IO::Tty#

📦 std

Pseudo-terminals and the terminal constants: the compiled part under IO::Pty (a pty master and its slave as handles) and IO::Tty.

Synopsis#

use IO::Pty;
my $pty = IO::Pty->new;               # IO::Pty::pty_allocate
my $slave = $pty->slave;              # IO::Tty::_open_tty
print $pty->ttyname, "\n";            # e.g. /dev/pts/3

use IO::Tty qw(TIOCSWINSZ);           # IO::Tty::Constant
my $ws = IO::Tty::pack_winsize(24, 80);

How it works#

IO::Pty::pty_allocate returns a pty’s master and slave descriptors and the slave’s name, or an empty list. It tries posix_openpt, then getpt, openpty and /dev/ptmx, then the BSD-style /dev/pty?? names; for each master it grants and unlocks the slave, names it with ptsname_r or ptsname, opens it, and moves both descriptors above 2. With $IO::Tty::DEBUG true it says on stderr what it tries; with use warnings (category io) each method that fails warns. IO::Tty::_open_tty opens a terminal by name, ttyname names a handle’s terminal, and pack_winsize/unpack_winsize convert a struct winsize. Loading defines the constants of IO::Tty::Constant, undef for the ones this system lacks, and $IO::Tty::CONFIG.

This is a native implementation of Tty.xs of IO-Tty 1.31 as its Makefile.PL configures it on Linux, with the xssubs.c it writes; IO/Tty.pm, IO/Pty.pm and the IO/Tty/Constant.pm it writes are used unchanged.

Differences from upstream#

One, where perl 5.44 with Tty.xs crashes or reports memory it never wrote (t/81-xs-native/IO-Tty/150-or-better.t):

unpack_winsize of a value with no string - undef, a number, a reference - dies “Bad arg length - got 0, expected 8”. perl5 reads the length of a string that is not there: undef segfaults, and the others report a number from memory (“got 94515720394056”).

Modules#

IO::Tty::Constant - Terminal Constants (autogenerated)

Functions#

Pseudo-terminals#

`ttyname`#

The name of the terminal a handle is open on, or undef.

`pack_winsize`#

A struct winsize as a string, for the TIOCSWINSZ ioctl.

`unpack_winsize`#

The four numbers of a struct winsize string.

Synopsis

my ($rows, $cols, $xpixel, $ypixel) = IO::Tty::unpack_winsize($ws);

What you get back

Four numbers; a string that is not eight bytes long dies “IO::Tty::unpack_winsize(): Bad arg length - got N, expected 8”.