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All Rights Reserved. 44.\" Portions Copyright (c) 2003, Sun Microsystems, Inc. All Rights Reserved. 45.\" Copyright 2022 Oxide Computer Company 46.\" 47.Dd February 5, 2022 48.Dt POSIX_OPENPT 3C 49.Os 50.Sh NAME 51.Nm posix_openpt 52.Nd open a pseudo-terminal manager device 53.Sh SYNOPSIS 54.In stdlib.h 55.In fcntl.h 56.Ft int 57.Fo posix_openpt 58.Fa "int oflag" 59.Fc 60.Sh DESCRIPTION 61The 62.Fn posix_openpt 63function establishes a connection between a manager device for a 64pseudo-terminal and a file descriptor. 65The file descriptor is used by other I/O functions that refer to that 66pseudo-terminal. 67.Pp 68The file status flags and file access modes of the open file description are 69set according to the value of 70.Fa oflag . 71.Pp 72Values for 73.Fa oflag 74are constructed by a bitwise-inclusive OR of flags from 75the following list, defined in 76.Xr fcntl.h 3HEAD : 77.Bl -tag -width Ds 78.It Dv O_RDWR 79Open for reading and writing. 80.It Dv O_NOCTTY 81If set, 82.Fn posix_openpt 83does not cause the terminal device to become the controlling terminal for the 84process. 85.El 86.Pp 87The behavior of other values for the 88.Fa oflag 89argument is unspecified. 90.Sh RETURN VALUES 91The 92.Fn posix_getopt 93function opens a manager pseudo-terminal device and, if successful, returns a 94non-negative integer representing the lowest numbered unused file descriptor ; 95otherwise, the value 96.Sy -1 97is returned and the global variable 98.Va errno 99is set to indicate the error. 100.Sh EXAMPLES 101.Sy Example 1 102Open a pseudo-terminal. 103.Pp 104The following example opens a pseudo-terminal and returns the name of the 105subsidiary device and a file descriptor. 106.Bd -literal -offset Ds 107#include <fcntl.h> 108#include <stdio.h> 109#include <err.h> 110 111int managerfd, subsidiaryfd; 112char *subsidiarydevice; 113 114if ((managerfd = posix_openpt(O_RDWR|O_NOCTTY)) < 0) { 115 err(1, "opening pseudo-terminal manager"); 116} 117 118if (grantpt(managerfd) != 0 || 119 unlockpt(managerfd) != 0 || 120 (subsidiarydevice = ptsname(managerfd)) == NULL) { 121 (void) close(managerfd); 122 err(1, "locating pseudo-terminal subsidiary"); 123} 124 125printf("subsidiary device is: %s\en", subsidiarydevice); 126 127if ((subsidiaryfd = open(subsidiary, O_RDWR|O_NOCTTY)) < 0) { 128 err(1, "opening pseudo-terminal subsidiary"); 129} 130.Ed 131.Sh ERRORS 132The 133.Fn posix_openpt 134function will fail if: 135.Bl -tag -width Er 136.It Er EMFILE 137.Brq Dv OPEN_MAX 138file descriptors are currently open in the calling process. 139.It Er ENFILE 140The maximum allowable number of files is currently open in the system. 141.El 142.Pp 143The 144.Fn posix_openpt 145function may fail if: 146.Bl -tag -width Er 147.It Er EINVAL 148The value of 149.Fa oflag 150is not valid. 151.It Er EAGAIN 152The system has run out of pseudo-terminal resources. 153.It Er ENOSR 154The system has run out of STREAMS resources. 155.El 156.Sh USAGE 157This function provides a portable method for obtaining the file descriptor of a 158manager terminal device for a pseudo-terminal, as opposed to using 159.Xr open 2 160on the 161.Xr ptm 4D 162device which is system-specific. 163.Pp 164The 165.Xr grantpt 3C 166function can be used to manipulate the mode and ownership permissions 167of the subsidiary device. 168The 169.Xr ptsname 3C 170function can be used to obtain the name of the subsidiary device. 171.Sh INTERFACE STABILITY 172.Sy Committed 173.Sh MT LEVEL 174.Sy MT-Safe 175.Sh SEE ALSO 176.Xr open 2 , 177.Xr grantpt 3C , 178.Xr ptsname 3C , 179.Xr unlockpt 3C , 180.Xr ptm 4D , 181.Xr pts 4D , 182.Xr attributes 7 , 183.Xr standards 7 184