Length of string in bash

How do you get the length of a string stored in a variable and assign that to another variable?

myvar="some string"
echo ${#myvar}  
# 11

How do you set another variable to the output 11?

To get the length of a string stored in a variable, say:

myvar="some string"
size=${#myvar} 

To confirm it was properly saved, echo it:

$ echo "$size"
11

UTF-8 string length

In addition to fedorqui's correct answer, I would like to show the difference between string length and byte length:

myvar='Généralités'
chrlen=${#myvar}
oLang=$LANG oLcAll=$LC_ALL
LANG=C LC_ALL=C
bytlen=${#myvar}
LANG=$oLang LC_ALL=$oLcAll
printf "%s is %d char len, but %d bytes len.\n" "${myvar}" $chrlen $bytlen

will render:

Généralités is 11 char len, but 14 bytes len.

you could even have a look at stored chars:

myvar='Généralités'
chrlen=${#myvar}
oLang=$LANG oLcAll=$LC_ALL
LANG=C LC_ALL=C
bytlen=${#myvar}
printf -v myreal "%q" "$myvar"
LANG=$oLang LC_ALL=$oLcAll
printf "%s has %d chars, %d bytes: (%s).\n" "${myvar}" $chrlen $bytlen "$myreal"

will answer:

Généralités has 11 chars, 14 bytes: ($'G\303\251n\303\251ralit\303\251s').

Nota: According to Isabell Cowan's comment, I've added setting to $LC_ALL along with $LANG.

Length of an argument, working sample

Argument work same as regular variables

showStrLen() {
    local bytlen sreal oLang=$LANG oLcAll=$LC_ALL
    LANG=C LC_ALL=C
    bytlen=${#1}
    printf -v sreal %q "$1"
    LANG=$oLang LC_ALL=$oLcAll
    printf "String '%s' is %d bytes, but %d chars len: %s.\n" "$1" $bytlen ${#1} "$sreal"
}

will work as

showStrLen théorème
String 'théorème' is 10 bytes, but 8 chars len: $'th\303\251or\303\250me'

Useful printf correction tool:

If you:

for string in Généralités Language Théorème Février  "Left: ←" "Yin Yang ☯";do
    printf " - %-14s is %2d char length\n" "'$string'"  ${#string}
done

 - 'Généralités' is 11 char length
 - 'Language'     is  8 char length
 - 'Théorème'   is  8 char length
 - 'Février'     is  7 char length
 - 'Left: ←'    is  7 char length
 - 'Yin Yang ☯' is 10 char length

Not really pretty output!

For this, here is a little function:

strU8DiffLen() {
    local charlen=${#1} LANG=C LC_ALL=C
    return $(( ${#1} - charlen ))
}

or written in one line:

strU8DiffLen() { local chLen=${#1} LANG=C LC_ALL=C;return $((${#1}-chLen));}

Then now:

for string in Généralités Language Théorème Février  "Left: ←" "Yin Yang ☯";do
    strU8DiffLen "$string"
    printf " - %-$((14+$?))s is %2d chars length, but uses %2d bytes\n" \
        "'$string'" ${#string} $((${#string}+$?))
  done 

 - 'Généralités'  is 11 chars length, but uses 14 bytes
 - 'Language'     is  8 chars length, but uses  8 bytes
 - 'Théorème'     is  8 chars length, but uses 10 bytes
 - 'Février'      is  7 chars length, but uses  8 bytes
 - 'Left: ←'      is  7 chars length, but uses  9 bytes
 - 'Yin Yang ☯'   is 10 chars length, but uses 12 bytes

Unfortunely, this is not perfect!

But there left some strange UTF-8 behaviour, like double-spaced chars, zero spaced chars, reverse deplacement and other that could not be as simple...

Have a look at diffU8test.sh or diffU8test.sh.txt for more limitations.

I wanted the simplest case, finally this is a result:

echo -n 'Tell me the length of this sentence.' | wc -m;
36

You can use:

MYSTRING="abc123"
MYLENGTH=$(printf "%s" "$MYSTRING" | wc -c)

• wc -c or wc --bytes for byte counts = Unicode characters are counted with 2, 3 or more bytes.
• wc -m or wc --chars for character counts = Unicode characters are counted single until they use more bytes.

In response to the post starting:

If you want to use this with command line or function arguments...

with the code:

size=${#1}

There might be the case where you just want to check for a zero length argument and have no need to store a variable. I believe you can use this sort of syntax:

if [ -z "$1" ]; then
    #zero length argument 
else
    #non-zero length
fi

See GNU and wooledge for a more complete list of Bash conditional expressions.