(The special Bourne variable "IFS" contains the characters used to "break up" the line. How do I find all files that contain string A but do NOT contain string B on linux using bash?. Based on my Bash experience, I've written Bash 101 Hacks eBook that contains 101 practical examples on both Bash command line and shell scripting. The syntax of these conditions can seem a bit daunting to learn and use. – AFH Sep 26 '14 at 11:27. 03/30/2017; 16 minutes to read +7; In this article. This is the second part of the Bash One-Liners Explained article series. This file contains the feeds of two different websites. To split string in Bash scripting with single character or set of single character delimiters, set IFS(Internal Field Separator) to the delimiter(s) and parse the string to array. (3) to do complex replacement in a text. However, the post should not be specific to another shell. Regular expression tester with syntax highlighting, PHP / PCRE & JS Support, contextual help, cheat sheet, reference, and searchable community patterns. A directory is a file the solo job of which is to store the file names and the related information. Different Regular Expression Engines A regular expression "engine" is a piece of software that can process regular expressions, trying to match the pattern to the given string. ie: VAR="hello". The matches are assigned to an array variable BASH_REMATCH. If you're interested in learning more about character classes and other regex features, I personally have always found regular-expressions. NET, the regex alternate regular expressions module for Python captures 123 to Group 1. Search package contents for a grep basic regular expression pattern x86 x86_64 x86_64. Update pots (including getting rid of SVN) 2018-09-16 21:52 Regina Obe * [r16815] Prepping for 2. If it sits between sharp brackets, it is an HTML tag. Wildcards are characters that can be used to substitute for any other character or characters. I am trying to write a bash script that contains a function so when given a. But from Version 3 of Bash we can use a regular expression without using grep or sed. Great Practical Ideas (GPI) is a course for first-year CS students at Carnegie Mellon University. Thanks in advance. I'll use only the best bash practices, various bash idioms and tricks. One can extract the digits or. Regular Expressions A regular expression is a compact way of describing complex patterns in text. When more than one match is found, Select-string still emits only one MatchInfo object for the line, but the Matches property of the object contains all of the matches. Examples have been provided for Bash Split String operation. Strangely one of the easiest and most portable ways to check for "not contains" in sh is to use the case statement. Regular expressions do not interpret any meaning from the search pattern. The easiest way to check this in python is to use regular expressions. Some, or much, tweaking may be needed to make them work on other Unix systems. 36, for Bash version 3. The result will be sent to stdout (normally the console) but you can also add '> capture' to the end of the line above so that sed sends the output to the file 'capture'. I'm trying to strip an xml string removing every tag in it. You can use wildcard character [crayon-5dbc0ca00bfd3152987516-i/] to find if a string contains a substring in a bash script. If you wanted to eliminate "abc" from the output, you must expand the regular expression to match the rest of the line and explicitly exclude part of the expression using "(", ")" and "\1", which is the next topic. From BASH version 3 there is an inbuilt regex operator( =~ ) which will help us to solve this problem If you are new to regular expressions please click here Below are the types of regular expressions we have and we will go with each and every regexp with an example. Normally if one of the commands executed by a shell script fails it set an exit code different from 0, but the script will not stop. Raw Python strings. bash split string into array. It returns 0 (success) if the regular expression matches the string, otherwise it returns 1 (failure). For a brief introduction, see. The term wildcard or wild card was originally used in card games to describe a card that can be assigned any value that its holder desires. When the replacement flag is provided, all occurrences will be replaced. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized. English and bash are not my first language, please correct me anytime, thank you. Returns an element instance. The most recent version of the Cygwin DLL is 3. In this article let us review the bash case command with 5 practical examples. Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript Regular Reg Expressions Ex 101. This is the Bash FAQ, version 3. Simply put: \b allows you to perform a "whole words only" search using a regular expression in the form of \b word \b. Show the preceding line that contains the function name of the match, unless the matching line is a function name itself. In this article, we will show you several ways to check if a string contains a substring. fi, bash substring, BourneShell substring, echo usage, pdf files, regular expressions, shell Substring, string comparison Cool Linux penguin shirt. A regular expression, or regexp, is a way of describing a set of strings. Based on my Bash experience, I’ve written Bash 101 Hacks eBook that contains 101 practical examples on both Bash command line and shell scripting. Bash and regular expressions 