Teeing up your output

I was on customer site this week running some good old cmd scripts on a Windows Server that output to standard output, or stdout as we say in the Linux/Unix world, so showed in the cmd prompt that I’d run them from. But what I also needed as well as seeing the results as they happened was to record the output to a file in case I needed to refer back to any specific piece of it later given that it was running against nearly 6000 users.

Enter the Unix/Linux “tee” command that outputs to standard output as well as to a file. This is available through packages such as Cygwin but when on customer site you typically need access to a standalone executable that doesn’t need installing that you can just copy to the required system and run. To that end, here is my implementation of the “tee” utility that I wrote many years ago that will serve the purpose required.

At its simplest, it just takes an output file name that is overwritten with whatever it is piped to it so is invoked thus:

yourscript.cmd your parameters | tee outputfile.log

If you also want to catch errors then you need to do the following which is “stolen” directly from Unix shell scripting:

yourscript.cmd your parameters 2>&1 | tee outputfile.log

Since “2” is the file number for standard error (stderr) and “1” is the file number for standard output (stdout).

By default it overwrites the output file but specify a -a argument and it will append to an existing file and use -b if you have long line lengths as it reads a line at a time. Run with -? to see a usage message.

You can download the tool here but as ever it comes with absolutely no warranty and you use it entirely at your own risk (not that there’s any risk but I have to say that, don’t I?).

Yes, I know that tee, or tee-object, exists in PowerShell 3.0 and higher but sadly we still can’t guarantee that we have this on customer systems, much as I like PowerShell.


Author: guyrleech

I wrote my first (Basic) program in 1980, was a Unix developer after graduation from Manchester University and then became a consultant, initially with Citrix WinFrame, in 1995 and later into Terminal Server/Services and more recently virtualisation, being awarded the VMware vExpert status in 2009 and 2010. I have also had various stints in Technical Pre-Sales, Support and R&D. I work as a Senior Technical Consultant for HCL, live in West Yorkshire, England; have a wife, three children and three dogs and am a keen competitive runner when not injured.

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