linux - 线下机器ssh服务器， stty -a 后，查看到的结果是 0 或是 undef ，有谁知道是什么情况，我本地怎么设置吗

Question

为什么很多配置都的undef 和 0 呢？

speed 0 baud; rows 0; columns 0; line = 0;
intr = ; quit = ; erase = ; kill = ; eof = ;
eol = ; eol2 = ; swtch = ; start = ; stop = ;
susp = ; rprnt = ; werase = ; lnext = ;
flush = ; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts -cdtrdsr
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr -icrnl -ixon -ixoff
-iuclc -ixany -imaxbel -iutf8
-opost -olcuc -ocrnl -onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
-isig -icanon -iexten -echo -echoe -echok -echonl -noflsh -xcase -tostop -echoprt
-echoctl -echoke

Answer 1

man stty, it is written very clearly.

PS. The OSX man page says it more clearly:
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/stty.1.html