Date: 2009sep4 OS: Linux Language: C/C++ Q. C/C++: How can my program tell if it's output has been redirected? A. This does the trick:

#include <io.h> const bool bInteractive = isatty(fileno(stdout));

Example use:

if (isatty(fileno(stdout))) { printf("We ARE interactive (no redirection)\n"); } else { printf("We are NOT interactive (being redirected)\n"); }

This works on Linux and Borland C++ 5.x (which is nice). The Linux "less" command uses this. If you do:

less myfile.txt

Then less pages the file. And you can scroll backwards and forwards. But if you do:

less myfile.txt > anotherfile.txt

Then less does not offer any paging.