Can the shell warn me if a program is waiting for standard input?

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http://unix.stackexchange.com – Let's say I want to search for a string in a big file: grep foo bar.txt | less, but I actually type grep foobar.txt | less. Now, grep is waiting for me to type something on the terminal. It appears that the command is taking forever, until I notice my mistake. Can the shell (any shell, or perhaps tmux) detect that a command is waiting for console input, and warn me? (HowTos)