Exploring Expect

Bugs And Workarounds

On some systems, bugs in the operating system prevent correct operation of "spawn -open [open . . .]" on some special files. For example, on SunOS, Expect cannot detect an eof from a fifo. Yet another operating system bug prevents AIX 3.2 from detecting input from physical tty devices.^[46]

Fortunately, OS bugs like these are infrequent but Expect does a number of unusual things and you must gird yourself to work around such bugs. In the next section, I will describe a workaround for the fifo problem. A similar workaround can be applied to the other problem.

^[46] The effect of this particular bug also shows up in the failure of expect_user to read input. A patch is available from the vendor.