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Date: Tue, 19 May 2020 19:54:13 +0100
From: Stephane Chazelas <stephane@chazelas.org>
To: Daniel Shahaf <d.s@daniel.shahaf.name>
Cc: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: [PATCH] [doc] clone module using xterm's slave mode
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	Zsh hackers list <zsh-workers@zsh.org>
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 <20200519010140.38c12d2b@tarpaulin.shahaf.local2>
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In-Reply-To: <20200519010140.38c12d2b@tarpaulin.shahaf.local2>

2020-05-19 01:01:40 +0000, Daniel Shahaf:
[...]
> There's a race condition here («clone» might run before «./pty» is
> created).  Is it worthwhile to point it out in the text, or add
> a «sleep» in the example?
[...]

You're right, maybe a better approach would be to supply a
contrib function for that which could be extended to other
terminal emulators like:

clone_on_new_terminal() {
  local terminal_cmd setup
  case $1 in
    (*xterm*)
      terminal_cmd="$1 -Sunused/3"
      setup='IFS= read -r WINDOWID'
      ;;
    (*rxvt*)
      terminal_cmd="$1 -pty-fd 3"
      setup=
      ;;
    (*)
      printf >&2 '"%s" terminal not supported\n' "$1"
      return 1
      ;;
  esac
      
  socat -d -d PTY,wait-slave,echo=0 "exec:$terminal_cmd,nofork,fdout=3,fdin=3" 2>&1 | {
    local -a fields
    IFS=' ' read -rA fields
    clone $fields[-1]
    if (($!)); then
      cat >&2
    else
      eval "$setup"
    fi
  }
}

Still a bit brittle as it relies on a specific output format of
socat's debug output. 

> By the way, WDYT of adding a concept index entry (e.g., «cindex(tty,
> cloning the shell onto an unused)») at the top of the file?  I think the
> existing cindex entries won't help someone who doesn't know what the
> module is called to discover it.
[...]

To be honest, I'm not sure I understand what that module is for.

What would be a typical use case?

-- 
Stephane