A '''terminal''' is a display unit that is part of the user interface to a
computer system. The word carries the connotation of being text-only.
** See Also **
[ANSI]: Various ANSI standards govern terminal behaviour.
[xterm]: A terminal emulator.
[curses]: A [C] library for controlling terminals.
[handling of ANSI terminals using Expect]:
[pty]: Short for '''pseudo teletype''', but commonly referred to as '''pseudo terminal'''
[stty]: The [Units%|%*nix] command to configure and manage a terminal.
[terminal control sequence]:
** Reference **
[http://vt100.net/%|%VT100.net]: Dedicated to the range of video terminals produced by Digital Equipment Corporation (DEC) from 1970 to 1995. The most famous of these is the VT100.
[http://www.linusakesson.net/programming/tty/index.php%|%The TTY demystified], Linus Åkesson, 2008-07-25:
** Description **
Terminal emulators for [Linux] have support for ANSI escape codes built in.
** Checking for a Terminal **
`[chan configure]` can be used to determine whether a channel is connecte to a terminal:
======
proc isatty chan {
expr {[catch {chan configure $chan -mode}] == 0}
}
======
Credit to [http://www.sqlite.org/src/info/559835e54e0715f2b4d207d056199a8268af739e] for the idea.
However, this doesn't work on [Microsoft Windows%|%Windows].
[AMG]: To check if stdin is connected to a terminal, run:
======
if {![catch {exec /usr/bin/tty -s}]} {
# stdin is a terminal
}
======
Checking for stdout/stderr is harder because `[exec]` does not allow stdout/stderr to be redirected to stdin because stdout/stderr are not considered readable. Instead, let the shell do the redirection. Furthermore, instruct [[exec]] to not intercept stdout/stderr.
======
if {![catch {exec /bin/sh -c {/usr/bin/tty -s < /dev/stdout} >@ stdout}]} {
# stdout is a terminal
}
if {![catch {exec /bin/sh -c {/usr/bin/tty -s < /dev/stderr} 2>@ stderr}]} {
# stderr is a terminal
}
======
Without the `-s` switch, the tty program not only checks if its stdin is a terminal, but it also prints the device name to its stdout, e.g. `/dev/pts/0`.
----
[MHo] 2021-09-17: How to test this on Windows? I found the following way if [twapi] is available:
======
package require twapi
twapi::import_commands
proc isStdinRedirected {} {
catch {get_tcl_channel_handle stdin write}
}
puts [isStdinRedirected]
======
Examples:
======
c:\Users\matthiasu\usr\pgm\tcl\usr\Tst\isatty>echo test|tclkitsh test8.tcl
1
c:\Users\matthiasu\usr\pgm\tcl\usr\Tst\isatty>tclkitsh test8.tcl<nul
1
c:\Users\matthiasu\usr\pgm\tcl\usr\Tst\isatty>tclkitsh test8.tcl
0
======
----
Tcl internally uses `isatty()`. Perhaps it could provide the following command:
======
chan isatty ...
======
** Page Authors **
[amg]: Provided the example of `[chan configure]` to check for a terminal.
[pyk]:
<<categories>> Text Screen