The commands below are for the Fish shell, but most of them work with Bash too.
$ ./a.out > out.txt
$ ./a.out < in.txt
$ ./a.out ^ out.txt
$ ./a.out > out.txt 2>&1
Note how the binding of stderr (2) to stdout (1) is placed after the filename.
$ ./a.out | less
$ ./a.out ^| less
$ ./a.out 2>&1 | less
Reference: Redirections section of the Bash manual.
Tried with: Fish 2.7.1 and Ubuntu 16.04