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Regex - File Path - Windows

^(?:[\w]\:|\\)(\\(?!\.+)[A-Za-z_\-\s0-9\.\$]+)+$

Works….

(?:[\w]\:

(?:[\w]\:

([a-z_\-\s\0-9\.\\]+)+([a-z_\-\s\0-9\.]+)(\\)([a-z_\-\s\0-9]+)$

^(?:[\w]\:|\\)(\\[a-z_\-\s0-9\.]+)+\.(txt|gif|pdf|doc|docx|xls|xlsx)$

^(?:[\w]\:|\\)(\\[a-z_\-\s\0-9\.]+)+(?:\\)([a-z_\-\s\0-9]+){1}$

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


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

Windows

(\\\\([a-z|A-Z|0-9|-|_|\s]{2,15}){1}(\.[a-z|A-Z|0-9|-|_|\s]{1,64}){0,3}){1}(\\[^\\|\/|\:|\*|\?|"|\<|\>|\|]{1,64}){1,}(\\){0,}

NOTE: Disallows a few characters: \/:*?"<>|.

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

^[a-zA-Z]:\\(((?![<>:"/\\|?*]).)+((?<![ .])\\)?)*$

NOTE: It makes the path conform to the NTFS standard (see the MSDN spec).

^[a-zA-Z]:\\ matches single drive letter, with colon and backslash

(?![<>:"/\\|?*]) is a negative lookahead to ensure the next character is not invalid

((?![<>:"/\\|?*]).)+ wraps that lookahead, followed by the next character, any number of times

(?<![ .])\\ is a negative lookbehind to ensure the file/directory doesn't end with a space or period. Please note: Lookbehinds are not fully implemented everywhere just yet.

All of that is is repeated 0 to many times, with the last backslash optional.

For many use cases it may be best to restrict the path length to 256 characters.

To do so, replace *with {0,256}.