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DESCRIPTION top. A pseudoterminal (sometimes abbreviated "pty") is a pair of virtual character devices that provide a bidirectional communication channel. One end of the channel is called the master; the other end is called the slave.
The tty command of terminal basically prints the file name of the terminal connected to standard input. tty is short of teletype, but popularly known as a terminal it allows you to interact with the system by passing on the data (you input) to the system, and displaying the output produced by the system.
TTY ports are direct connections to the computer such as a keyboard/mouse or a serial connection to the device. PTS connections are SSH connections or telnet connections. All of these connections can connect to a shell which will allow you to issue commands to the computer.
A pseudo-TTY is a pair of character special files, a master file and a corresponding slave file. The master file is used by a networking application such as OMVS or rlogin. The corresponding slave file is used by the shell or the user's process to read and write terminal data.
"tty" originally meant "teletype" and "pty" means "pseudo-teletype".
In UNIX, /dev/tty* is any device that acts like a "teletype", ie, a terminal. (Called teletype because that's what we had for terminals in those benighted days.)
A pty is a pseudotty, a device entry that acts like a terminal to the process reading and writing there, but is managed by something else. They first appeared (as I recall) for X Window and screen and the like, where you needed something that acted like a terminal but could be used from another program.
A tty is a terminal (it stands for teletype - the original terminals used a line printer for output and a keyboard for input!). A terminal is a basically just a user interface device that uses text for input and output.
A pty is a pseudo-terminal - it's a software implementation that appears to the attached program like a terminal, but instead of communicating directly with a "real" terminal, it transfers the input and output to another program.
For example, when you ssh in to a machine and run ls, the ls command is sending its output to a pseudo-terminal, the other side of which is attached to the SSH daemon.
tty: teletype. Usually refers to the serial ports of a computer, to which terminals were attached.
pty: pseudoteletype. Kernel provided pseudoserial port connected to programs emulating terminals, such as xterm, or screen.
If you run the mount command with no command-line arguments, which displays the file systems mounted on your system, you’ll notice a line that looks something like this: none on /dev/pts type devpts (rw,gid=5,mode=620) This indicates that a special type of file system, devpts , is mounted at /dev/pts .This file system, which isn’t associated with any hardware device, is a “magic” file system that is created by the Linux kernel. It’s similar to the /proc file system
Like the /dev directory, /dev/pts contains entries corresponding to devices. But unlike /dev , which is an ordinary directory, /dev/pts is a special directory that is cre- ated dynamically by the Linux kernel.The contents of the directory vary with time and reflect the state of the running system. The entries in /dev/pts correspond to pseudo-terminals (or pseudo-TTYs, or PTYs).
Linux creates a PTY for every new terminal window you open and displays a corre- sponding entry in /dev/pts .The PTY device acts like a terminal device—it accepts input from the keyboard and displays text output from the programs that run in it. PTYs are numbered, and the PTY number is the name of the corresponding entry in /dev/pts .
For example, if the new terminal window’s PTY number is 7, invoke this command from another window: % echo ‘I am a virtual di ’ > /dev/pts/7 The output appears in the new terminal window.
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