via

Sometimes you want to pipe things into a process’s stdin (to emulate typing things, for example.)

echo "blah" | binary
python -c "print hello" | binary # is another common thing.

But what if you want to do that with a process you’re starting via gdb? Gets a little more complicated, but gdb has things built in to do such things.

# run it in a subshell and get the stdout fd
gdb binary
r < <(python -c "print '\x41'*36")

# bash command substitution into how gdb does stdin
r <<< $(python -c "print '\x41'*36")
# note! this handles nulls weirdly on stdin within gdb. (leakless, fireshellctf)
# the above did not have this issue.