URLs, Paths, and Internet Addresses Back
What this chapter mainly concerns a wide range of programs is the various paths and locators for finding data:
- URLs, URNs, and related strings
- Domain names
- IP addresses
- Microsoft Windows file and folder names
Validating URLs
Problem
How to check whether a give piece of text is a URL that is valid?
Solution
Allow almost any URL:
/^(https?|ftp|file):\/\/.+$/i
Require a domain name, and don't alow a username or password:
/^(https?|ftp):\/\/[a-z0-9-]+(\.[a-z0-9-]+)+([\/?].+)?$/i
Require a domain name, and don't allow a username or password. Allow the scheme (http or ftp) to be omitted if it can be inferred from the subdomain (www or ftp):
/^((https?|ftp):\/\/|(www|ftp)\.)[a-z0-9-]+(\.[a-z0-9-]+)+([\/?].*)?/i
Require a domain name and a path that points to an image file. Don’t allow a username, password, or parameters:
/^(https?|ftp):\/\/[a-z0-9-]+(\.[a-z0-9-]+)+(\/[\w-]+)*\/[\w-]+\.(gif|png|jpg)$/i
Finding URLs within full text
Problem
You may want to find URLs in a large body of text.
Solution
URL without spaces:
/\b(https?|ftp|file):\/\/\S+/i
URL without spaces or final punctuation:
/\b(https?|ftp|file):\/\/[-A-Z0-9+&@#/%?=~|$!:,.;]*[A-Z0-9+&@#/%=~|$]/i
URL without spaces or final punctuation. URLs that start with the www or ftp subdomain can omit the scheme:
/\b((https?|ftp|file):\/\/|(www|ftp)\.)[-A-Z0-9+&@#/%?=~|$!:,.;]*[A-Z0-9+&@#/%=~|$]/
Validating URNs
Problem
You may want to check whether a string represents a valid Uniform Resource Name, or find URNs in a large body of text?
Solution
Check whether a string consists entirely of a valid URN:
/^urn:[a-z0-9][a-z0-9-]{0,31}:[a-z0-9()+,\-.:=@;$_!*'%\/?#]+$/
Find a URN in a large body of text:
/\burn:[a-z0-9][a-z0-9-]{0,31}:[a-z0-9()+,\-.:=@;$_!*'%\/?#]+/
Validating generic URLs
Problem
You may want to check whether a given piece of text is a valid URL according to RFC 3986.
Solution
/^([a-z][a-z0-9+\-.]*:(\/\/([a-z0-9\-.~%!$&'()*+,;=]+@)?([a-z0-9\-.~%]+|\[[a-f0-9:.]+\]|\[v[a-f0-9][a-z0-9\-.~%!$&'()*+,;=:]+\])(:[0-9]+)?(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?|(\/?[a-z0-9\-.~%!$&'()*+,;=:@]+(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?)?)|([a-z0-9\-.~%!$&'()*+,;=@]+(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?|(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)+\/?)) (\?[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?(#[a-z0-9\-._~%!$&'()*+,;=:@\/?]*)?$/
Extract the Scheme from a URL
Problem
How to extract the URL scheme from a string that holds a URL. For example, extract http from http://www.regexcookbook.com.
Solution
**Extract the scheme from a URL known to be valid
/^([a-z][a-z0-9+\-.]*):/i
Extract the scheme while validating the URL
/^([a-z][a-z0-9+\-.]*):(\/\/([a-z0-9\-.~%!$&'()*+,;=]+@)?([a-z0-9\-.~%]+|\[[a-f0-9:.]+\]|\[v[a-f0-9][a-z0-9\-.~%!$&'()*+,;=:]+\])(:[0-9]+)?(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?|(\/?[a-z0-9\-.~%!$&'()*+,;=:@]+(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?)?)(\?[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?(#[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?$/i
Extract the host from a URL
Problem
How to extract the host from a string that holds a URL. For example, extract www.regexcookbook.com from http://www.regexcookbook.com.
Solution
Extract the host from a URL known to be valid:
/^[a-z][a-z0-9+\-.]*:\/\/([a-z0-9\-.~%!$&'()*+,;=]+@)?([a-z0-9\-.~%]+|\[[a-z0-9\-._~%!$&'()*+,;=:]+\])/i
Extract the host while validating the URL:
/^[a-z][a-z0-9+\-.]*:\/\/([a-z0-9\-.~%!$&'()*+,;=]+@)?([a-z0-9\-.~%]+|\[[a-f0-9:.]+\]|\[v[a-f0-9][a-z0-9\-.~%!$&'()*+,;=:]+\])(:[0-9]+)?(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?(\?[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?(#[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?$/i
Extracting the port from a URL
Problem
You want to extract the port number from a string that holds a URL. For example, extract 80 from http://www.regexcookbook.com:80/.
