Beginners - Learning Regular Expressions For Programmers

Explore how regular expressions use metacharacters, including brackets for grouping and ranges, negation with the caret, and anchors at string start and end with grep.

Explore metacharacters called quantifiers in regular expressions, including the question mark, star, and plus, using grep with extended regex to match optional characters and digit or letter classes.

Explore metacharacter quantifiers in grep, focusing on curly braces to specify repetition. Learn exact, at least, and range patterns with examples like the social security number format.

Learn to use regular expressions metacharacters: backslash d for digits and backslash b for word boundaries, with examples validating social security numbers and testing variable names, using grep -P.

Start with a first attempt at email validation using regex. Demonstrate a simple PHP form using preg_match, noting it remains a starting point to refine domain and top-level domain checks.

Learn to use c# to validate five-digit and plus-four zip codes with a regular expression, building and testing a pattern that matches valid zips and excludes invalid ones.

Explore regular expressions and word boundaries in Java to find cat at word starts. Learn to use backslash escapes, pattern matching, and file handling to locate matches.

Master alternation with regular expressions in JavaScript. Use the single bar to match color or colour and test for matches, optionally with word boundaries.

Explore matching text with regular expressions, focusing on detecting doubled words using back references, and learn to write a simple word pattern to find repeated words in a text file.

Learn to match text with regular expressions by escaping metacharacters, using backslashes to treat dots and question marks as literals, and applying grep-style matching.

Write a PHP regular expression to validate a date in the mm/dd/yyyy format, anchored at the start with groups for month, day, and year, used in a form.

Construct a JavaScript regex to validate times in standard format with two-digit hours, a colon, two-digit minutes, and optional space before am/pm.

Write a basic C# regular expression to match IPv4 addresses by anchoring, escaping dots, and limiting octets to three digits; apply it to a file to extract matches.

Learn to validate urls using a first regular expression that matches https, ftp, or file protocols, followed by :// and a domain, anchored at the start and the end.

Practice exercise demonstrates case-insensitive regular expression matching in C-sharp by using alternation to match lowercase and uppercase variants, reading text from a file and counting matches with a match collection.

Learn to replace text with regular expressions in Java by building a simple spelling correction tool that fixes i before e words except after c, using replaceAll on pattern matches.

Format a social security number from a digit string with PHP's preg_replace, using regular expressions to capture first three, next two, and last four digits and reassemble with dash backreferences.

Learn to replace duplicate words in a string with a regular expression in C#, using word boundaries and a back reference to keep a single copy.

Replace digits with their word representations in JavaScript by using a global regex and a two-function approach that maps digits to strings via an array.

Write a Java exercise that reads a name and grade file, uses regular expressions to locate numbers, curves them by adding five, and rebuilds updated string with a string buffer.

Explore how Java's split method uses a regular expression to divide a string into an array, demonstrated with comma-delimited text and simple no-tag HTML, and display the results.

Learn to validate passwords in javascript with an advanced regular expression using positive lookaheads, enforcing 10–20 characters, plus uppercase, lowercase, and a number on a form password field.

Validate urls with an advanced PHP regular expression that anchors the protocol and escapes slashes, matching http, https, or ftp. Demonstrate form input validation and showing valid or invalid results.

Develop and apply an advanced regular expression to verify Windows paths, requiring a drive letter, colon, and backslashes, while excluding invalid characters and filtering invalid paths like c:\program files.

practice exercise demonstrates using a javascript regex to reorder a comma-delimited name list, from first last to last, first, via the Spidermonkey command-line shell.

Go out and write regular expressions to solve real problems, applying what you learned. Explore further guidance from introducing regular expressions, mastering regular expressions, and the regular expressions cookbook.