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 '...'?
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
python generate_lots_of_data.py | ./process-to-debug it's already got input going to it. If you only want to send input to the process when you're ready for it, use the fifo approach.cat in one terminal and attach gdb to it in another. Since cat is just sitting there waiting for input, you can manually send it something and watch it get processed. For programmatic output, though, you'll want a FIFO.