Redirecting C++ generated cerr and cout to the same file in Ubuntu

Question

My program generates output both directed to std::cout and std::cerr. When I run a test file normally as in

./a.out <source> &> <target>  

target captures both types of output in the order produced by ./a.out.

When trying to automate testing of output for a simple unit testing framework, I implemented the above in a bash script:

 `rm $OUT_NAME`
 `./a.out $NEW_UNIT &> $OUT_NAME`   

(with the obvious variable names). The output sent to cout is printed fine; but the one sent to cerr is printed incorrectly (some is printed; then printing stops with no error). In case you wonder, I added the 'rm' first just to be perfectly sure it's no issue with over-writing/appending to an old version.

Any ideas?

My system: Ubuntu 12.04.

Answer 1

In bash, you should do the following:

./a.out source > target 2>&1

to merge stderr into stdout. The command you gave is meant for csh.

And if you want to merge stdout into stderr, you will do

./a.out source 2> target 1>&2

Answer 2

./a.out source >> target 2>&1 would solve your problem
2>&1 means that combine(or called redirect) standard error (stderr) with standard out (stdout)
>> means to attach the output stream of your program to then end of "target". And if you use a single > instead of >>, it means to replace the output stream of your program with the "target".

P.S. Suppose your code have two different output
std::cout<<"results"<<endl and some std::cerr<<"debug information"<<endl

In bash, you can do ./a.out source 1>>Result.txt 2>> Debug.txt
And your "results" would be store in Result.txt and your "debug information" would be store in Debug.txt.
1>> means standard output redirect to the back of somewhere, you can also use 1> which means standard out redirect to somewhere
2>> means standard error redirect to the back of somewhere, you can also use 2> which means standard error redirect to somewhere

That would be very useful if you want to use script automatically run your program.

Answer 3

In bash, this should work:

./a.out source >target 2>&1