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Full Discussion: Controlling user input
Top Forums Shell Programming and Scripting Controlling user input Post 303038255 by Don Cragun on Thursday 29th of August 2019 12:07:31 AM
Old 08-29-2019
Quote:
Originally Posted by Chubler_XL
Since you specify using bash shell we can flush the input buffer using:

Code:
while read -rs -N 1 -t 0.1 2> /dev/null ; do : ; done

so your script would look like this:

Code:
#!/bin/bash

for i in 1 2 3; do
 echo "Ready?"
 sleep 2
 mpg123 $i.mp3
 echo "Ok now you can respond. Press 1 if you liked it, 2 if you didn't."
 while read -rs -N 1 -t 0.1 2> /dev/null ; do : ; done
 read -n 1 RESPONSE
done

Hi Chubler_XL,
That might work with some versions of bash, but it won't work with 3.2.57 (which comes with the most recent release of macOS Mojave) since the read built-in in that version doesn't have a -N option. The loop you suggest above silently throws away the diagnostic saying there is no -N option and gives no indication that whatever was intended to be done by the while loop didn't do anything. The following read then reads the next available character no matter when it was typed.

Since darwin_866 has told us neither what OS is being used nor which version of bash is being used, we don't have any way to know if what you suggested might work in his/her environment.

Cheers,
Don
 

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WHICH(1)						      General Commands Manual							  WHICH(1)

NAME
which - shows the full path of (shell) commands. SYNOPSIS
which [options] [--] programname [...] DESCRIPTION
Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been exe- cuted when this argument had been entered at the shell prompt. It does this by searching for an executable or script in the directories listed in the environment variable PATH using the same algorithm as bash(1). This man page is generated from the file which.texinfo. OPTIONS
--all, -a Print all matching executables in PATH, not just the first. --read-alias, -i Read aliases from stdin, reporting matching ones on stdout. This is useful in combination with using an alias for which itself. For example alias which='alias | which -i'. --skip-alias Ignore option `--read-alias', if any. This is useful to explicity search for normal binaries, while using the `--read-alias' option in an alias or function for which. --read-functions Read shell function definitions from stdin, reporting matching ones on stdout. This is useful in combination with using a shell func- tion for which itself. For example: which() { declare -f | which --read-functions $@ } export -f which --skip-functions Ignore option `--read-functions', if any. This is useful to explicity search for normal binaries, while using the `--read-functions' option in an alias or function for which. --skip-dot Skip directories in PATH that start with a dot. --skip-tilde Skip directories in PATH that start with a tilde and executables which reside in the HOME directory. --show-dot If a directory in PATH starts with a dot and a matching executable was found for that path, then print "./programname" rather than the full path. --show-tilde Output a tilde when a directory matches the HOME directory. This option is ignored when which is invoked as root. --tty-only Stop processing options on the right if not on tty. --version,-v,-V Print version information on standard output then exit successfully. --help Print usage information on standard output then exit successfully. RETURN VALUE
Which returns the number of failed arguments, or -1 when no `programname' was given. EXAMPLE
The recommended way to use this utility is by adding an alias (C shell) or shell function (Bourne shell) for which like the following: [ba]sh: which () { (alias; declare -f) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@ } export -f which [t]csh: alias which 'alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde' This will print the readable ~/ and ./ when starting which from your prompt, while still printing the full path when used from a script: > which q2 ~/bin/q2 > echo `which q2` /home/carlo/bin/q2 BUGS
The HOME directory is determined by looking for the HOME environment variable, which aborts when this variable doesn't exist. Which will consider two equivalent directories to be different when one of them contains a path with a symbolic link. AUTHOR
Carlo Wood <carlo@gnu.org> SEE ALSO
bash(1) WHICH(1)
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