Manpage of PTS

PTS

Section: Linux Programmer's Manual (4)
Updated: 2016-03-15
Index
 

NAME

ptmx, pts - pseudoterminal master and slave  

DESCRIPTION

The file /dev/ptmxis a character file with major number 5 and minor number 2, usually of mode 0666 and owner.group of root.root. It is used to create a pseudoterminal master and slave pair.

When a process opens /dev/ptmx, it gets a file descriptor for a pseudoterminal master (PTM), and a pseudoterminal slave (PTS) device is created in the /dev/ptsdirectory. Each file descriptor obtained by opening /dev/ptmxis an independent PTM with its own associated PTS, whose path can be found by passing the file descriptor to ptsname(3).

Before opening the pseudoterminal slave, you must pass the master's file descriptor to grantpt(3) and unlockpt(3).

Once both the pseudoterminal master and slave are open, the slave provides processes with an interface that is identical to that of a real terminal.

Data written to the slave is presented on the master file descriptor as input. Data written to the master is presented to the slave as input.

In practice, pseudoterminals are used for implementing terminal emulators such as xterm(1), in which data read from the pseudoterminal master is interpreted by the application in the same way a real terminal would interpret the data, and for implementing remote-login programs such as sshd(8), in which data read from the pseudoterminal master is sent across the network to a client program that is connected to a terminal or terminal emulator.

Pseudoterminals can also be used to send input to programs that normally refuse to read input from pipes (such as su(1), and passwd(1)).  

FILES

/dev/ptmx, /dev/pts/* 

NOTES

The Linux support for the above (known as UNIX 98 pseudoterminal naming) is done using the devptsfilesystem, that should be mounted on /dev/pts.

Before this UNIX 98 scheme, master pseudoterminals were called /dev/ptyp0, ... and slave pseudoterminals /dev/ttyp0, ... and one needed lots of preallocated device nodes.  

SEE ALSO

getpt(3), grantpt(3), ptsname(3), unlockpt(3), pty(7)


 

Index

NAME
DESCRIPTION
FILES
NOTES
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 22:28:01 GMT, June 20, 2016