docx

Note the contents from the following tab-delimited file called '''~murray.saul/uli101/numbers.txt''':

1. <span style="font-family:courier;font-weight:bold">grep "^[-+]" ~murray.saul/uli101/numbers.txt</span><br>2. <span style="font-family:courier;font-weight:bold">grep "^[-+]*.[0-9]" ~murray.saul/uli101/numbers.txt</span><br>3. <span style="font-family:courier;font-weight:bold">grep "^[+-]?[0-9]" ~murray.saul/uli101/numbers.txt</span><br> &nbsp; &nbsp;(Why?)<br>4. <span style="font-family:courier;font-weight:bold">egrep "^[+-]?[0-9]" ~murray.saul/uli101/numbers.txt</span><br>5. <span style="font-family:courier;font-weight:bold">egrep "^[+-]?[0-9]+$" ~murray.saul/uli101/numbers.txt</span><br>6. <span style="font-family:courier;font-weight:bold">egrep "^[+-]?[0-9]+[.]?[0-9]+$" ~murray.saul/uli101/numbers.txt</span><br>

_________________________________________________________________________________ Author: Murray Saul License: LGPL version 3Link: https://www.gnu.org/licenses/lgpl.html _________________________________________________________________________________