Compare string length to a number

Shell Programming and Scripting
1

Hi,
I want to compare strings length to a number but i am getting error. I want first name should be length of 8.
Please help.

#bin !/bin/bash
clear
echo -n "Enter name "
read name
IFS=_
ary=($name)
for key in "${!ary[@]}"; do echo "$key${ary[$key]}"; done
##First name should be equal to 8 digits
var=${ary[0]}
l1=${#var}
echo "$l1"
if [ "$l1" == 8]
then 
echo "Length Matching"
else
echo "Not Matching"
if
2

Hello rajneesh4U,

As a starter, could you please change if [ "$l1" == 8] to if [[ "$l1" == 8 ]] and let us know how it goes then(Not tested complete script though).

Thanks,
R. Singh

3

Hi,
Still code is showing same error. I have changed below code as per your suggestion, but still not working.

#bin !/bin/bash
clear
echo -n "Enter name "
read name
IFS=_
ary=($name)
for key in "${!ary[@]}"; do echo "$key${ary[$key]}"; done
##First name should be equal to 8 digits
var=${ary[0]}
l1=${#var}

echo "$l1"

if [ ["$l1" == 8]]
then 
echo "Length Matching"
else
echo "Not Matching"
if
4

Merely posting that there are errors is not helping much.

  1. What errors do you get on running this script?
  2. What did you understand from the errors?
1 Like
5

Hi.

Does this help?

#!/bin/bash
#bin !/bin/bash
# clear
set -x
echo -n "Enter name "
read name
IFS=_
ary=($name)
for key in "${!ary[@]}"; do echo "$key${ary[$key]}"; done
##First name should be equal to 8 digits
var=${ary[0]}
l1=${#var}
echo "$l1"
if [ "$l1" == 8 ]
then 
echo "Length Matching"
else
echo "Not Matching"
# if
fi

See man bash for questions.

Bestr wishes ... cheers, drl

6

You jumped from the frying pan into the fire. if [ ["$l1" == 8]] is as wrong as if [ "$l1" == 8] is.

  • either needs a space after the 8
  • integer comparisons should be done with the -eq operator. While results are identical for single digit numbers, 100 would compare below 20 for string operations.
  • there should NOT be any space between the [[ .

Try

if [ "$l1" -eq 8 ]

or

[[ "$l1" -eq 8 ]]

.

1 Like
7

If you want to do what is in the comments:

##First name should be equal to 8 digits

case $var in 
  ([0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9])
    echo "The first part of name equals 8 digits"
  ;;
  (*)
    echo "The first part of name does not equal 8 digits"
esac

instead of $var you could also use ${name_*%%}

Or you could use:

case $name in 
  ([0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]_)
   echo "The first part of name equals 8 digits"
  ;;
  (*)
    echo "The first part of name does not equal 8 digits"
esac
1 Like
8

Hi.

Needing to compare $var to the pattern of digits, so could be:

if [[ "$var" =~ [0-9]{8} ]]

Best wishes ... cheers, drl

1 Like
9

In that case regex anchors would need to be used to ensure it begins with digits and/or that it is precisely 8 digits long..
for example (in recent bash / ksh93):

if [[ $var =~ ^[0-9]{8}$ ]]

or

if [[ $name =~ ^[0-9]{8}_ ]]
1 Like