long paths on windows?

\\?\

MAX_PATH limitations

• 260 characters
• -3: drive letter, colon, backslash: "C:\"
• -1: terminating NUL character
• -12: directory must allow for an "8.3 filename"
• ~244 characters for a directory structure

8.3 filename

• aka short filename
• up to 8 characters for filename
• up to 3 characters for extension
• shortened by use of ~ + ordinal:
  • LONGFI~1.TXT for longfilename.txt

enabling long paths

• via registry
  • HKLM\SYSTEM\CurrentControlSet\Control\FileSystem LongPathsEnabled=1
• group policy
  • Computer Configuration > Administrative Templates > System > Filesystem > Enable NTFS long paths
• may not apply to 32 bit programs

extended length paths

• prefix with \\?\
• up to ~32,767 characters (may be subject to path expansion)
• do not go undergo usual path normalizations
  • cannot use forward slashes as separators
• "\\?\C:\very\long\path\..."

real world problem

• pre-commit is a multi-language git hooks framework
• multi-language multi-platform hooks
  • including nodejs
• must be able to install deeply nested node_modules
• current npm requires 199 characters (!)