This is a very simple program o illustrate how pty(3)s work.
It allows us to emulate old, text based terminals which run at low
baud speeds. When you use it, the terminal speed you configure with
stty(1) is commited and the terminal begins to output characters at
the speed mandated by the baud rate configured. You'll see it
sending characters as baudrate mandates and see the screen updates
at low speed as they happened to be once upon a time.
As it is so simple to build it with make(1), I have not considered
appropiate to embed it into autoconf(1), automake(1) and/or
autohead(1) utils, so you have to compile it using FreeBSD
specific flags.
To compile on FreeBSD, just issue the command
make CFLAGS=-DHAS_LIBUTIL_H=1 install
in the source code directory. The program will be installed by
default in ${HOME}/bin. If you want to install it in the
/usr/local hierarchy (or elsewhere), just uncomment in the
Makefile the UMOD=... line and then, issue the command:
make prefix="/usr/local" CFLAGS=-DHAS_LIBUTIL_H=1 install
and you'll have it installed properly.
SLOWTTY(1) - FreeBSD General Commands Manual
slowtty - a program to simulate baudrates of old ttys over networked lines.
slowtty [-dltw] [-b bufsize] [command [arguments ...]]
The slowtty takes a pseudo-tty and simulates on it the behaviour of a slow tty line, by using the configured baudrate, and character frame length to calculate the character transmission time and adapt the output to it, so characters flow at a fixed pace as the serial line would do.
While you are running the slowtty command, all the settings made with the stty(1) utility that result in changes in the baudrate or character size, parity or the like, will be taken into account by slowtty and will be obeyed to simulate changes in the line configuration.
If you don't add any command to the parameter list, the slowtty utility just spawns a shell (as specified by the $SHELL environment variable.) The shell can be made a login shell with the option -l (see below)
-b
Allows to set the internal buffer size used to read characters from the slave tty. Normally this is adjusted dynamically so no more than one second characters get buffered on output. The idea is to allow for ^C characters to be processed without having to print lots of buffered characters, while allowing for high speeds to allow to process the buffer in chunks to maintain the average stream flow.
-d
This flag makes the slowtty program verbose, outputting log lines to stderr about what it is doing. It is useful for debugging purposes.
-l
prependeds a - to the program name argument in the command to execute. This, when used with a shell command, has the effect of making the shell a login shell, so it will execute the login scripts and do user session initialization as if a normal login has been done.
-t
With this option, slowtty does not use tcsetattr(3) to set the master terminal attributes, neither it passes the settings on the master to the slave pty.
-w
Makes slowtty not transmit the window size attributes to the slave tty, so the program run is not aware of terminal window size changes.
Luis Colorado <luiscoloradourcola@gmail.com>
- August 8, 2019