1. For further help, type "h". To scan ahead to find a string pattern, type "/" and enter a regular expression to match. All scripts are released under the GPL license. They are numeric strings—therefore both have the strnum attribute, dictating a numeric comparison. Check destinations of a list of links in a document for a string; Check if a string ends with another string; Determine if a Sequence is in another sequence in Python : solution 1; If a 'bin' exists in the user home, then add that to the PATH. They are all Linux shell scripts and need the Bash shell and GNU commands to run (standard on any Linux system). Pexpect version 4. Re's are typically used to identify and manipulate specific pieces of data. Bash has its own regular expression engine since version 3. In JavaScript, regular expressions are also objects. They allow us to create a pattern. It's functionality is similar to the grep command on Linux OS. If you try to mconcat an Empty List, bc of the Identity function, f(x) = x, you’ll just get back an empty list! It totally knows. One of the most used feature is to match two or more, multiple string, patterns or regex. If the string contains characters other than the accepted characters above simply exit 1. This is the second part of the Bash One-Liners Explained article series. All the files, whether ordinary, special, or directory, are contained in directories. (The special Bourne variable "IFS" contains the characters used to "break up" the line. Hi yall, i've been searching and testing for a while, but can't find a way to replace all instances of a regex substring in a string, just with bash. #!/bin/bash # substring-extraction. Because you tagged your question as bash in addition to shell, there is another solution beside grep:. It can be used to test a variable against set of patterns. single space a string in javascript. In order to successfully work with the Linux sed editor and the awk command in your shell scripts, you have to understand regular expressions or in short regex. The reason is that it contains a capital T as opposed to lowercase which is what the regular expression was searching for. Substrings matched by parenthesized subexpressions within the regular expression are saved in the array variable BASH_REMATCH. These usually take the form of comparing one variable against another or one variable against a string of text or simply comparing text against text. Examples have been provided for Bash Split String operation. Regular Expressions. To split string in Bash with multiple character delimiter use Parameter Expansions. The syntax of these conditions can seem a bit daunting to learn and use. It parses each line of a text file for a particular string and replaces it with another string. , not a fg %? string # brings job whose command contains string:. Strings can be placed either between single quotes ' or double quotes " and they have slightly different behavior. Their names are matched by this regular expression: Find(All)?(String)?(Submatch)?(Index)? If 'All' is present, the routine matches successive non-overlapping matches of the entire expression. A walk-through on how a Key-Value pair can be parsed using a PERL-compatible regex engine This Tip demonstrates a solution using Qt. Return Value If the length of the resulting C string, including the terminating null-character, doesn't exceed maxsize, the function returns the total number of characters copied to ptr (not including the terminating null-character). We will also learn about this in Arithmetic Operations topic. If you try to mconcat an Empty List, bc of the Identity function, f(x) = x, you’ll just get back an empty list! It totally knows. The main uses for Regular Expressions (REs) are text searches and string manipulation. It can be used to test a variable against set of patterns. Sometimes this is not what you need. Install Cygwin by running setup-x86_64. ElementTree. Certain commands and utilities commonly used in scripts, such as grep, expr, sed and awk, interpret and use REs. The status of a command/function is stored in the bash variable "$?". and the tool i am using is pcregrep so that i can get compatibility with perl's regular expressions for a sample data like this, i am trying to grab (6 Replies). Conditional expressions are used by the [[compound command and the test and [builtin commands. If we try to even things up a bit by making the initial string longer, we find practically the same times for the version using tr, but about 0. Related Searches to - linux - linux tutorial - How to compare two string variables in an 'if' statement in Bash linux red hat debian opensuse ubuntu arch linux mandrake get link linux computer linux pc linux server linux desktop learn linux red hat linux red hat enterprise linux linux software linux tutorial linux operating system suse linux linux download linux os linux ubuntu vmware linux. Bash expression is the combination of operators, features, or values used to form a bash conditional statement. com Jeff ,May 8 at 18:30 Given a filename in the form someletters_12345_moreleters. 