tony@scirtp.UUCP (t e bennett) (02/19/88)
A question regarding sxt's, pty's and ISIG on 5.3 386. We noticed recently that if a user is logged into a shell layer on a tty line and then rlogin's into a shell on another machine, that ^Z will not cause the switch back to shl's '>>>' prompt. A little investigation showed the reason was that rlogin/telnet had turned off ISIG which disabled the check for the switch character (as well as for INTR and QUIT). Our first attempt to work around this problem (we consider it a problem, anyway) involved having rlogin not turn off ISIG, but to change its VINTR and VQUIT to 0377. This worked, but has the effect of precluding any type of umodem/kermit file xfer thru the rlogin/telnet (something we actually do), since 0377 would now hit the rlogin with a SIGQUIT. Our next thought was this: Is it really in the spirit of things for ISIG to control VSWTCH? It looks like ISIG was designed to give the process the ability to not be subject to interrupts. Should VSWTCH be considered in the same class? (Note that the 5.3 documentation quite clearly does say that ISIG controls VSWTCH) The effect of this is that any application program that wants to ignore signals will also disable shell layer switching. Any thoughts on this? Please respond by mail. (sxt driver unchanged from 5.3 pty driver from Micom-Interlan with minor changes) --tony t e bennett {decvax,akgua}!mcnc!rti!scirtp!tony