Regular Expressions Cookbook

7.18. Validate Windows Paths

Problem

You 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
[a-z]:\\                    # Drive
(?:[^\\/:*?"<>|\r\n]+\\)*   # Folder
[^\\/:*?"<>|\r\n]*          # File
\Z

Regex options: Free-spacing, case insensitive

Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby

^[a-z]:\\(?:[^\\/:*?"<>|\r\n]+\\)*[^\\/:*?"<>|\r\n]*$

Regex options: Case insensitive

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python

Drive letter and UNC paths

\A
(?:[a-z]:|\\\\[a-z0-9_.$]+\\[a-z0-9_.$]+)\\  # Drive
(?:[^\\/:*?"<>|\r\n]+\\)*                    # Folder
[^\\/:*?"<>|\r\n]*                           # File
\Z

Regex options: Free-spacing, case insensitive

Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby

^(?:[a-z]:|\\\\[a-z0-9_.$]+\\[a-z0-9_.$]+)\\(?:[^\\/:*?"<>|\r\n]+\\)*↵
[^\\/:*?"<>|\r\n]*$

Regex options: Case insensitive

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python

Drive letter, UNC, and relative paths

\A
(?:(?:[a-z]:|\\\\[a-z0-9_.$]+\\[a-z0-9_.$]+)\\|    # Drive
   \\?[^\\/:*?"<>|\r\n]+\\?)                       # Relative path
(?:[^\\/:*?"<>|\r\n]+\\)*                          # Folder
[^\\/:*?"<>|\r\n]*                                 # File
\Z

Regex options: Free-spacing, case insensitive

Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby

^(?:(?:[a-z]:|\\\\[a-z0-9_.$]+\\[a-z0-9_.$]+)\\|\\?[^\\/:*?"<>|\r\n]+\\?)↵
(?:[^\\/:*?"<>|\r\n]+\\)*[^\\/:*?"<>|\r\n]*$

Regex options: Case insensitive

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python

Discussion

Drive letter paths

Matching a full path to a file or folder on a drive ...