robg@mmintl.UUCP (Robert Goldman) (06/14/85)
I am working on a program that needs to access the terminal in a pretty raw state. In particular, it must have some way to tell whether there are any keys in the input buffer waiting to be read. Is there some portable unix call that responds with this information? A getchar()-type function that doesn't wait for input? I'd appreciate any help you can give me. Robert Goldman MultiMate International P.S. If you are answering from net.unix-wizards, please send answer via mail -- I'm not wizardly enough for this newsgroup. :-(
psc@lzwi.UUCP (Paul S. R. Chisholm) (06/18/85)
< Smokey the Bar says, "Help stamp out software pirates" [squish!] > In article <452@mmintl.UUCP>, robg@mmintl.UUCP (Robert Goldman) writes: > > I am working on a program that needs to access the terminal in a pretty raw > state. In particular, it must have some way to tell whether there are any > keys in the input buffer waiting to be read. Is there some portable unix > call that responds with this information? > Robert Goldman, MultiMate International In Unix(tm) System III and V (all releases), you can ioctl() the line to have VMIN and VTIME set to 0; a read() will only get any characters in the input queue. (Note that ioctl(fd,TCFLSH,0) will flush the input queue.) More portably, you can fcntl() the file descriptor with O_NDELAY, which avoids blocking on tty's and pipes (and fifos). If you're always going to avoid blocking, you can open() the file with O_NDELAY. Both ioctl() and fcntl() are pretty cheap to call, so it's not too expensive to go back and forth. -- Unix is a trademark of some entity within AT&T, but I don't know what it's called this week. AT&T's Bell Labs? -- -Paul S. R. Chisholm The above opinions are my own, {pegasus,vax135}!lzwi!psc not necessarily those of any {mtgzz,ihnp4}!lznv!psc telecommunications company.
robg@mmintl.UUCP (Robert Goldman) (06/21/85)
I am very grateful to everyone on the net who responded to my
requests for information about unix terminal i/o. Here is a brief summary
of the information which I received.
The questions I asked were: what is curses? where is it
documented, and how does one get the documentation? what systems does it
work under? which terminals does it and does it not support? and how can
one read no-wait input off the terminal?
what is curses?
A terminal-independant i/o library for unix.
where is it documented, and how does one get the documentation?
this was the real toughie. the man page for curses gives the
following reference: SEE ALSO
_Screen_Updating_and_Cursor_Movement_Optimization:_A_Library_Package_, Ken
Arnold.
I had no luck getting hold of this. I called Bell labs, and they
didn't have it, I called UCB and they couldn't tell their tushies from their
elbows, and I finally gave up when I found curses documentation in a
friend's copy of the XENIX documentation. That's a pretty good source,
albeit cluttered by a ridiculous number of repetitions of the initials
"IBM." Here are some suggestions which others gave; I hope you have better
luck than I did:
It comes with BSD documentation (Volume 2c I think) and SVR2 (called
"curses/terminfo" in the Programmer's Guide). You can get SV doc by
calling 1-800-828-UNIX I believe.
Michael Baldwin
AT&T Bell Laboratories
another person (whose message I am embarrassed to admit that I lost),
suggested that I contact UCB, Corey Hall. Unfortunately, they were the
people who didn't know . . . In fact, UCB didn't seem to know where Corey
Hall WAS.
another person suggested that USENIX might have the documentation.
what systems does curses work under?
BSDs 4.1 and 4.2, SysV and Xenix. I don't know about the other
clones, but I imagine so.
what terminals does it support?
most people said that it supported every imaginable one.
how can one tell if there are keystrokes waiting to be interpreted? is there
a portable method?
To answer the second question first, NO. People sent me various
different methods for different unix versions. Here is a quick synopsis:
BSD 4.1 (mine):
use an ioctl call with the constant FIONREAD. This will tell how
many bytes are unread in a given file. (see man ioctl & man tty)
BSD 4.2:
as per above, or
Either use the same method as in 4.1BSD or use non-blocking reads.
# include <fcntl.h>
...
i = fcntl(0,F_GETFL, 0);
fcntl(0, F_SETFL, i | FNDELAY);
This makes reads non-blocking. If a read would block, it returns -1,
with EWOULDBLOCK in errno.
(from Ceriel Jacobs, Vrije Universiteit,
Amsterdam)
sysV and sysIII:
In these unix systems, non-blocking reads are also available, but are
a little different. I don't have the documentation on that, but I believe
the FNDELAY above, is called O_NDELAY here, and if a read would block,
it returns 0.
