unlockpt(3)		    Library Functions Manual		     unlockpt(3)

NAME
     unlockpt - unlock a pseudoterminal master/slave pair

LIBRARY
     Standard C library (libc, -lc)

SYNOPSIS
     #define _XOPEN_SOURCE
     #include <stdlib.h>

     int unlockpt(int fd);

 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

     unlockpt():
	 Since glibc 2.24:
	     _XOPEN_SOURCE >= 500
	 glibc 2.23 and earlier:
	     _XOPEN_SOURCE

DESCRIPTION
     The unlockpt() function unlocks the slave pseudoterminal device correspond-
     ing to the master pseudoterminal referred to by the file descriptor fd.

     unlockpt() should be called before opening the slave side of a pseudotermi-
     nal.

RETURN VALUE
     When  successful,	unlockpt() returns 0.  Otherwise, it returns -1 and sets
     errno to indicate the error.

ERRORS
     EBADF  The fd argument is not a file descriptor open for writing.

     EINVAL
	    The fd argument is not associated with a master pseudoterminal.

ATTRIBUTES
     For an explanation of the terms used in this  section,  see  attributes(7).
     allbox; lbx lb lb l l l.  Interface Attribute Value T{ unlockpt()
     T}	  Thread safety	  MT-Safe

STANDARDS
     POSIX.1-2008.

HISTORY
     glibc 2.1.	 POSIX.1-2001.

SEE ALSO
     grantpt(3), posix_openpt(3), ptsname(3), pts(4), pty(7)

Linux man-pages 6.18		   2025-09-21			     unlockpt(3)