Ignore empty results for xargs in Mac OS X

Question

The code for my website uses this piece of code for automatic deployment on the server (Ubuntu).

cmd = \'cd \' + checkout_dir + \' && \' +

Answer 1

Not pretty, but hopefully a workaround.

cmd = 'cd ' + checkout_dir + ' && ' + 
    'r=$(' svn_command + ' st | ' +
        "awk '$2 !~ /^deploy/{print $2}' | tac) && " +
    'test "$r" && ' +
    svn_command + ' revert -R $r && ' +
    svn_command + ' up -r ' + options.revision

I'm not convinced that the tac is necessary or useful. I refactored the first grep into the Awk script for efficiency and aesthetic reasons.

To solve the general "my xargs lacks -r" problem, the gist of the solution is to convert

stuff | xargs -r cmd

into

var=$(stuff)
test "$var" && cmd $var

The unquoted $var will only work if it doesn't contain file names with spaces or other surprises; but then bare-bones xargs without the GNU extensions suffers from the same problem.