Finding whitespaces in string variable shell script-CodePudding

I have a string variable which could have values like below.

my_string=" "
my_string="   "
my_string="name1"
my_string="name 2"

I have to identify if my_string has only spaces/whitespaces and exit the program when it has only whitespaces. If it has one or two spaces inbetween, it's a valid string.

How to check if the string has only whitespaces and exit the shell script based on that.

Thank you.

CodePudding user response：

Your question is somewhat unclear. However the following example should point you in the right direction.

#!/bin/sh

#my_string=""
my_string="     "
#my_string="   "
#my_string="name1"
#my_string="name 2"

case "$my_string" in
  "")             echo "string is empty";;
  *[![:space:]]*) echo "string does not contain only whitespace";;
  *)              echo "string contains only whitespace"; exit 1;;
esac

If you want to test only for spaces and tabs rather than all whitespace, you should use [:blank:] instead of [:space:].

CodePudding user response：

Since you are searching for a solution in POSIX shell, I would do something like this:

if [ "$(echo $my_string | tr -d ' ')" = '' ]
then
  echo The string is blank
fi