How to run internal cmd command from the msys shell?

1. Search your %PATH% for cmd.cmd or cmd.bat. They may interfere with your cmd

2. Run Process Monitor and run your cmd /c mklink. Examine ProcMon log for really executed commands.

win7/cygwin/bash had same problem, solution is to launch cmd twice, and convert slashes to backslashes as needed by cmd (for example): REPO_DIR=${REPO_DIR////\\} # Example, Turn c:/cvs into c:\cvs for cmd
cmd /C "cmd /C mklink /D .Repo $REPO_DIR" # launch cmd /C cmd /C cmd


Process Monitor helped track down the issue. It is that msys will convert /c to c:\ ; it needs to be escaped: cmd //c mklink. The way these conversions are done is explained here. – Mihai Rotaru Jan 1 '13 at 21:32

I could not get this to work based on Mihai's comment alone, because the path still contained forward slashes / in it, and mklink complained that /msys64 was not a valid switch.

So I wrote a batch script to get it working.

Here's how I call my batch script from MSYS:

 $ mingw_ln.bat "$destination" "$targetpath"

And, the batch script takes those two paths, and converts / to \, using the :OLD=NEW parameter expansion syntax for string replacements.¹

set LINK=%1
set TARGET=%2

REM Convert POSIX paths to Windows paths
set LINK=%LINK:/=\%
set TARGET=%TARGET:/=\%

mklink /D %LINK% %TARGET%

¹ This is similar to bash's ${PARAM:/OLD/NEW} syntax, for those familiar with it

Expanding on Mihai Rotaru's comment:

Process Monitor helped track down the issue. It is that msys will convert /c to c:\ ; it needs to be escaped: cmd //c mklink. The way these conversions are done is explained here. – Mihai Rotaru Jan 1 '13 at 21:32

This /c to c:\ conversion can also be avoided for some or all arguments by using the environment variable MSYS2_ARG_CONV_EXCL.

E.g.

$ MSYS2_ARG_CONV_EXCL='*' /c/Windows/System32/cmd.exe /C "echo foo"

(Careful since '*' and "*" will mean different things.)

Citing the MSYS2 docs:

MSYS2_ARG_CONV_EXCL can either be * to mean exclude everything, or a list of one or more arguments prefixes separated by ;, like MSYS2_ARG_CONV_EXCL=--dir=;--bla=;/test [...]