[EMAIL PROTECTED] wrote:
> Hi Bob, a quick question if I could as I am trying to determine if my bash
> thinks it has a tty device or not and therefore is interactive or not.
Internally bash will use the libc isatty(3) routine to determine if
the input/output files are tty devices. In the shell these are
available in the 'test' operator as the '-t' file operator.
$ test -t 0 && echo input is a tty
$ test -t 1 && echo output is a tty
> I do use openpty to get a master/slave and associate the slave FD with the
> bash. I *think* my bash is interactive, because right after the "no job
> control" I get a bash prompt ([EMAIL PROTECTED]:/homelocation>).
The technique I have used is to look at $-, the option flags, and see
if 'i' is present there.
PS1 is set and $- includes I if bash is interactive, allowing a
shell script or a startup file to test this state.
Something like this works:
case $- in
*i*) echo shell is interactive ;;
esac
Other people prefer to use a test for PS1 such as this example.
test "${PS1+set}" = set && echo shell is interactive
Chet Ramey followed up with this information:
> > In general, this happens when bash thinks it's interactive but can't
> > obtain a handle to the controlling terminal that allows it to
> > manipulate the controlling terminal's process group. Since that's all
> > job control really is -- switching the terminal's process group
> > between processes -- bash turns off job control if it's not available.
> So it seems like it is interactive in that I am getting prompts, the only
> things I have seen not work are using less as an editor, and more recently
> noticed Ctrl-C (sent as a hex '03' to bash) does not seem to interrupt
> things.
It would be useful to see what 'stty -a' reports. That will dump the
current tty settings, if it is a tty. I will simulate not being on a
tty by redirecting from /dev/null.
$ stty -a </dev/null
stty: standard input: Inappropriate ioctl for device
On a valid tty it will dump the current settings.
$ stty -a
speed 38400 baud; rows 24; columns 80; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts
-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
> I was trying to find out what the default terminal parameters and window
> size are for openpty() as I am currently sending in NULLs for those. I
> tried sending in window size parameters of 24x80, 640x480pix but that
> didn't seem to make a difference to my "less" problem.
I am not familiar with openpty(). Perhaps someone else on the mailing
list will have information about that operation.
> So again, curious if it sounds like my bash shell is interactive. If it
> sounds so, then would appreciate any leads on how i might better find out
> why it is printing out the "no job control", so that maybe if I can rectify
> that, it might also rectify the "less" editing problem .. thanks ...
Sorry but I don't have any hints for you there. Personally I would
need to learn how setting up ptys is typically done these days, such
as by inspecting how 'xterm' or 'expect' or other such programs do
this. As I recall Marc Rochkind discusses this operation in detail in
his book "Advanced UNIX Programming" and therefore might be a good
reference. A lot of best practices have changed since the last time I
set up a master-slave pty pair and I only remember the old ways.
Bob
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