check length content existence of variable

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# 1  
Old 07-21-2009
check length content existence of variable

hi guys, im learning so be gentle...

i'm wanting to write a script to read in a customer number.

in order that the code is robust i want to check

1) the length of the value entered (4 characters)
2) that all characters entered are numeric between the values 1 to 3
3) that a value is entered

could anyone give me a few pointers to the commans/systax i will need to use for each check?

also any idea if any of them can be combined?

any pointers welcome...


# 2  
Old 07-21-2009
If have prompted the customer for their number and read it in thus:
read -p "Please enter you customer number: " RESP

I'll leave some else who can test for digits more elegantly than I.

Then to check they have entered anything at all you can do:
if [ -n "${RESP}" ]; then
  echo "You answered ${RESP}."

if [ -z "${RESP}" ]; then
  echo "You have not entered anything, please try again."

To check how many characters have been entered do:
LENGTH=`echo ${RESP} | wc -c`

if [ ${LENGTH} -ge 10 ]; then
  echo "The number entered is too long."

if [ ${LENGTH} -le 8 ]; then
  echo "The number entered is too short."

Note that wc -c counts the new line character, so adds one to the length you are expecting.
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