$a is a bad choice of variable names (as would $b), since it is a magic variable used in custom sorts, however I very much doubt if that is an issue here.

The rediection should work, and the creation of the file shows that the shell (probably cmd.exe) is creating the output file. A few things spring to mind that can create issues with cmd.exe:
Does the command-line (including $a) contain any quotes (other than the outer " used for Perl interpolation)?
Does the parameter in $a contain any imbedded whitespace?

You might like to replace the ./TVT.exe with echo to eliminate these issues. If that gets redirected correctly then you might need to look at the program. For example, is it writing to STDERR?

Update: I have done some experimenting, and cmd.exe does not seem particularly happy with the ./ prefix to the exe. I know you say it worked previously, but try removing it (it is not needed in Windows because the current directory is searched, whether it is in the %path% or not).

In reply to Re: redirecting output from a system command to a text file by cdarke
in thread redirecting output from a system command to a text file by mark4444az

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