How to redirect STDOUT of a program to STDIN of a GDB-debugged program?

Question

I normally redirect STDOUT to another program using:

python -c 'print("HelloWorld")' | ./myprog

I know that I can supply the contents of a file as STDIN for a debugged program in GDB:

(gdb) run myprog < input.txt

However, how can I do something like:

(gdb) run mypprog < python -c 'print("HelloWorld")'

without first having to create a file with the output of python -c '...' ?

Answer 1

One way is to attach gdb to your already-running process. Find its pid with ps or top . Let's say that it's 37. Then run

(gdb) attach 37

That probably won't work for your case with very short run time though. Another approach is to use a fifo .

mkfifo fifo
python -c 'print("Hello World")' > fifo &
gdb myprog
run < fifo