Manual Pages for UNIX Operating System command usage for man posix_openpt

Standard C Library Functions                     posix_openpt(3C)



NAME
     posix_openpt - open a pseudo terminal device

SYNOPSIS
     #include 
     #include 

     int posix_openpt(int oflag);


DESCRIPTION
     The posix_openpt() function establishes a connection between
     a master device for a pseudo-terminal and a file descriptor.
     The file descriptor is used  by  other  I/O  functions  that
     refer to that pseudo-terminal.


     The file status flags and file access modes of the open file
     description are set according to the value of oflag.


     Values for oflag are constructed by a  bitwise-inclusive  OR
     of flags from the following list, defined in .

     O_RDWR      Open for reading and writing.


     O_NOCTTY    If set, posix_openpt() does not cause the termi-
                 nal  device  to  become the controlling terminal
                 for the process.



     The behavior of other  values  for  the  oflag  argument  is
     unspecified.

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

ERRORS
     The posix_openpt() function will fail if:

     EMFILE    {OPEN_MAX} file descriptors are currently open  in
               the calling process.


     ENFILE    The maximum allowable number of files is currently
               open in the system.



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Standard C Library Functions                     posix_openpt(3C)



     The posix_openpt() function may fail if:

     EINVAL    The value of oflag is not valid.


     EAGAIN    Out of pseudo-terminal resources.


     ENOSR     Out of STREAMS resources.


EXAMPLES
     Example 1 Open a pseudo-terminal.


     The following example opens a  pseudo-terminal  and  returns
     the name of the slave device and a file descriptor.


       #include fcntl.h>
       #include stdio.h>

       int masterfd, slavefd;
       char *slavedevice;

       masterfd = posix_openpt(O_RDWR|O_NOCTTY);

       if (masterfd == -1
             || grantpt (masterfd) == -1
             || unlockpt (masterfd) == -1
             || (slavedevice = ptsname (masterfd)) == NULL)
             return -1;

       printf("slave device is: %s\n", slavedevice);

       slavefd = open(slave, O_RDWR|O_NOCTTY);
       if (slavefd < 0)
             return -1;


USAGE
     This function provides a method  for  portably  obtaining  a
     file  descriptor  of  a master terminal device for a pseudo-
     terminal. The grantpt(3C) and ptsname(3C) functions  can  be
     used  to  manipulate  mode  and ownership permissions and to
     obtain the name of the slave device, respectively.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:





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Standard C Library Functions                     posix_openpt(3C)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


SEE ALSO
     open(2),  grantpt(3C),  ptsname(3C),  unlockpt(3C),   attri-
     butes(5), standards(5)









































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