3 2017-04-25 08:20 Regina Obe * [r15368] regress/subdivide. Regular expressions, that defines a pattern in a string, are used by many programs such as grep, sed, awk, vi, emacs etc. A walk-through on how a Key-Value pair can be parsed using a PERL-compatible regex engine This Tip demonstrates a solution using Qt. Contains method in a C# application in a case-insensitive way: as a matter of fact, there isn't a built-in overload method accepting a StringComparison options object, hence is not possible to do that. Think of a function as a small script within a script. An RE matches a single character or a set of characters -- a string or a part of a string. While there is no portable regular expression support built into the shell itself, shell programs rely heavily on external utilities, many of which use regular expressions. If grep is made to match several strings, all of the matches will be colored, one exception is the regex ^ (match beginning of every line), the beginning of a line has no length so will not be coloued. For example, in the word "frog" the letter "f" is in position 0, the "r" in position 1, the "o" in 2 and the "g" in 3. the right string is considered as a regular. There are also another IDE's available next to Eclipse, e. How to Split String with a Delimiter in Bash Script Written by Rahul, Updated on November 17, 2017. Let us see an example below. How do I do string manipulations in bash? Bash can do string operations. Think of a function as a small script within a script. The regex engine starts at the first token in the regex, G, and at the first character in the string, S. [00:00] leave [00:01] jbsoum: right click your panel, choose "add to panel". match(regex, string). In this tutorial we will look different examples about these features. If statements (and, closely related, case statements) allow us to make decisions in our Bash scripts. Bash is a big program, and the bulky man page can hide some gems. 3 and Apache2. The term wildcard or wild card was originally used in card games to describe a card that can be assigned any value that its holder desires. regular expressions with whatever data you can access using the application or programming language you are working with. For normal text (not markup), there are no special characters except < and &: just make sure your XML Declaration refers to the correct encoding scheme for the language and/or writing system you want to use, and that your computer correctly stores the file using that encoding scheme. Hi yall, i've been searching and testing for a while, but can't find a way to replace all instances of a regex substring in a string, just with bash. split REGEX, STRING, LIMIT where LIMIT is a positive number. Write a Bash script so that it receives arguments that are specified when the script is called from the command line. In PowerGREP and EditPad Pro, \b and \B are Perl-style word boundaries, while \y, \Y, \m and \M are Tcl-style word boundaries. If you’re looking for the exact match on the whole string as in your example, you can use [code bash]==[/code]: [code bash] # matches "count" only if [[ ";$tmp". Most of us are familiar with searching for a word within a file, but regular expressions allow us to search for these with more flexibility, particularly in the context of genomics. Most characters are ordinary: they stand for themselves in a pattern, and match the corresponding characters in the subject. bash how to trim string. Ask Question Asked 5 years, 2 months ago. One can test that a bash variable starts with a string or character in bash efficiently using any one of the following. Most often in modern languages this is a quoted sequence of characters (formally "bracketed delimiters"), as in x = "foo", where "foo" is a string literal with value foo – the quotes are not part of the value, and one must use a method. We can use it in control structure to produce search based result. Bash has its own regular expression engine since version 3. Some, or much, tweaking may be needed to make them work on other Unix systems. The matches are assigned to an array variable BASH_REMATCH. The following examples will pass the regular expression, but are all invalid dates: 20180231, 20190229, 20190431. 4 Bash Conditional Expressions. These patterns are used with the exec and test methods of RegExp, and with the match, matchAll, replace, search, and split methods of String. Example-1: String Comparison using "==" operators. sh: Add text at beginning of file. If n < 0, there is no limit on the number of replacements. biz Introduction to BASH Programming @ Tldp. Different Regular Expression Engines A regular expression “engine” is a piece of software that can process regular expressions, trying to match the pattern to the given string. By default the matched text will be colored red. Strings can be placed either between single quotes ' or double quotes " and they have slightly different behavior. Regular expressions are a powerful & flexible way of searching for text strings amongst a large document or file. Ksh has it's own regular expressions. The result will be sent to stdout (normally the console) but you can also add '> capture' to the end of the line above so that sed sends the output to the file 'capture'. Welcome to the most active Linux Forum on the web. How do I return a string (or large number, or negative number) from a function? "return" only lets me give a number from 0 to 255. (I know this regex has a lot of shortcomings, but I'm still trying to learn them) isAlpha='^*$'However, when I bring this over to BASH it doesn't allow me to enter spaces. In this case a glob can be escaped with a preceding \ in order for a literal match. To fully utilize the power of shell scripting, you need to master Regular Expressions. Reversing that string, Group 1 contains 123. is this possible?. The match function searches the string, string, for the longest, leftmost substring matched by the regular expression, regexp. The