Pipe to a file

I use the NSIS commands

GetTempFileName $R1
ExecWait "kpsewhich -expand-var=$$TEXMF > $R1"

However the redirection seems to be ignored. How can I achieve the desired effect?

You have to use command.com/cmd.exe to interpet this. Use ReadEnvStr %COMPSPEC% to get the path of command.com/cmd.exe and then execute it with /C your command.

ReadEnvStr $0 COMSPEC
ExecWait "$0 /c myProg.exe > bla.txt"