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| .TH POSIX_OPENPT 3 2021-03-22 "" "Linux Programmer's Manual" |
| .SH NAME |
| posix_openpt \- open a pseudoterminal device |
| .SH SYNOPSIS |
| .nf |
| .B #include <stdlib.h> |
| .B #include <fcntl.h> |
| .PP |
| .BI "int posix_openpt(int " flags ");" |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR posix_openpt (): |
| .nf |
| _XOPEN_SOURCE >= 600 |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR posix_openpt () |
| function opens an unused pseudoterminal master device, returning a |
| file descriptor that can be used to refer to that device. |
| .PP |
| The |
| .I flags |
| argument is a bit mask that ORs together zero or more of |
| the following flags: |
| .TP |
| .B O_RDWR |
| Open the device for both reading and writing. |
| It is usual to specify this flag. |
| .TP |
| .B O_NOCTTY |
| Do not make this device the controlling terminal for the process. |
| .SH RETURN VALUE |
| On success, |
| .BR posix_openpt () |
| returns a file descriptor (a nonnegative integer) which is the lowest |
| numbered unused file descriptor. |
| On failure, \-1 is returned, and |
| .I errno |
| is set to indicate the error. |
| .SH ERRORS |
| See |
| .BR open (2). |
| .SH VERSIONS |
| Glibc support for |
| .BR posix_openpt () |
| has been provided since version 2.2.1. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR posix_openpt () |
| T} Thread safety MT-Safe |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .PP |
| .BR posix_openpt () |
| is part of the UNIX 98 pseudoterminal support (see |
| .BR pts (4)). |
| .SH NOTES |
| Some older UNIX implementations that support System V |
| (aka UNIX 98) pseudoterminals don't have this function, but it |
| can be easily implemented by opening the pseudoterminal multiplexor device: |
| .PP |
| .in +4n |
| .EX |
| int |
| posix_openpt(int flags) |
| { |
| return open("/dev/ptmx", flags); |
| } |
| .EE |
| .in |
| .PP |
| Calling |
| .BR posix_openpt () |
| creates a pathname for the corresponding pseudoterminal slave device. |
| The pathname of the slave device can be obtained using |
| .BR ptsname (3). |
| The slave device pathname exists only as long as the master device is open. |
| .SH SEE ALSO |
| .BR open (2), |
| .BR getpt (3), |
| .BR grantpt (3), |
| .BR ptsname (3), |
| .BR unlockpt (3), |
| .BR pts (4), |
| .BR pty (7) |