COMMENT(!MOD!zsh/zpty
A builtin for starting a command in a pseudo-terminal.
!MOD!)
The tt(zsh/zpty) module offers one builtin:

startitem()
findex(zpty)
item(tt(zpty) [ tt(-e) ] [ tt(-b) ] var(name) [ var(arg ...) ])(
The arguments following var(name) are concatenated with spaces between,
then executed as a command, as if passed to the tt(eval) builtin.  The
command runs under a newly assigned pseudo-terminal; this is useful for
running commands non-interactively which expect an interactive
environment.  The var(name) is not part of the command, but is used to
refer to this command in later calls to tt(zpty).

With the tt(-e) option, the pseudo-terminal is set up so that input
characters are echoed.

With the tt(-b) option, input to and output from the pseudo-terminal are
made non-blocking.
)
item(tt(zpty) tt(-d) [ var(names) ... ])(
The second form, with the tt(-d) option, is used to delete commands
previously started, by supplying a list of their var(name)s.  If no
var(names) are given, all commands are deleted.  Deleting a command causes
the HUP signal to be sent to the corresponding process.
)
item(tt(zpty) tt(-w) [ tt(-n) ] var(name) [ var(strings ...) ])(
The tt(-w) option can be used to send the to command var(name) the given
var(strings) as input (separated by spaces).  If the tt(-n) option is
em(not) given, a newline is added at the end.

If no var(strings) are provided, the standard input is copied to the
pseudo-terminal; this may stop before copying the full input if the
pseudo-terminal is non-blocking.

Note that the command under the pseudo-terminal sees this input as if it
were typed, so beware when sending special tty driver characters such as
word-erase, line-kill, and end-of-file.
)
item(tt(zpty) tt(-r) [ tt(-mt) ] var(name) [ var(param) [ var(pattern) ] ])(
The tt(-r) option can be used to read the output of the command var(name).
With only a var(name) argument, the output read is copied to the standard
output.  Unless the pseudo-terminal is non-blocking, copying continues
until the command under the pseudo-terminal exits; when non-blocking, only
as much output as is immediately available is copied.  The return status is
zero if any output is copied.

When also given a var(param) argument, at most one line is read and stored
in the parameter named var(param).  Less than a full line may be read if
the pseudo-terminal is non-blocking.  The return status is zero if at least
one character is stored in var(param).

If a var(pattern) is given as well, output is read until the whole string
read matches the var(pattern), even in the non-blocking case.  The return
status is zero if the string read matches the pattern, or if the command
has exited but at least one character could still be read.  If the option
tt(-m) is present, the return status is zero only if the pattern matches.
As of this writing, a maximum of one megabyte of output can be consumed
this way; if a full megabyte is read without matching the pattern, the
return status is non-zero.

In all cases, the return status is non-zero if nothing could be read, and
is tt(2) if this is because the command has finished.

If the tt(-r) option is combined with the tt(-t) option, tt(zpty) tests
whether output is available before trying to read.  If no output is
available, tt(zpty) immediately returns the status tt(1).  When used
with a var(pattern), the behaviour on a failed poll is similar to
when the command has exited:  the return value is zero if at least
one character could still be read even if the pattern failed to match.
)
item(tt(zpty) tt(-t) var(name))(
The tt(-t) option without the tt(-r) option can be used to test
whether the command var(name) is still running.  It returns a zero
status if the command is running and a non-zero value otherwise.
)
item(tt(zpty) [ tt(-L) ])(
The last form, without any arguments, is used to list the commands
currently defined.  If the tt(-L) option is given, this is done in the
form of calls to the tt(zpty) builtin.
)
enditem()
