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.Dd $Mdocdate: April 20 2017 $ .Dt OPENPTY 3 .Os .Sh NAME .Nm getptmfd , .Nm openpty , .Nm fdopenpty , .Nm login_tty , .Nm forkpty , .Nm fdforkpty .Nd tty utility functions .Sh SYNOPSIS n termios.h n util.h .Ft int .Fn getptmfd "void" .Ft int .Fn openpty "int *amaster" "int *aslave" "char *name" "const struct termios *termp" "const struct winsize *winp" .Ft int .Fn fdopenpty "int ptmfd" "int *amaster" "int *aslave" "char *name" "const struct termios *termp" "const struct winsize *winp" .Ft int .Fn login_tty "int fd" .Ft pid_t .Fn forkpty "int *amaster" "char *name" "const struct termios *termp" "const struct winsize *winp" .Ft pid_t .Fn fdforkpty "int ptmfd" "int *amaster" "char *name" "const struct termios *termp" "const struct winsize *winp" .Sh DESCRIPTION The .Fn openpty , .Fn login_tty , and .Fn forkpty functions perform manipulations on ttys and pseudo-ttys.
p The .Fn openpty function finds an available pseudo-tty and returns file descriptors for the master and slave in .Fa amaster and .Fa aslave . If .Fa name is non-null, the filename of the slave is returned in .Fa name (a string of at least 16 characters). If .Fa termp is non-null, the terminal parameters of the slave will be set to the values in .Fa termp . If .Fa winp is non-null, the window size of the slave will be set to the values in .Fa winp .
p The .Fn openpty function allocates the pseudo-tty through the
a /dev/ptm device (see .Xr pty 4 for details) which means that its ownership is changed to the UID of the caller, permissions are set to correct values, and all earlier uses of that device are revoked (see .Xr revoke 2 for details).
p The .Fn fdopenpty and .Fn fdforkpty functions work like .Fn openpty and .Fn forkpty but expect a
a /dev/ptm file descriptor .Fa ptmfd obtained from the .Fn getptmfd function.
p The .Fn login_tty function prepares for a login on the tty .Fa fd (which may be a real tty device, or the slave of a pseudo-tty as returned by .Fn openpty ) by creating a new session, making .Fa fd the controlling terminal for the current process, setting .Fa fd to be the standard input, output, and error streams of the current process, and closing .Fa fd .
p The .Fn forkpty function combines .Fn openpty , .Fn fork , and .Fn login_tty to create a new process operating in a pseudo-tty. The file descriptor of the master side of the pseudo-tty is returned in .Fa amaster , and the filename of the slave in .Fa name if it is non-null. The .Fa termp and .Fa winp parameters, if non-null, will determine the terminal attributes and window size of the slave side of the pseudo-tty. .Sh RETURN VALUES If a call to .Fn openpty , .Fn login_tty , or .Fn forkpty is not successful, -1 is returned and .Va errno is set to indicate the error. Otherwise, .Fn openpty , .Fn login_tty , and the child process of .Fn forkpty return 0, and the parent process of .Fn forkpty returns the process ID of the child process. .Sh FILES l -tag -width /dev/tty[p-zP-T][0-9a-zA-Z]x -compact t Pa /dev/pty[p-zP-T][0-9a-zA-Z] master pseudo terminals t Pa /dev/tty[p-zP-T][0-9a-zA-Z] slave pseudo terminals t Pa /dev/ptm pseudo terminal management device .El .Sh ERRORS .Fn getptmfd may fail and set .Va errno for any of the errors specified for the routine .Xr open 2 .
p .Fn openpty and .Fn fdopenpty will fail if: l -tag -width Er t Bq Er ENOENT There are no available ttys. .El
p .Fn fdopenpty and .Fn fdforkpty will fail if .Fn getptmfd fails. .Fn forkpty and .Fn fdforkpty will fail if either .Fn openpty or .Fn fork fails.
p .Fn login_tty will fail if .Fn ioctl fails to set .Fa fd to the controlling terminal of the current process. .Sh SEE ALSO .Xr fork 2 , .Xr revoke 2 , .Xr pty 4