1OPENPTY(3)                 Linux Programmer's Manual                OPENPTY(3)
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NAME

6       openpty, login_tty, forkpty - tty utility functions
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SYNOPSIS

9       #include <pty.h>
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11       int openpty(int *amaster, int *aslave, char *name,
12                   const struct termios *termp,
13                   const struct winsize *winp);
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15       pid_t forkpty(int *amaster, char *name,
16                     const struct termios *termp,
17                     const struct winsize *winp);
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19       #include <utmp.h>
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21       int login_tty(int fd);
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23       Link with -lutil.
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DESCRIPTION

26       The  openpty()  function finds an available pseudo-terminal and returns
27       file descriptors for the master and slave in amaster  and  aslave.   If
28       name  is  not  NULL, the filename of the slave is returned in name.  If
29       termp is not NULL, the terminal parameters of the slave will be set  to
30       the values in termp.  If winp is not NULL, the window size of the slave
31       will be set to the values in winp.
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33       The login_tty() function prepares for a login on the tty fd (which  may
34       be  a real tty device, or the slave of a pseudo-terminal as returned by
35       openpty()) by creating a new session, making fd the controlling  termi‐
36       nal  for the calling process, setting fd to be the standard input, out‐
37       put, and error streams of the current process, and closing fd.
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39       The forkpty() function combines openpty(), fork(2), and login_tty()  to
40       create a new process operating in a pseudo-terminal.  The file descrip‐
41       tor of the master side of the pseudo-terminal is returned  in  amaster,
42       and the filename of the slave in name if it is not NULL.  The termp and
43       winp arguments, if not NULL, will determine the terminal attributes and
44       window size of the slave side of the pseudo-terminal.
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RETURN VALUE

47       If a call to openpty(), login_tty(), or forkpty() is not successful, -1
48       is returned and  errno  is  set  to  indicate  the  error.   Otherwise,
49       openpty(),  login_tty(),  and  the child process of forkpty() return 0,
50       and the parent process of forkpty() returns the process ID of the child
51       process.
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ERRORS

54       openpty() will fail if:
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56       ENOENT There are no available ttys.
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58       login_tty()  will  fail  if ioctl(2) fails to set fd to the controlling
59       terminal of the calling process.
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61       forkpty() will fail if either openpty() or fork(2) fails.
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CONFORMING TO

64       These are BSD functions, present in libc5 and  glibc2.   They  are  not
65       standardized in POSIX.
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NOTES

68       The  const  modifiers  were added to the structure pointer arguments of
69       openpty() and forkpty() in glibc 2.8.
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71       In versions of glibc before 2.0.92, openpty() returns file  descriptors
72       for  a  BSD pseudo-terminal pair; since glibc 2.0.92, it first attempts
73       to open a Unix 98 pseudo-terminal pair, and falls back to opening a BSD
74       pseudo-terminal pair if that fails.
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BUGS

77       Nobody  knows  how much space should be reserved for name.  So, calling
78       openpty() or forkpty() with non-NULL name may not be secure.
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SEE ALSO

81       fork(2), ttyname(3), pty(7)
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COLOPHON

84       This page is part of release 3.25 of the Linux  man-pages  project.   A
85       description  of  the project, and information about reporting bugs, can
86       be found at http://www.kernel.org/doc/man-pages/.
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90GNU                               2010-06-13                        OPENPTY(3)
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