script contains a jsonval function which operates on two variables, json and prop. It covers topics relating to basic terminal usage and general Unix skills, such as file systems and navigation, bash scripting, Unix text editors (i. CAVEAT: This is one of the few platform dependent bash features. com One of the most common operations when working with strings in Bash is to determine whether or not a string contains another string. In order to successfully work with the Linux sed editor and the awk command in your shell scripts, you have to understand regular expressions or in short regex. Bash - Extract string from string using RegEx in the Stackoverflow. However, based on operations, Bash might convert them to a suitable data type on the fly. An RE matches a single character or a set of characters -- a string or a part of a string. However, the man page is not very clear. @magnetikonline Thank you yes I found where it is explained that if we have shellopt extglob on, then we have a regex-like power but not a BASH_REMATCH or sed extended regex and \1 \2 etc to use in the right hand of ${string/x(y)x/z\1z/}. It returns 0 (success) if the regular expression matches the string, otherwise it returns 1 (failure). I don't find how to match (matching any. (3) to do complex replacement in a text. Regular expressions do not interpret any meaning from the search pattern. If regex is omitted, then FS is used. Some, or much, tweaking may be needed to make them work on other Unix systems. Ksh has it's own regular expressions. Sed replaces the string 'to_be_replaced' with the string 'replaced' and reads from the /tmp/dummy file. An example is as follows: echo "it's a regular file" fi else. If you're looking for the exact match on the whole string as in your example, you can use [code bash]==[/code]: [code bash] # matches "count" only if [[ ";$tmp". You can also use the grep command to search for targets that are defined as patterns by using regular expressions. The contains() method is helpful to find a char-sequence in the string. Usually such patterns are used by string searching algorithms for "find" or "find and replace" operations on strings, or for input validation. However, the regex engine studied the entire regular expression before starting. In addition to doing simple matching, bash regular expressions support sub-patterns surrounded by parenthesis for capturing parts of the match. The status of a command/function is stored in the bash variable "$?". Comparing Strings using "if" Testing Strings. The word "Regular expression" is a mouthful, so you will usually find the term abbreviated as "regex" or "regexp". Write a Bash script so that it receives arguments that are specified when the script is called from the command line. We will also learn about this in Arithmetic Operations topic. Regular expressions, while different from shell patterns, are crucial to most effective shell scripting. The pattern is typically a Regexp; if given as a String, any regular expression metacharacters it contains will be interpreted literally, e. Select-String can display all the text matches or stop after the first match in each input file. Brief: This example will help you to check if one string contains another substring in a bash script. Each expression can contain characters, metacharacters, operators, tokens, and flags that specify patterns to match in str. If the paragraph contains the string "AX. Match string not containing string Check if a string only contains numbers Regex Tester. #!/bin/bash # substring-extraction. As a trivial example, the pattern The quick brown fox matches a portion of a subject string that is identical to itself. Shell script to print contains of file from given line number to next given number of lines Shell script to say Good morning/Afternoon/Evening as you log in to system Shell script to find whether entered year is Leap or not Sort the given five number in ascending order (use of array) Command line (args) handling:. For all the examples below we will use sentence I am 999 years old. (3) to do complex replacement in a text. Refer to our earlier article on bash { } expansion. 0, using the =~ operator, just like Perl. BASH Scripting aanndd RREEGGEEXX bbaassiiccss FFrreeddLLUUGG HHooww ttoo ddeemmyyssttiiffyy BBAASSHH aanndd RREEGGEEXX Peter Larsen September 27, 2014 Sr. The syntax of these conditions can seem a bit daunting to learn and use. Bash is a big program, and the bulky man page can hide some gems. However, the regex engine studied the entire regular expression before starting. I would like to make a script that deletes a directory with rmdir after confirming with a password using read to set the variable. When the script is passed the name of a twitter user it attempts to download the user's profile picture. Works great. The result will be sent to stdout (normally the console) but you can also add '> capture' to the end of the line above so that sed sends the output to the file 'capture'. 36, for Bash version 3. 