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$FreeBSD: releng/10.2/lib/libc/stdlib/ptsname.3 240412 2012-09-12 17:54:09Z emaste $
.Dd August 20, 2008 .Dt PTSNAME 3 .Os .Sh NAME .Nm grantpt , .Nm ptsname , .Nm unlockpt .Nd pseudo-terminal access functions .Sh LIBRARY .Lb libc .Sh SYNOPSIS n stdlib.h .Ft int .Fn grantpt "int fildes" .Ft "char *" .Fn ptsname "int fildes" .Ft int .Fn unlockpt "int fildes" .Sh DESCRIPTION The .Fn grantpt , .Fn ptsname , and .Fn unlockpt functions allow access to pseudo-terminal devices. These three functions accept a file descriptor that references the master half of a pseudo-terminal pair. This file descriptor is created with .Xr posix_openpt 2 .
p The .Fn grantpt function is used to establish ownership and permissions of the slave device counterpart to the master device specified with .Fa fildes . The slave device's ownership is set to the real user ID of the calling process, and the permissions are set to user readable-writable and group writable. The group owner of the slave device is also set to the group .Dq Li tty .
p The .Fn ptsname function returns the full pathname of the slave device counterpart to the master device specified with .Fa fildes . This value can be used to subsequently open the appropriate slave after .Xr posix_openpt 2 and .Fn grantpt have been called.
p The .Fn unlockpt function clears the lock held on the pseudo-terminal pair for the master device specified with .Fa fildes . .Sh RETURN VALUES .Rv -std grantpt unlockpt
p The .Fn ptsname function returns a pointer to the name of the slave device on success; otherwise a .Dv NULL pointer is returned. .Sh ERRORS The .Fn grantpt , .Fn ptsname and .Fn unlockpt functions may fail and set .Va errno to: l -tag -width Er t Bq Er EBADF .Fa fildes is not a valid open file descriptor. t Bq Er EINVAL .Fa fildes is not a master pseudo-terminal device. .El
p In addition, the .Fn grantpt function may set .Va errno to: l -tag -width Er t Bq Er EACCES The slave pseudo-terminal device could not be accessed. .El .Sh SEE ALSO .Xr posix_openpt 2 , .Xr pts 4 , .Xr tty 4 .Sh STANDARDS The .Fn ptsname function conforms to .St -p1003.1-2008 .
p This implementation of .Fn grantpt and .Fn unlockpt does not conform to .St -p1003.1-2008 , because it depends on .Xr posix_openpt 2 to create the pseudo-terminal device with proper permissions in place. It only validates whether .Fa fildes is a valid pseudo-terminal master device. Future revisions of the specification will likely allow this behaviour, as stated by the Austin Group. .Sh HISTORY The .Fn grantpt , .Fn ptsname and .Fn unlockpt functions appeared in .Fx 5.0 .