UNIX for Advanced & Expert Users

#!/bin/bash
bash --version
uname -a
status=0
KEYBOARD()
{
	read -r -p "Enter QUIT or EXIT to quit:- " kbinput
	if [ "$kbinput" == "QUIT" ] || [ "$kbinput" == "EXIT" ]
	then
		status=255
		break
	fi
	if [ "$kbinput" == "TEST" ]
	then
		echo "Hello World!"
	fi
}
while true
do
	echo "This will loop and hold until keyboard input is quitted."
	KEYBOARD
done
echo "you are here..."

Last login: Wed May 24 16:37:36 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> ./kb_loop.sh
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin16)
Copyright (C) 2007 Free Software Foundation, Inc.
Darwin Barrys-MBP 16.6.0 Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64 x86_64
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- TEST
Hello World!
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- QUIT
you are here...
AMIGA:amiga~/Desktop/Code/Shell> _

mint@mint ~ $ chmod 755 kb_loop.sh
mint@mint ~ $ ./kb_loop.sh
GNU bash, version 4.3.42(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Linux mint 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- TEST
Hello World!
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- QUIT
you are here...
mint@mint ~ $ _

To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details.

ubuntu@ubuntu:~$ chmod 755 kb_loop.sh
ubuntu@ubuntu:~$ ./kb_loop.sh
GNU bash, version 4.4.5(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Linux ubuntu 4.10.0-19-generic #21-Ubuntu SMP Thu Apr 6 17:04:57 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- TEST
Hello World!
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- QUIT
./kb_loop.sh: line 11: break: only meaningful in a `for', `while', or `until' loop
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- _

while KEYBOARD
do
...
done

KEYBOARD()
{
	read -r -p "Enter QUIT or EXIT to quit:- " kbinput || return 1

	if [ "$kbinput" == "QUIT" ] || [ "$kbinput" == "EXIT" ]
	then
                return 1 # Nonzero return will break while loop
	elif [ "$kbinput" == "TEST" ]
	then
		echo "Hello World!"
	fi

        return 0 # Zero return will not break while loop
}

KEYBOARD()
{
	read -r -p "Enter QUIT or EXIT to quit:- " kbinput || return 1

        case "$kbinput" in
        QUIT|EXIT)        return 1 ;;
        TEST)        echo "Hello World" ;;
        esac

        return 0
}

$ shellcheck z7

In z7 line 4:
status=0
^-- SC2034: status appears unused. Verify it or export it.


In z7 line 10:
                status=255
                ^-- SC2034: status appears unused. Verify it or export it.


In z7 line 11:
                break
                ^-- SC2104: In functions, use return instead of break.

OS, ker|rel, machine: Linux, 3.16.0-4-amd64, x86_64
Distribution        : Debian 8.7 (jessie) 
bash GNU bash 4.3.30

shellcheck      analyse shell scripts (man)
Path    : /usr/bin/shellcheck
Version : ShellCheck - shell script analysis tool
Type    : ELF 64-bit LSB executable, x86-64, version 1 (SYSV ...)
Help    : probably available with -h
Repo    : Debian 8.7 (jessie) 
Home    : http://hackage.haskell.org/package/ShellCheck (pm)

#!/bin/bash
bash --version
uname -a
status=0
KEYBOARD()
{
	read -r -p "Enter QUIT or EXIT to quit:- " kbinput
	if [ "$kbinput" == "QUIT" ] || [ "$kbinput" == "EXIT" ]
	then
		status=255
		break
	fi
	if [ "$kbinput" == "TEST" ]
	then
		echo "Hello World!"
	fi
}
while true
do
	echo "This will loop and hold until keyboard input is quitted."
	KEYBOARD
done
echo "You are here..."
echo "Status = $status..."

Last login: Fri May 26 09:45:32 on ttys000
AMIGA:barrywalker~> chmos 755 test.sh
-bash: chmos: command not found
AMIGA:barrywalker~> chmod 755 test.sh
AMIGA:barrywalker~> ./test.sh
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin16)
Copyright (C) 2007 Free Software Foundation, Inc.
Darwin Patricias-iMac.local 16.6.0 Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64 x86_64
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- TEST
Hello World!
This will loop and hold until keyboard input is quitted.
Enter QUIT or EXIT to quit:- EXIT
You are here...
Status = 255...
AMIGA:barrywalker~> _

Last login: Sat May 27 10:20:46 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> cat kb_loop2.sh
#!/usr/local/bin/dash
# This passes the ShellCheck test as /bin/sh.
TEXT="Thank you Corona688."
status=0
KEYBOARD()
{
	printf "Enter QUIT to quit:- "
	read -r kbinput
	if [ "$kbinput" = "QUIT" ]
	then
		TEXT="YOU ARE HERE!"
		status=255
		echo "Exiting the KEYBOARD() function..."
                return 1
	elif [ "$kbinput" = "TEST" ]
	then
		echo "Hello World!"
	fi
        return 0
}
# Main loop...
while true
do
	echo "This will loop and hold until keyboard input is quitted."
	KEYBOARD
	if [ $? -eq 1 ]
	then
		break
	fi
done
echo "Now outside the loop..."
echo "$TEXT"
echo "Status = $status..."
AMIGA:amiga~/Desktop/Code/Shell> 
AMIGA:amiga~/Desktop/Code/Shell> 
AMIGA:amiga~/Desktop/Code/Shell> ./kb_loop2.sh
This will loop and hold until keyboard input is quitted.
Enter QUIT to quit:- NOTHING
This will loop and hold until keyboard input is quitted.
Enter QUIT to quit:- TEST
Hello World!
This will loop and hold until keyboard input is quitted.
Enter QUIT to quit:- QUIT
Exiting the KEYBOARD() function...
Now outside the loop...
YOU ARE HERE!
Status = 255...
AMIGA:amiga~/Desktop/Code/Shell> _