1PTS(4)                     Linux Programmer's Manual                    PTS(4)
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NAME

6       ptmx, pts - pseudoterminal master and slave
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DESCRIPTION

9       The  file  /dev/ptmx  is a character file with major number 5 and minor
10       number 2, usually of mode 0666 and owner.group  of  root.root.   It  is
11       used to create a pseudoterminal master and slave pair.
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13       When  a  process opens /dev/ptmx, it gets a file descriptor for a pseu‐
14       doterminal master (PTM), and a pseudoterminal  slave  (PTS)  device  is
15       created  in  the  /dev/pts directory.  Each file descriptor obtained by
16       opening /dev/ptmx is an independent PTM with its  own  associated  PTS,
17       whose path can be found by passing the descriptor to ptsname(3).
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19       Before  opening  the  pseudoterminal  slave, you must pass the master's
20       file descriptor to grantpt(3) and unlockpt(3).
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22       Once both the pseudoterminal master and slave are open, the slave  pro‐
23       vides  processes  with an interface that is identical to that of a real
24       terminal.
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26       Data written to the slave is presented  on  the  master  descriptor  as
27       input.  Data written to the master is presented to the slave as input.
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29       In  practice, pseudoterminals are used for implementing terminal emula‐
30       tors such as xterm(1), in which data read from the pseudoterminal  mas‐
31       ter  is  interpreted by the application in the same way a real terminal
32       would interpret the data, and for  implementing  remote-login  programs
33       such  as  sshd(8), in which data read from the pseudoterminal master is
34       sent across the network to a client program that is connected to a ter‐
35       minal or terminal emulator.
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37       Pseudoterminals  can  also  be used to send input to programs that nor‐
38       mally refuse to read input from pipes (such as su(1), and passwd(1)).
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FILES

41       /dev/ptmx, /dev/pts/*
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NOTES

44       The Linux support for the above (known as UNIX 98  pseudoterminal  nam‐
45       ing)  is  done  using the devpts file system, that should be mounted on
46       /dev/pts.
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48       Before  this  UNIX  98  scheme,  master  pseudoterminals  were   called
49       /dev/ptyp0,  ...   and  slave  pseudoterminals /dev/ttyp0, ...  and one
50       needed lots of preallocated device nodes.
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SEE ALSO

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

56       This page is part of release 3.53 of the Linux  man-pages  project.   A
57       description  of  the project, and information about reporting bugs, can
58       be found at http://www.kernel.org/doc/man-pages/.
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62Linux                             2002-10-09                            PTS(4)
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