Syntax error checking whether account number is numeric

Question

if [[ ${account_nr} =~ ^[0-9]+$ &&  ${from_account_nr} =~ ^[0-9]+$ ]]

This is intended to check whether the account number is numeric or not. I

Answer 1

A space is required between if and [:

$ account_num=1234
$ if [[ ${accoun_num} =~ ^[0-9]+$ ]] ; then echo "foo" ; fi
foo
$

Also, this works fine in bash:

$ account_nr=1234
$ from_account_nr=9876
$ if [[ ${account_nr} =~ ^[0-9]+$ && ${from_account_nr} =~ ^[0-9]+$ ]] ; then echo "foo" ; fi
foo
$

You cannot have spaces around your shell variable assignments, either. Below is a correction to your latest version:

jai="CNM"
hanuman="BRK"
if [[ $jai =~ ^[0-9]+$ && $hanuman =~ ^[0-9]+$  ]]
then
  echo "Jai hanuman"
  echo "valid input"
fi

Since neither jai or hanuman are numbers, the above script runs and outputs nothing. If you set them both to a number, then it will display:

Jai hanuman
valid input

Note that if you put a space, like so:

jai = "CNM"

Then the shell (bash) thinks you are executing a command called jai and you get the error indicated.