0 since the release of bash-4. Your question is confusing: you can either have an exact match (stings are identical) or you can have a regex match (string matches the template in a regular expression). Regular expressions are patterns used to match character combinations in strings. For example, in the word "frog" the letter "f" is in position 0, the "r" in position 1, the "o" in 2 and the "g" in 3. bash man page-- search for the =~ operator to see how it works. Reversing that string, Group 1 contains 123. Introducing Regular Expressions. This program is meant to demonstrate the use of the Regex. * (zero or more of any character). Regular Expressions. Unix uses a hierarchical structure. tostring (element, encoding="us-ascii", method="xml") ¶ Generates a string representation of an XML element, including all subelements. Both parameters are case-normalized using os. It's a small chunk of code which you may call multiple times within your script. So far, we have only used very simple search patterns, like /gold/, but you will now learn advanced search patterns. A string either matches a regular expression or it doesn't - there is no approximate match. A private key, usually named id_rsa. Extended Regular Expressions. However, that decision is not determined by whether or not the progr. One of the most common operations when working with strings in Bash is to determine whether or not a string contains another string. Bash has its own regular expression engine since version 3. In the above example, we have declared a few variables with different data types. This file contains the feeds of two different websites. The regular expression itself can be used with any PERL-compatible regex engine. How can I extract the "test" string and store into a shell variable? A substring is nothing but a string is a string that occurs "in". All data in Awk are regarded as strings, but if that string also happens to represent a number, numeric operations can be performed on it. This lesson starts with the basics, and gradually builds to cover more advanced techniques. If you put characters between single quotes ', then almost all the characters, except the single-quote itself ', are interpreted as they are written in the code. In addition to doing simple matching, bash regular expressions support sub-patterns surrounded by parenthesis for capturing parts of the match. This is the second part of the Bash One-Liners Explained article series. Comparing Strings. If you stumbled upon this post it probably means that you're trying to use the String. Substitutions are language elements that are recognized only within replacement patterns. I would like to make a script that deletes a directory with rmdir after confirming with a password using read to set the variable. If we try to even things up a bit by making the initial string longer, we find practically the same times for the version using tr, but about 0. How to Check if a String Contains a Substring in Bash Linuxize. The longest possible string that matches this search pattern in a paragraph is always found. Match anywhere: By default, a regular expression matches a substring anywhere inside the string to be searched. By default, sed reads the file line by line and changes only the first occurrence of the SEARCH_REGEX on a line. Comparison operators are operators that compare values and return true or false. This will save us a lot of time and reduce the number of lines of a script we write. Since there are many engines for regex, we will use the shell regex and see the bash power in working with regex. I'm using bash substitution to do so, but apparently I missed something about what is a regex for bash. #!/bin/bash # prepend. In this tutorial on Bash scripting, we are going to learn to do comparisons. Using separate matches against shorter strings, or using arrays of strings instead of a single long string, may be faster. To split string in Bash with multiple character delimiter use Parameter Expansions. Features of Regular Expression. Another Bash 3 feature is an improved brace expansion operator:. findstr pattern filename For example, to search for the string ‘Windows’ in the text file CLItips. biz Bash Shell: Find Out If a Variable Is Set or Not; Bash shell find out if a variable has NULL value OR not; Bash Shell Find Out If a Variable Is Empty Or Not; Bash Shell Count Number of Characters In a String or Word; Bash check if string starts with character such as # Use BASH nullglob To Verify *. The regular expression itself can be used with any PERL-compatible regex engine. 3 for more information. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized. if a subString Present in a String; if a string contains another string; PHP - How to check if string contains substring PHP; if a string contains another string; Determine if a Sequence is in another sequence in Python : solution 1; If a 'bin' exists in the user home, then add that to the PATH. How to Split String with a Delimiter in Bash Script Written by Rahul, Updated on November 17, 2017. Essentially, Bash variables are character strings, but, depending on context, Bash permits integer operations and comparisons on variables. It can be used to test a variable against set of patterns. The case construct in bash shell allows us to test strings against patterns that can contain wild card characters. A "regular expression" is a text string that describes a particular search pattern. As you already know, Awk goes line-by-line through a file, and for each line that matches the search pattern, it executes a block of statements. Just to warm up. The match function searches the string, string, for the longest, leftmost substring matched by the regular expression, regexp. It's functionality is similar to the grep command on Linux OS. One area where it's quite capable, which I only recently dug into, is string. Shell script to print contains of file from given line number to next given number of lines Shell script to say Good morning/Afternoon/Evening as you log in to system Shell script to find whether entered year is Leap or not Sort the given five number in ascending order (use of array) Command line (args) handling:. The -n operator checks whether the string is not null. These special characters, called metacharacters, also have special meaning to the system. 