np — Path Normalizer for Windows

np converts path spellings from coding agents or other operating systems to Windows form for use in cmd.exe or PowerShell. It converts separators, expands a leading ~, and translates drive spellings such as /mnt/c/users/me to C:\users\me. It detects whether you ran it from cmd.exe or PowerShell and spells and quotes the result for that shell.

For example, with USERPROFILE=C:\Users\me:

> np ~/mystuff/projects/cli_utils/normpath.git
C:\Users\me\mystuff\projects\cli_utils\normpath.git

PS> np ~/mystuff/projects/cli_utils/normpath.git
C:/Users/me/mystuff/projects/cli_utils/normpath.git

np converts input text to Windows path text, reading USERPROFILE only to expand a leading ~. It checks some lexical rules but never consults the filesystem or the current directory. The output is not verified: it may still be invalid or refer to a location that does not exist.

Getting Started

np.exe runs on Windows 10 version 1903 or later, x64. The examples below use cmd.exe unless the prompt is PS>; Shell-Aware Output describes the PowerShell differences.

np, np -h, and np --help show the same usage and options. np --version shows version information. The seven-character Git revision has a -dev suffix when the checkout contains uncommitted changes or untracked files at build time. Git-ignored files do not count.

Building and Testing

The project uses C++23 and Windows x64 toolchains. Follow Building and testing np to build the executable and run the tests and development checks. Then copy np.exe to a directory on your PATH. The executable is standalone; no installer is needed.

Converting Paths

Pass one or more paths as arguments. np prints each converted path on its own line:

> np C:/work/project/src
C:\work\project\src

> np src/main.cpp
src\main.cpp

Both / and \ are accepted as separators. np also recognizes Unix-style drive spellings and removes redundant separators and . or .. segments. Relative paths stay relative; np never prepends the current directory.

A single period attached to the final filename is treated as sentence punctuation and removed: d:\dir1\dir2\dir3. becomes D:\dir1\dir2\dir3. This applies to arguments and stdin. . and .. path segments keep their normal meaning; periods inside names and UNC server/share fields are preserved.

Input	Output
/c/work, /mnt/c/work	C:\work
src/../include	include
../src	..\src
//server/share/dir	\\server\share\dir
smb://server/share/dir	\\server\share\dir

smb://server/share[/path] also accepts a case-insensitive smb: prefix. Server and share are required. Use literal spaces; percent signs and URL encoding are rejected. Credentials, ports, IPv6 literals, backslashes, queries, and fragments are unsupported in SMB inputs.

In cmd.exe, when the converted path contains a space or any of & ( ) ^, np wraps the path in double quotes. The input needs quotes for the same reason; cmd.exe consumes those before np sees the path. % and ! do not trigger quotes, and quoting does not suppress cmd.exe variable expansion.

> np "C:/my projects/app"
"C:\my projects\app"

If a path is rejected, np reports an error on stderr and continues with any remaining paths.

Shell-Aware Output

In PowerShell 7 and Windows PowerShell 5.1, np prints forward slashes. It adds single quotes where needed to preserve the path text and doubles embedded single quotes:

PS> np "C:\my projects\app"
'C:/my projects/app'

PS> np "C:\Users\Paul's files"
'C:/Users/Paul''s files'

Detection uses the immediate parent process; other or unavailable parents default to cmd.exe output. Thus, cmd /c np uses cmd.exe output even when invoked from PowerShell.

PowerShell cmdlets that take -Path treat [ and ] as wildcards; quoting does not change that. For such names, pass the path with -LiteralPath.

Reading Paths from stdin

Use - to read one path per line from a UTF-8 text file. Do not quote paths in the file.

For example, paths.txt:

C:/my projects/app
src/main.cpp

> np - < paths.txt
"C:\my projects\app"
src\main.cpp

You can also pipe paths into np:

type paths.txt | np -

PowerShell has no < redirection; pipe the file instead:

Get-Content -Encoding UTF8 paths.txt | np -

In Windows PowerShell 5.1, first set $OutputEncoding = [Text.UTF8Encoding]::new($false) to preserve non-ASCII characters in piped input. PowerShell 7 already uses UTF-8.

To enter paths interactively, run np -. Press Ctrl+Z, then Enter, to end input.

Rejected Inputs

np rejects these path forms:

• Drive-relative input such as C:foo or C:
• The \\?\ and \\.\ namespace prefixes
• UNC paths without both a server and a share
• Normalization that changes the root, such as ./c:/foo or \\server\share\..\other

Filename components surviving normalization are rejected for:

• Prohibited characters: < > : " | ? * or control characters (U+0000–U+001F)
• Reserved device names, with or without an extension: CON, PRN, AUX, NUL, COM1–COM9, or LPT1–LPT9 (case-insensitive, including the superscript digits ¹, ², and ³ for COM and LPT)
• A trailing space or period remaining after the sentence-period removal

The drive designator and UNC server and share are root fields, not filename components; UNC server and share fields are checked for control characters. Length is never checked, and rejection is lexical, not a filesystem or security check.

Exit Status

Status	Meaning
0	All inputs converted, help/version delivered, or empty stdin
1	Processing completed with at least one input rejected
2	Invocation aborted; takes precedence over 1

Aborts include usage errors (such as np -- without paths), stream failures, and unexpected failures.