posix_openpt(3c)

1posix_openpt(3C)         Standard C Library Functions         posix_openpt(3C)
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NAME

6       posix_openpt - open a pseudo terminal device
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SYNOPSIS

9       #include <stdlib.h>
10       #include <fcntl.h>
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12       int posix_openpt(int oflag);
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DESCRIPTION

16       The  posix_openpt()  function establishes a connection between a master
17       device for a pseudo-terminal and a file descriptor. The file descriptor
18       is used by other I/O functions that refer to that pseudo-terminal.
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21       The  file  status flags and file access modes of the open file descrip‐
22       tion are set according to the value of oflag.
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25       Values for oflag are constructed by a  bitwise-inclusive  OR  of  flags
26       from the following list, defined in <fcntl.h>.
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28       O_RDWR      Open for reading and writing.
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31       O_NOCTTY    If  set,  posix_openpt() does not cause the terminal device
32                   to become the controlling terminal for the process.
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36       The behavior of other values for the oflag argument is unspecified.
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RETURN VALUES

39       Upon successful completion, the posix_openpt() function opens a  master
40       pseudo-terminal  device and returns a non-negative integer representing
41       the lowest numbered unused file descriptor. Otherwise, -1  is  returned
42       and errno is set to indicate the error.
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ERRORS

45       The posix_openpt() function will fail if:
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47       EMFILE    {OPEN_MAX} file descriptors are currently open in the calling
48                 process.
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51       ENFILE    The maximum allowable number of files is  currently  open  in
52                 the system.
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56       The posix_openpt() function may fail if:
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58       EINVAL    The value of oflag is not valid.
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61       EAGAIN    Out of pseudo-terminal resources.
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64       ENOSR     Out of STREAMS resources.
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EXAMPLES

68       Example 1 Open a pseudo-terminal.
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71       The  following  example opens a pseudo-terminal and returns the name of
72       the slave device and a file descriptor.
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75         #include fcntl.h>
76         #include stdio.h>
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78         int masterfd, slavefd;
79         char *slavedevice;
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81         masterfd = posix_openpt(O_RDWR|O_NOCTTY);
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83         if (masterfd == -1
84               || grantpt (masterfd) == -1
85               || unlockpt (masterfd) == -1
86               || (slavedevice = ptsname (masterfd)) == NULL)
87               return -1;
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89         printf("slave device is: %s\n", slavedevice);
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91         slavefd = open(slave, O_RDWR|O_NOCTTY);
92         if (slavefd < 0)
93               return -1;
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USAGE

97       This function provides a method for portably obtaining a file  descrip‐
98       tor  of a master terminal device for a pseudo-terminal. The grantpt(3C)
99       and ptsname(3C) functions can be used to manipulate mode and  ownership
100       permissions and to obtain the name of the slave device, respectively.
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ATTRIBUTES

103       See attributes(5) for descriptions of the following attributes:
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108       ┌─────────────────────────────┬─────────────────────────────┐
109       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
110       ├─────────────────────────────┼─────────────────────────────┤
111       │Interface Stability          │Standard                     │
112       ├─────────────────────────────┼─────────────────────────────┤
113       │MT-Level                     │MT-Safe                      │
114       └─────────────────────────────┴─────────────────────────────┘
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