How to log make output without buffering from stdout and stderr

Question

I am having a problem with logging to output from an automated build.

The build is done with a Makefile and the makefile utility.

The problem is that normal output like compiler command lines go to stdout and compile errors go to stderr.

I want to get the output from the build as it would show on the screen. So something like:

(stdout) CC -c file.cpp
(stderr) Compile error at file.cpp line 232, blah blah blah
(stdout) CC -c file2.cpp

What I tried (from a ksh script) is:

make -k > build.log 2> build.log

This results in a single log file but the problem is that the streams are buffered and so the result in the log file is all mixed up.

I could capture the output into 2 separate log files but then I would have no info on how to glue them back together into a single log file.

Is there a way to turn off buffering for stdout and stderr in this case?

Answer 1

Try this

make -k > build.log 2>&1

Answer 2

make -k > build.log 2>&1

This should work better for you because it is not redirecting stderr and stdout separately, but redirecting stderr to stdout, which should make the buffering sync up.

Answer 3

I could capture the output into 2 separate log files but then I would have no info on how to glue them back together into a single log file.

Gluing them back together is tricky but there is a right answer for that too, and it works! See "How do I save or redirect stdout and stderr into different files?" by Vivek Gite.

Answer 4

setbuf(stdout,NULL); ->turns off stdout buffering