(also from Mr./Ms. Jacobs [sorry about that!])
older unices:
wierd. here are some tips from respondents:
There is no way to do it in V7 apart from poking
around /dev/kmem, which is not terribly portable.
Larry Wall
{allegra,burdvax,cbosgd,hplabs,ihnp4,sdcsvax}!sdcrdcf!lwall
-
V7: Officially impossible. If you have source, though, I can send
you the code for the FIONREAD call (see below), which is easy to
insert into a V7 kernel.
Also, there is a bug in the tty driver, allowing you to do this. It
works as follows:
If you set the mode to RAW or CBREAK, using the non-wait ioctl (TIOCSETN),
and there is still a line terminator in the input buffer (LF, or
whatever), whenever you read() after that, you will get end of file if
there is no char available. If you drop me a line at htsa!jack I'll
send you a code fragment.
Jack Jansen, jack@mcvax.UUCP
pwa-b!utah-gr!seismo!mcvax!jack (Jack Jansen)
-
Well, you can use a FIONREAD ioctl, but that is not portable.
The alternative is to send yourself an alarm, start a getchar(), and
if the alarm arrives before a character, continue on your merry way.
--
Don Davis
JHU/APL
...decvax!harpo!seismo!umcp-cs!aplvax!ded
...rlgvax!cvl!umcp-cs!aplvax!ded
Again, my greatest thanks to all of you who answered my query.
Robert Goldman
MultiMate International
None of the opinions above are binding on MultiMate, they are my own.
However, I imagine that MultiMate is officially grateful, as am I.jordan@ucbvax.ARPA (Jordan Hayes) (06/25/85)
In article <455@mmintl.UUCP> robg@mmintl.UUCP (Robert Goldman) writes: >where is it documented, and how does one get the documentation? > this was the real toughie. the man page for curses gives the >following reference: SEE ALSO >_Screen_Updating_and_Cursor_Movement_Optimization:_A_Library_Package_, Ken >Arnold. > I had no luck getting hold of this. I called Bell labs, and they >didn't have it, I called UCB and they couldn't tell their tushies from their >elbows, and I finally gave up when I found curses documentation in a >friend's copy of the XENIX documentation. The paper he mentions is available from the Academic Computing Services Library and Document Sales office, 218 Evans Hall, Berkeley, CA 94720 (415) 642-5205, or in the manual, or in the USENIX manual set (Programmer's manual, Supplementary Documents). >another person (whose message I am embarrassed to admit that I lost), >suggested that I contact UCB, Corey Hall. Unfortunately, they were the >people who didn't know . . . In fact, UCB didn't seem to know where Corey >Hall WAS. Hmmm. First of all, it's Cory Hall. Second of all, I guess you get what you pay for when you get free advice. Also, the AT&T (SYSV I guess) version was hacked (I hear by Mark Horton) so you may check into that before taking the Arnold paper verbatim... /jordan ------- ORAL: "...Hey! Jordan!..." ARPA: jordan@ucb-vax.BERKELEY.EDU UUCP: jordan@ucbvax.UUCP WARHEADS: 37' 52.29" N 122' 15.41" W
ttorgers@udenva.UUCP (Troy Torgerson) (07/10/85)
In article <> robg@mmintl.UUCP (Robert Goldman) writes: > > > > I am very grateful to everyone on the net who responded to my >requests for information about unix terminal i/o. Here is a brief summary >of the information which I received. > >where is it documented, and how does one get the documentation? > this was the real toughie. the man page for curses gives the >following reference: SEE ALSO >_Screen_Updating_and_Cursor_Movement_Optimization:_A_Library_Package_, Ken >Arnold. > I had no luck getting hold of this. I called Bell labs, and they >didn't have it, I called UCB and they couldn't tell their tushies from their >elbows, and I finally gave up when I found curses documentation in a >friend's copy of the XENIX documentation. That's a pretty good source, >albeit cluttered by a ridiculous number of repetitions of the initials >"IBM." Here are some suggestions which others gave; I hope you have better >luck than I did: >It comes with BSD documentation (Volume 2c I think) and SVR2 (called >"curses/terminfo" in the Programmer's Guide). You can get SV doc by >calling 1-800-828-UNIX I believe. > Michael Baldwin > AT&T Bell Laboratories I have SUaCMO:ALP by K. Arnold on our system. Try looking under /usr/doc/curses for a file called Curses.doc. Obviously, many of you don't have it, so If I get more than a couple requests, I'll post it. It is about 80 blocks unnroffed, so I'll wait to see if I get any requests for it. Troy Torgerson udenva!ttorgers