Using read to prompt for editable user input in Bash 3 Post: 302737119

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Top Forums Shell Programming and Scripting Using read to prompt for editable user input in Bash 3 Post 302737119 by Corona688 on Wednesday 28th of November 2012 11:33:47 AM

11-28-2012

Registered User

Hitting enter for the default value is what I tend to see done in these situations.

The other way, beyond bringing an external utility with you, would be to play funny games with the terminal device and handle all keystrokes by yourself:

Code:

#!/bin/bash

oldsettings=$(stty -g)

trap "stty $oldsettings" EXIT

readdefault() { # variable prompt default
        local POS="${#3}"
        local VALUE="$3"
        local C

        stty -icanon min 1 time 0 -icrnl -echo

        printf "%s" "$2$3"

        while true
        do
                C="$(dd bs=10 count=1 2> /dev/null)"

                [ -z "$C" ] && continue

                # Okay, you've got raw keystrokes.  Now you're on your own.
        done

        stty icanon
}

readdefault VAR "Enter something:" "qwerty"

I tried filling out more, but could not for the life of me get my terminal and tput to agree on what the 'backspace' key is, even though backspace works in my terminal.

Example partly from here.

You can see why what you're asking for really isn't trivial. It may be more straightforward to upgrade your shell.

Last edited by Corona688; 11-28-2012 at 01:54 PM..

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line

line(1) 						      General Commands Manual							   line(1)

NAME

       line - read one line from user input

SYNOPSIS

       timeout]

DESCRIPTION

       copies  one  line (up to a new-line) from the standard input and writes it on the standard output.  It returns an exit code of 1 on EOF and
       always prints at least a new-line.  It is often used within shell files to read from the user's terminal.

   Options
       recognizes the following command-line option:

	      Timeout after
			  timeout seconds where timeout is an integer value (if a non-integer value is specified, it is converted to  an  integer;
			  i.e.,  rounded down).  A blank is required between and the timeout argument.	This option is not documented in POSIX and
			  other industry standards, and should not be used in portable applications.

EXTERNAL INFLUENCES

   International Code Set Support
       Single- and multi-byte character code sets are supported.

EXAMPLES

       The following lines in a shell script prompt for a file name and display information about the file:

       To limit the response time to 10 seconds, use the form:

       then test for no response.  If no response occurs before timeout expires, a default behavior should be provided.

WARNINGS

       This command is likely to be withdrawn from X/Open standards. Applications using this command might not be portable to other vendors'  sys-
       tems. As an alternative is recommended.

SEE ALSO

       sh(1), read(2).

STANDARDS CONFORMANCE

																	   line(1)

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