>I would constrain this even further to "Write to stdout only if information is useful as input to another program." May not always be possible to know this in

>I would constrain this even further to "Write to stdout only if information is useful as input to another program." May not always be possible to know this in advance. Might be of interest: https://www.google.com/search?q=the+unix+programming+environment https://www.google.com/search?q=the+unix+programming+environ... http://jugad2.blogspot.in/2014/09/my-ibm-developerworks-article.html http://jugad2.blogspot.in/2014/09/my-ibm-developerworks-arti... Also, stdout and stderr can be redirected independently, and either one can be redirected to the other (cmd args 2> file, 2>&1, 1>file, 1>&2, etc.). There are even more advanced options. "man bash" has the details. Edit: Fixed a URL typo.