Windows PATH to posix path conversion in bash

I don't know msys, but a quick google search showed me that it includes the sed utility. So, assuming it works similar in msys than it does on native Linux, here's one way how to do it:

From Windows to POSIX

You'll have to replace all backslashes with slashes, remove the first colon after the drive letter, and add a slash at the beginning:

echo "/$pth" | sed 's/\\/\//g' | sed 's/://'

or, as noted by xaizek,

echo "/$pth" | sed -e 's/\\/\//g' -e 's/://'

From POSIX to Windows

You'll have to add a semi-colon, remove the first slash and replace all slashes with backslashes:

echo "$pth" | sed 's/^\///' | sed 's/\//\\/g' | sed 's/^./\0:/'

or more efficiently,

echo "$pth" | sed -e 's/^\///' -e 's/\//\\/g' -e 's/^./\0:/'

where $pth is a variable storing the Windows or POSIX path, respectively.

Cygwin, Git Bash, and MSYS2 have a readymade utility called cygpath.exe just for doing that.

Output type options:  -d, --dos             print DOS (short) form of NAMEs (C:\PROGRA~1\)  -m, --mixed           like --windows, but with regular slashes (C:/WINNT)  -M, --mode            report on mode of file (binmode or textmode)  -u, --unix            (default) print Unix form of NAMEs (/cygdrive/c/winnt)  -w, --windows         print Windows form of NAMEs (C:\WINNT)  -t, --type TYPE       print TYPE form: 'dos', 'mixed', 'unix', or 'windows'

Just use cygpath:

$ cygpath -w "/c/foo/bar" -> C:\foo\bar$ cygpath -u "C:\foo\bar" -> /c/foo/bar

You may wonder: "Do I have cygpath installed?" Well,

1. If you're using the git-bash shell, then yes.
2. If you're in cygwin, then yes.
3. If you're in another shell, but you have installed git-bash before, then cygpath can be found at git-bash-install-folder\usr\bin\cygpath.exe.
4. Else: maybe not, but I'm sure you can find a way to installed it.