Solution
Extract the port from a URL known to be valid:
/^[a-z][a-z0-9+\-.]*:\/\/([a-z0-9\-.~%!$&'()*+,;=]+@)?([a-z0-9\-.~%]+|\[[a-z0-9\-._~%!$&'()*+,;=:]+\]):([0-9]+)/i
Extract the port while validating the URL:
/^[a-z][a-z0-9+\-.]*:\/\/([a-z0-9\-.~%!$&'()*+,;=]+@)?([a-z0-9\-.~%]+|\[[a-f0-9:.]+\]|\[v[a-f0-9][a-z0-9\-.~%!$&'()*+,;=:]+\]):([0-9]+)(\/[a-z0-9\-.~%!$&'()*+,;=:@]+)*\/?(\?[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?(#[a-z0-9\-.~%!$&'()*+,;=:@\/?]*)?$/i
Extracting the path from a URL
Problem
You want to extract the path from a string that holds a URL. For example, extract /index.html from http://www.regexcookbook.com/index.html or from /index.html#fragment.
Solution
Extract the path from a string known to hold a valid URL, even if URLs that have no path:
/^([a-z][a-z0-9+\-.]*:(\/\/\\/?#+)?)?([a-z0-9\-._~%!$&'()*+,;=:@\/]*)/i
Extracting the query from a URL
Problem
You may want to extract he query from a string that holds a URL. For example, extract param=value from http://www.regexcookbook.com?param=value or from /index.html?param=value.
Solution
Extracting the fragment from a URL
Problem
You want to extract the fragment from a string that holds a URL. For example, extract top from http://www.regexcookbook.com#top or from /index.html#top.
Solution
/#(.+)/i
Validating domain names
Problem
You want to check whether a string looks like it may be a valid, fully qualified domain name, or find such domain names in longest text.
Solution
Check whether a string looks like a valid domain name:
/^([a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}$/i
Find valid domain names in longest text:
/\b([a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}\b/i
Check whether each part of the domain is not longer than 63 characters:
/\b((?=[a-z0-9-]{1,63}\.)[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b/i
Allow internationalized domain names using the punycode (域名系統) notation:
/\b((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}\b/i
Check whether each part of the domain is not longer than 63 characters, and allow internationalized domain names using the punycode notation:
/\b((?=[a-z0-9-]{1,63}\.)(xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,63}\b/i
Matching IPv4 addresses
Problem
How to use regular expressions to match IPv4 addresses like 0.0.0.0?
Solution
Simple regex to check for an IP address:
/^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$/
Accurate regex to check for an IP address, allowing leading zeros:
/^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/
Accurate regex to check for an IP address, disallowing leading zeros:
/^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9]).){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])$/
Simple regex to extract IP addresses from longer text:
/\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b/
Accurate regex to extract IP addresses from longer text, allowing leading zeros:
/\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/
Accurate regex to extract IP addresses from longer text, disallowing leading zeros:
/\b(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\b/
Simple regex that captures the four parts of the IP address:
/^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$/
Accurate regex that captures the four parts of the IP address, allowing leading zeros:
/^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/
Accurate regex that captures the four parts of the IP address, disallowing leading zeros:
/^(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])$/
Matching IPv6 addresses
Problem
How to use regular expressions to match IPv6 addresses like 0:0:0:0:0:0:0:0?
