If you can't recompile the program, an expect script will come very handy: $ ./unbuffer ./tst >/tmp/logit 2>&1; cat /tmp/logit line 1 stderr line 1 lin

If you can't recompile the program, an expect script will come very handy: $ ./unbuffer ./tst >/tmp/logit 2>&1; cat /tmp/logit line 1 stderr line 1 line 2 stderr line 2 http://expect.nist.gov/example/unbuffer http://expect.nist.gov/example/unbuffer