When the command is executed in one shot mode (-o) with stdin
being something other than a terminal,  the tcgetattr() call
would fail,  and generate an error message. e.g.:

slabtop: terminal setting retrieval: Inappropriate ioctl for device
 Active / Total Objects (% used)    : 905319 / 915886 (98.8%)

Signed-off-by: Craig Small <csmall@enc.com.au>