Is there a simple utility which I can pipe output to on Linux that will:Return a success code if there is no output on standard out (and / or standard error).Return a failure code if output is produced on standard out (and / or standard error).To provide some context, the command I'm running is:svn mergeinfo --show-revs eligiblehttp://mysvnserver.example.com/SVF/repos/common/abc/branches/abc-1.7http://mysvnserver.example.com/SVF/repos/common/abc/trunkIf there are any unmerged entries on the branch, the command will return a list of revision numbers on standard out. Ideally, the additional command that I'm talking about would:Detect entries on standard out and return an error condition to Linux.Pass on the standard out so that it does end up appearing on the terminal. I'd rather not suppress it.
Linux command line that will fail if any standard out is produced
shell script;text processing
That's grep you're looking for:if svn ... 2>&1 | grep '^'; then  echo there was some outputelse  echo there wasn'tfiYou can replace grep '^' with grep . or grep '[^[:blank:]]' to check for non-empty or non-blank lines (but that will remove the empty/blank ones from the output).(note the behaviour will vary across grep implementations if the input contains non-text data like NUL bytes or too long or non-terminated lines (which wouldn't happen for svn though)).