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Shell Programming and Scripting

How to set character limit on READ?

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# 1  
Old 12-10-2013
How to set character limit on READ?
Hello,
I created the following (snippet from larger code):

Code:
 echo -n "A1: "
 read A1

 VERIFY=$(echo -n $A1|wc -c)
 if [ $VERIFY -gt 8 ]; then
  echo -e "TOO MANY CHARACTERS"
 fi

 echo -n "A2: "
 read A2
 echo -n "A3: "
 read A3
 echo -e "Concat: $B1/$B2/$B3"

Basically what it does is it asks the user for values for A1, A2, and A3. The only catch is that character length cannot exceed 8. I think I have the validations, but even if they exceed 8, the value is stored. How can I make it so that conditions for A1 must be met before you proceed. The same character limit applies to A2 and A3.
Last edited by jl487; 12-10-2013 at 06:21 PM..
# 2  
Old 12-10-2013
Use an infinite while loop. Break from the loop when the condition is met.

Here is a sample code:
Code:
#!/bin/ksh

while :
do
        print "A1: "
        read A1
        [ ${#A1} -le 8 ] && break
done

Use shell builtin to get variable length instead of wc
# 3  
Old 12-10-2013
Quote:
Originally Posted by Yoda
Use an infinite while loop. Break from the loop when the condition is met.

Here is a sample code:
Code:
#!/bin/ksh

while :
do
        print "A1: "
        read A1
        [ ${#A1} -le 8 ] && break
done

Use shell builtin to get variable length instead of wc
Thanks for the suggestion. Unfortunately, I have this in a bash script, so I'm trying to use bash.
# 4  
Old 12-10-2013
That was just an example. Use bash instead, replace print with printf:
Code:
#!/bin/bash

while :
do
        printf "%s" "A1: "
        read A1
        [ ${#A1} -le 8 ] && break
done

This User Gave Thanks to Yoda For This Post:
jl487
# 5  
Old 12-11-2013
Could truncating it be a valid choice? If so, using typeset might be usful:-
Code:
typeset -L8 A1
read A1?"Please enter a string: "

You might end up with trailing blanks of the input is less that 8 characters though. Is that acceptable?
Code:
$ typeset -L8 A1 
$ read A1?"Please enter a string: "
Please enter a string: greatbiglongstring             
$ echo "!$A1!"                     
!greatbig!
$ read A1?"Please enter a string: "
Please enter a string: Hello
$ echo "!$A1!"                     
!Hello   !



I hope that this helps,
Robin
Liverpool/Blackburn
UK
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