36, for Bash version 3. -AllMatches Search for more than one match in each line of text. Tags: Bash, linux, match, matching, pattern, regex, regular expressions, sh, string, substring 9 There are a few ways to find out if a string contains a substring using bash. The main uses for Regular Expressions (REs) are text searches and string manipulation. ) If the first search string is a valid regular expression that contains at least one un-escaped meta-character, then all search strings are treated as regular expressions. However, based on operations, Bash might convert them to a suitable data type on the fly. These usually take the form of comparing one variable against another or one variable against a string of text or simply comparing text against text. When comparing strings in Bash you can use the following operators:. JSON (JavaScript Object Notation) is a lightweight data-interchange format. If regex solution. Your question is confusing: you can either have an exact match (stings are identical) or you can have a regex match (string matches the template in a regular expression). In some cases Bash returns true if the given string "contains" the pattern, whereas this library returns true if the string is an exact match for the pattern. Without this parameter, Select-String will find only the first match in each line. Testing strings in BASH If this is your first visit, be sure to check out the FAQ by clicking the link above. Strangely one of the easiest and most portable ways to check for "not contains" in sh is to use the case statement. The 'natural' name of this doesn't seem to fit its use and common sense on how to think about using this. At least one upper case letter In addition to checking if the upper case version of the string equals to itself, we might want to make sure that there is at least one upper case letter. It parses each line of a text file for a particular string and replaces it with another string. These patterns are used with the exec and test methods of RegExp, and with the match, matchAll, replace, search, and split methods of String. In a 3-full-lines string, like hello\nworld\nOK\n (which you wouldn't be able to obtain with command substitution as command substitution strips all trailing newline characters), the $ would match after the \n, so OK$ wouldn't match on it. If n < 0, there is no limit on the number of replacements. ) now take file system ACLs into account on file systems that support them. # Awk numbers first character of string as '1'. Hey all, I have a very simple regular expression that I use when I want to allow only letters with spaces. There is no built-in comparison function to check equality of two string values in bash like other standard programming language. sed uses regular expressions, such as. All data in Awk are regarded as strings, but if that string also happens to represent a number, numeric operations can be performed on it. The regular expression itself can be used with any PERL-compatible regex engine. Hey all, I have a very simple regular expression that I use when I want to allow only letters with spaces. Bash acquired in-process regular expressions in version 3. How can this be done ? I tried using sed/grep/awk/sort but I can't find the perfect combination. Different Regular Expression Engines A regular expression “engine” is a piece of software that can process regular expressions, trying to match the pattern to the given string. Sun Solaris 10 GNU Bash through 4. This file contains the feeds of two different websites. They allow us to decide whether or not to run a piece of code. It enable you to match several values against one variable. Examples have been provided for Bash Split String operation. Ksh has it's own regular expressions. Great Practical Ideas (GPI) is a course for first-year CS students at Carnegie Mellon University. Single quoted strings. f can be fetched by: ?44. As always, the manual page (doc/bash. array of strings. In the following script, two string variables, strval1 and. c, /trunk/liblwgeom/lwgeodetic_tree. Regular expression tester. (Remember that is used to delimit search strings. - You don't need as much quoting with double brackets as you do with singles, particularly the doubles will work if a nonquoted variable to be tested is empty or contains spaces. But Bash does not have a type system, it can only save string values. The regular expression itself can be used with any PERL-compatible regex engine. Regex Tester isn't optimized for mobile. Sed replaces the string 'to_be_replaced' with the string 'replaced' and reads from the /tmp/dummy file. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. That is when Linux utilities such as grep or egrep can help. Regular expressions, while different from shell patterns, are crucial to most effective shell scripting. It is easier to read and write. Learn about simple string matching, character sets, 'OR' expressions, dealing with blank lines, and reformatting existing data, all with regular expressions. Clearly, we need a really big string to measure bash's speed accurately. (I know this regex has a lot of shortcomings, but I'm still trying to learn them) isAlpha='^*$'However, when I bring this over to BASH it doesn't allow me to enter spaces.