.\"
.TH PTY 7 2005-10-10 "Linux" "Linux Programmer's Manual"
.SH NAME
-pty \- pseudo-terminal interfaces
+pty \- pseudoterminal interfaces
.SH DESCRIPTION
-A pseudo-terminal is a pair of virtual character devices that
+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
.IR master ;
the other end is called the
.IR slave .
-The slave end of the pseudo-terminal provides an interface
+The slave end of the pseudoterminal provides an interface
that behaves exactly like a classical terminal.
A process that expects to be connected to a terminal,
-can open the slave end of a pseudo-terminal and
+can open the slave end of a pseudoterminal and
then be driven by a program that has opened the master end.
Anything that is written on the master end is provided to the process
on the slave end as though it was input typed on a terminal.
to be generated for the foreground process group
that is connected to the slave.
Conversely, anything that is written to the slave end of the
-pseudo-terminal can be read by the process that is connected to
+pseudoterminal can be read by the process that is connected to
the master end.
-Pseudo-terminals are used by applications such as network login services
+Psuedoterminals are used by applications such as network login services
.RB ( ssh "(1), " rlogin "(1), " telnet (1)),
terminal emulators,
.BR script (1),
and
.BR expect (1).
-Historically, two pseudo-terminal APIs have evolved: BSD and System V.
-SUSv1 standardized a pseudo-terminal API based on the System V API,
+Historically, two pseudoterminal APIs have evolved: BSD and System V.
+SUSv1 standardized a pseudoterminal API based on the System V API,
and this API should be employed in all new programs that use
-pseudo-terminals.
+pseudoterminals.
Linux provides both BSD-style and (standardized) System V-style
-pseudo-terminals.
-System V-style terminals are commonly called Unix 98 pseudo-terminals
+pseudoterminals.
+System V-style terminals are commonly called UNIX 98 pseudoterminals
on Linux systems.
-Since kernel 2.6.4, BSD-style pseudo-terminals are considered deprecated
+Since kernel 2.6.4, BSD-style pseudoterminals are considered deprecated
(they can be disabled when configuring the kernel);
-Unix 98 pseudo-terminals should be used in new applications.
-.SS "Unix 98 pseudo-terminals"
-An unused Unix 98 pseudo-terminal master is opened by calling
+UNIX 98 pseudoterminals should be used in new applications.
+.SS "UNIX 98 pseudoterminals"
+An unused UNIX 98 pseudoterminal master is opened by calling
.BR posix_openpt (3).
(This function opens the master clone device,
.IR /dev/ptmx ;
.BR open (2).
The Linux kernel imposes a limit on the number of available
-Unix 98 pseudo-terminals.
+UNIX 98 pseudoterminals.
In kernels up to and including 2.6.3, this limit is configured
at kernel compilation time
.RB ( CONFIG_UNIX98_PTYS ),
-and the permitted number of pseudo-terminals can be up to 2048,
+and the permitted number of pseudoterminals can be up to 2048,
with a default setting of 256.
Since kernel 2.6.4, the limit is dynamically adjustable via
.IR /proc/sys/kernel/pty/max ,
and a corresponding file,
.IR /proc/sys/kernel/pty/nr ,
-indicates how many pseudo-terminals are currently in use.
+indicates how many pseudoterminals are currently in use.
For further details on these two files, see
.BR proc (5).
-.SS "BSD pseudo-terminals"
-BSD-style pseudo-terminals are provided as precreated pairs, with
+.SS "BSD pseudoterminals"
+BSD-style pseudoterminals are provided as precreated pairs, with
names of the form
.I /dev/ptyXY
(master) and
(slave),
where X is a letter from the 16-character set [p-za-e],
and Y is a letter from the 16-character set [0-9a-f].
-(The precise range of letters in these two sets varies across Unix
+(The precise range of letters in these two sets varies across UNIX
implementations.)
For example,
.I /dev/ptyp1
and
.I /dev/ttyp1
-constitute a BSD pseudo-terminal pair.
-A process finds an unused pseudo-terminal pair by trying to
+constitute a BSD pseudoterminal pair.
+A process finds an unused pseudoterminal pair by trying to
.BR open (2)
-each pseudo-terminal master until an open succeeds.
-The corresponding pseudo-terminal slave (substitute "tty"
+each pseudoterminal master until an open succeeds.
+The corresponding pseudoterminal slave (substitute "tty"
for "pty" in the name of the master) can then be opened.
.SH "FILES"
.I /dev/ptmx
-(Unix 98 master clone device)
+(UNIX 98 master clone device)
.br
.I /dev/pts/*
-(Unix 98 slave devices)
+(UNIX 98 slave devices)
.br
.I /dev/pty[p-za-e][0-9a-f]
(BSD master devices)
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