Read input from Keyboard, do not proceed if no input

Shell Programming and Scripting
1

Hi,

I am working on a script, which requests users to enter input.
Ex: read -p "Please enter your email id:" email

I don't want users skipping this entry, this has to be mandatory.I dont want to proceed without input.

I can do a check if variable $email is empty and proceed if not.But, i have around 20 inputs and it is hard to check on all the inputs and if user does not enter variable 19 i don't want to start from 1 again.

Please do the needful.

Thanks,
Aravind.

2

I'm afraid you'll have to do the hard work and validate every single input. Maybe using a function?

3

why don't you put the mandatory ones at the beginning? then throw into a while loop? this chokes off any continuation rather than repeating the loop.

4

If your idea of valid is just "not an empty string", you can loop on the request for each variable sequentially with something like:

while [ -z "$var1" ]
do	printf 'Enter variable 1 value: '
	read -r var1
	[ -z "$var1" ] && echo 'Variable 1 cannot be empty; try again.'
done
while [ -z "$var2" ]
do	printf 'Enter variable 2 value: '
	read -r var2
	[ -z "$var2" ] && echo 'Variable 2 cannot be empty; try again.'

done
...

instead of asking the user to enter all 20 variables and then verifying all of the values and restarting from the beginning if one of them had an error.

5

Don, why doing so much double effort?
Try:

#!/bin/bash
#
#	Variables
#
	# Expand the task list with words that describe the task
	declare TASK_LIST="name email"
	declare -A ANSWERS
#
#	Messages
#
	# Use the words from the task-list as string identifier
	MSG_STR_NAME="What is your name"
	MSG_STR_EMAIL="What is your email"
#
#	Action
#
	# Work the list
	for task in $TASK_LIST
	do
		# Prepare the message string
		str=MSG_STR_${task^^}
		# Loop while input is empty
		while [ -z "${ANSWERS[$task]}" ]
		do
			echo ${!str}
			read input
			ANSWERS[$task]=$input
		done
	done
#
#	Your work to do....
#
	echo
	echo "Result values are:"
	for item in $TASK_LIST
	do
		echo "$item :: ${ANSWERS[$item]}"
	done

Hope this helps

EDIT:
Looks for me like:

0 ~/tmp $ bash aravindadla 
What is your name
Simon
What is your email
something

Result values are:
name :: Simon
email :: something
6

Don/Sea,

Your options looks more feasible to me.
Will try them today and get back.

Thanks,
Aravind.

7

How about another approach in a recent shell (e.g. bash 4 )? Given file

First Name,FNAME  
Last Name,LNAME    
Birthday,BDAY

and a function declared as

getvar() { while [ ! ${!2} ]; do read -p "$1: " "$2"; done }

this would fill all the variables as requested with minor efforts.

while IFS=, read PR VAR <&3; do getvar "$PR" "$VAR"; echo $VAR"="${!VAR}; done 3< file
First Name: Joe
FNAME=Joe
Last Name: Miller
LNAME=Miller
Birthday: 12.7.88
BDAY=12.7.88

Add validations and/or error checking to taste.

8

As an addendum...

You will need to work out the error checking for each important field.

For example to gather the email address somebody.something@someaddress.extension you will have to check that it has a valid format. Not to forget that once passed it has to be checked for email validity too.
The above example is valid although does not exist but somebody.somethinATsomeaddress.extension is not.

Anything requiring a number only will have to be checked too although this should be staright forward.