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Full Discussion: Problem reading terminal response string from Zsh
Top Forums Shell Programming and Scripting Problem reading terminal response string from Zsh Post 303010561 by rovf on Wednesday 3rd of January 2018 07:33:00 AM
Old 01-03-2018
Problem reading terminal response string from Zsh
Note: This posting is related to my posting at bash - Reading answer to control string sent to xterm - Stack Overflow , but I could get there a solution only for bash. I can use that solution, but for curiosity, I wonder, whether I could do this in Zsh as well.

The problem is to send a (Posix-) terminal query string to the terminal where the (interactive) shell is running, and to read the response from the terminal. For example, when we send Escape followed by the letter Z, the terminal is supposed to respond with the terminal ID. This response also starts with an Escape, followed by an arbitrary number of characters. Since I don't know the number of characters returned in advance, I have to accumulate them one by one.

This is the solution I achieved with bash, ask_tty.sh:

Code:
#!/bin/bash

str='' # Buffer for response
tty=$(tty)

# Send query string to terminal. Example: Esc Z queries for terminal id
echo -e '\e'${1:-Z}  >$tty

# Read response from terminal
while :
do
  read -rs -t 1 -n 1 <$tty
  if [[ -z $REPLY ]]
  then
    break
  fi
  str="${str}$REPLY"
done

# Output response without leading Esc
echo "${str#?}"

If I run in my terminal either ask_tty.sh Z or ask_tty.sh (because I made Z the default value), I get as response on stdout

[?63;1;2;4;6;9;15;22;29c

The actual reading of each character is done by read -rs -t 1 -n 1 <$tty.

I feel that for adapting this solution to Zsh, I have to change the bash read to an equivalent Zsh read, but I could not get it done: Either the command hangs, or it returns only the first character of the answer string. For instance, I tried read -rs -t -k and read -rs -t 1 -k 1.

How can I solve this in Zsh?

Update: I'm using Zsh 5.3 (given the evolution of Zsh, version might matter here), running on Cygwin.
Last edited by rovf; 01-03-2018 at 09:46 AM.. Reason: Providing additional information
 

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LEARN ABOUT OPENSOLARIS

shells

shells(4)							   File Formats 							 shells(4)

NAME

       shells - shell database

SYNOPSIS

       /etc/shells

DESCRIPTION

       The shells file contains a list of the shells on the system. Applications use this file to determine whether a shell is valid. See getuser-
       shell(3C). For each shell a single line should be present, consisting of the shell's path, relative to root.

       A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by  the  routines
       which search the file. Blank lines are also ignored.

       The following default shells are used by utilities: /bin/bash, /bin/csh, /bin/jsh, /bin/ksh, /bin/ksh93, /bin/pfcsh, /bin/pfksh, /bin/pfsh,
       /bin/sh, /bin/tcsh, /bin/zsh, /sbin/jsh, /sbin/sh, /usr/bin/bash, /usr/bin/csh, /usr/bin/jsh, /usr/bin/ksh, /usr/bin/ksh93, /usr/bin/pfcsh,
       /usr/bin/pfksh, /usr/bin/pfsh, and /usr/bin/sh, /usr/bin/tcsh, /usr/bin/zsh, and /usr/sfw/bin/zsh. /etc/shells overrides the default list.

       Invalid shells in /etc/shells could cause unexpected behavior, such as being unable to log in by way of ftp(1).

FILES

       /etc/shells    list of shells on system

SEE ALSO

       vipw(1B), ftpd(1M), sendmail(1M), getusershell(3C), aliases(4)

SunOS 5.11							    20 Nov 2007 							 shells(4)
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