Solution
Check whether the whole subject text is an IPv6 address using standard notation:
/^(?:[A-F0-9]{1,4}:){7}[A-F0-9]{1,4}$/i
Check whether the whole subject text is an IPv6 address using mixed notation:
/^(?:[A-F0-9]{1,4}:){6}(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])$/i
Check whether the whole subject text is an IPv6 address using standard or compressed notation:
/^(?:(?:[A-F0-9]{1,4}:){7}[A-F0-9]{1,4}|(?=(?:[A-F0-9]{0,4}:){0,7}[A-F0-9]{0,4}$)(([0-9A-F]{1,4}:){1,7}|:)((:[0-9A-F]{1,4}){1,7}|:)|(?:[A-F0-9]{1,4}:){7}:|:(:[A-F0-9]{1,4}){7})$/i
Check whether the whole subject text is an IPv6 address using compressed or noncompressed mixed notation:
/^(?:(?:[A-F0-9]{1,4}:){6}|(?=(?:[A-F0-9]{0,4}:){0,6}(?:[0-9]{1,3}\.){3}[0-9]{1,3}$)(([0-9A-F]{1,4}:){0,5}|:)((:[0-9A-F]{1,4}){1,5}:|:)|::(?:[A-F0-9]{1,4}:){5})(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/i
Check whether the whole subject text is an IPv6 address:
/^(?:(?:(?:[A-F0-9]{1,4}:){6}|(?=(?:[A-F0-9]{0,4}:){0,6}(?:[0-9]{1,3}\.){3}[0-9]{1,3}$)(([0-9A-F]{1,4}:){0,5}|:)((:[0-9A-F]{1,4}){1,5}:|:)|::(?:[A-F0-9]{1,4}:){5})(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])|(?:[A-F0-9]{1,4}:){7}[A-F0-9]{1,4}|(?=(?:[A-F0-9]{0,4}:){0,7}[A-F0-9]{0,4}$)(([0-9A-F]{1,4}:){1,7}|:)((:[0-9A-F]{1,4}){1,7}|:)|(?:[A-F0-9]{1,4}:){7}:|:(:[A-F0-9]{1,4}){7})$/i
Validate windows paths
Problem
You may want to check whether a string looks like a valid path to a folder or file on the Microsoft Windows operating system.
Solution
Drive letter paths:
/^[a-z]:\\(?:[^\\/:*?"<>|\r\n]+\\)*[^\\/:*?"<>|\r\n]*$/i
Drive letter and UNC paths
/^(?:[a-z]:|\\\\[a-z0-9.$ -]+\\[a-z0-9.$ -]+)\\(?:|\\r\\n" id="reffn_\\\\/:*?"<>|\\r\\n">\\\\/:*?"<>|\\r\\n+\)*|\\r\\n" id="reffn_\\\\/:*?"<>|\\r\\n">\\\\/:*?"<>|\\r\\n*$/i
Drive letter, UNC, and relative paths
/^(?:(?:[a-z]:|\\\\[a-z0-9.$ -]+\\[a-z0-9.$ -]+)\\|\\?[^\\/:*?"<>|\r\n]+\\?)(?:[^\\/:*?"<>|\r\n]+\\)*[^\\/:*?"<>|\r\n]*$/i
Split windows paths into their parts
Problem
If a string turns out to hold a valid Windows path, then you may want to extract the drive, folder, and filename parts of the path separately.
Solution
Drive letter paths:
/^([a-z]:)\\((?:[^\\/:*?"<>|\r\n]+\\)*)([^\\/:*?"<>|\r\n]*)$/i
Drive letter and UNC paths
/^([a-z]:|\\\\[a-z0-9.$ -]+\\[a-z0-9.$ -]+)\\((?:[^\\/:*?"<>|\r\n]+\\)*)([^\\/:*?"<>|\r\n]*)$/i
Drive letter, UNC, and relative paths
/^([a-z]:\\|\\\\[a-z0-9.$ -]+\\[a-z0-9.$ -]+\\|\\?)((?:[^\\/:*?"<>|\r\n]+\\)*)([^\\/:*?"<>|\r\n]*)$/i
Extract the driver letter from a windows path
Problem
How to extract the drive letter from a windows path? For example, extract c from c:\folder\file.ext.
Solution
/^([a-z]):/i
Extract the server and share from a UNC path
Problem
How to extract the server and share from a UNC path? For example, extract server and share from \\server\share\folder\file.ext.
Solution
/^\\\\([a-z0-9.$ -]+)\\([a-z0-9.$ -]+)/i
Extract the folder from a windows path
Problem
How to extract the folder from a windows path? For example, extract \folder\subfolder\ from c:\folder\subfolder\file.ext or \\server\share\folder\subfolder\file.ext.
Solution
/^([a-z]:|\\\\[a-z0-9.$ -]+\\[a-z0-9.$ -]+)?((?:\\|^)(?:[^\\/:*?"<>|\r\n]+\\)+)/i
Extract the filename from a windows path
Problem
How to extract the filename from a windows path? For example, extract file.ext from c:\folder\file.ext.
Solution
/[^\\/:*?"<>|\r\n]+$/i
Extract the file extension from a windows path
Problem
How to extract the file extension from a windows path? For example, extract .ext from c:\folder\file.ext.
Solution
/\.[^.\\/:*?"<>|\r\n]+$/i
Strip invalid characters from filenames
Problem
You may want to strip a string of characters that are not valid n windows filenames.
Solution
function stripInvalidCh(subject) { subject = subject.replace(/[\\\/:"*?<>|]+/, '_'); }
As the plugin is integrated with a code management system like GitLab or GitHub, you may have to auth with your account before leaving comments around this article.
Notice: This plugin has used Cookie to store your token with an expiration.