wc -c gives me one extra character count

Question

So I made a script that adds users to the system, and I wanted to force the length of the usernames to 8 characters or below.

#!/bin/bash
# Only works if you're root

for ((a=1;a>0;a)); do
 if [[ "$UID" -eq 0 ]]; then
  echo "Quit this shit anytime by pressing CTRL + C"
  read -p 'Enter one usernames: ' USERNAME
  nrchar=$(echo ${USERNAME} | wc -c)
  echo $nrchar
  spcount=$(echo ${USERNAME} | tr -cd ' ' | wc -c)
  echo $spcount
  if [[ "${nrchar}" -ge 8 ]]; then
    echo "You may not have more than 8 characters in the username"
   elif [[ "${spcount}" -gt 0 ]]; then
    echo "The username may NOT contain any spaces"
   else
     read -p 'Enter one names of user: ' COMMENT
     read -s -p 'Enter one passwords of user: ' PASSWORD
     useradd -c "${COMMENT}" -m ${USERNAME}
     echo ${PASSWORD} | passwd --stdin ${USERNAME}
     passwd -e ${USERNAME}
   fi
 echo "------------------------------------------------------"
 else
  echo "You're not root, so GTFO!"
  a=0
 fi
done

That's the full script, but I think the problem is only here somewhere:

  read -p 'Enter one usernames: ' USERNAME
  nrchar=$(echo ${USERNAME} | wc -c)
  echo $nrchar

So the problem with this is, whenever I enter a 8 character username, the nrchar variable seems to always add one more character to it, as so:

[vagrant@localhost vagrant]$ sudo ./exercise2-stuffs.sh
Quit this shit anytime by pressing CTRL + C
Enter one usernames: userdoi1
9
0
You may not have more than 8 characters in the username
------------------------------------------------------
Quit this shit anytime by pressing CTRL + C
Enter one usernames: ^C
[vagrant@localhost vagrant]$ 

Even if I leave it blank, it still somehow counts one character:

[vagrant@localhost vagrant]$ sudo !.
sudo ./exercise2-stuffs.sh
Quit this shit anytime by pressing CTRL + C
Enter one usernames:
1
0
Enter one names of user:

How to identify this problem?

Answer 1

Even if I leave it blank, it still somehow counts one character [. . .] Could somebody please help me identify this problem?

Try printf instead of echo

$ echo "" | wc -m
1
$ printf "" | wc -m
0

Using echo, wc will count a newline character.

Or, perhaps better, use pure Bash without piping to wc:

$ string=foobar
$ echo "${#string}"
6

Answer 2

I would prefer the shell's "parameter expansion" method as well; but if you use wc, you could use its word count option as well:

read LENGTH WORDS REST <<<$(echo -n ${USERNAME} | wc -cw)
echo $LENGTH $WORDS 
2 8

You may want to make sure only ASCII characters are used - no multibyte international characters.

Should you go the bash internals path, the check for spaces could be

[ "$USERNAME" = "${USERNAME%% *}" ] && echo No spaces || echo some spaces