On Linux, is there a way for a shell script to check if its standard input is redirected from the null device (1, 3) *, ideally without reading anything?
The expected behavior would be:
./checkstdinnull -> no ./checkstdinnull < /dev/null -> yes echo -n | ./checkstdinnull -> no EDIT mknod secretunknownname c 1 3 exec 6<secretunknownname rm secretunknownname ./checkstdinnull <&6 -> yes
I suspect I "just" need to read the maj/min number of the input device. But I can't find a way of doing that from the shell.
*No necessary just
/dev/null, but any null device even if manually created with