I have 2 strings:


I would like to know if there was some way to count the amount of letters in $answer that are same as $guess, in this case I should get number 7. Some notes are that $answer and $guess will change.'

Because of the accusation that I posted a duplicate, the one suggested is asking for length of word; I am asking for how many letters in 2 strings are equal. For example, "Stackoverflow" and "stkflw". would want something to count how many letters in "stkflw" are equal to the letters in "Stackoverflow". I need it to count all letters in a word, for an example, "Test" should return 4 because it has 4 letters (an answer has one that returns 3 with test which is not desirable)

If this could be done in bash, that would be great! :)

  • am sorry, I completely misread the question...
    – Sundeep
    Mar 4 '17 at 3:58
  • It's okay, i likely phrased it all backwards. :)
    – Lee Ikard
    Mar 4 '17 at 4:00
  • 1
    @LeeIkard can you add more examples, like for fete and feet, good and goodness, par and rap, etc
    – Sundeep
    Mar 4 '17 at 4:04
  • A bash version is preferred.
    – Lee Ikard
    Mar 5 '17 at 21:56
  • @Sundeep I didn't include a bunch of exmaples because they will always vary as a random word will be chosen as an answer (and the guess will always vary. That's the reason the code in the question is set as a variable, not string)
    – Lee Ikard
    Mar 5 '17 at 21:58

In Perl, the transliteration operator tr// (which works pretty much like the tr shell utility) will return the number of characters that were transliterated.

$ perl -e 'print("spgheti" =~ tr/spaghetti/spaghetti/, "\n")'

I.e. "seven characters in spgheti are found in spaghetti".

$ perl -e 'print("spaghetti" =~ tr/spgheti/spgheti/, "\n")'

I.e. "eight characters in spaghetti are found in spgheti" (since t occurs twice in spaghetti, it is counted twice).

Putting a loop around it:

while read word1 word2; do
  perl -e 'printf("%s / %s: %d\n", $ARGV[0], $ARGV[1],
    eval "$ARGV[0] =~ tr/$ARGV[1]/$ARGV[1]/")' "$word1" "$word2"
done <<LIST_END
stkflw Stackoverflow
fete feet
good goodness
par rap

The Perl eval() call in necessary to be able to insert $ARGV[1] into the search and replacement list of tr//.


stkflw / Stackoverflow: 5
fete / feet: 4
good / goodness: 4
par / rap: 3

Or, reading from a file with two words on each line:

while read word1 word2; do
  # as before
done <wordpairs
  • Works well, it counts all letters, and returns me the number. However, this is in perl, I would like it in bash. I will use this answer in my project until a bash version comes along (that counts all letters, even repeating ones)
    – Lee Ikard
    Mar 5 '17 at 21:55

Here's how to do it in bash.

# ----------------------------------------------------------------------------
# $1 answer (contains the "source" string)
# $2 guess (contains individual characters to be counted from $answer)
# prints to standard output a count of the characters from 'guess' which
# appear in 'answer'
# ----------------------------------------------------------------------------

# for each character in $guess, observe whether its elimination from
# $answer causes the resultant string to be different; if so, it exists,
# therefore increment a counter

# iterate over the characters of $guess
for (( i=0; i < ${#guess}; i=i+1 )); do

    # attempt to extract current character

    # has $answer changed?
    if [[ $answer_after_extract != $answer ]]; then
        count=$(( count + 1 ))

echo $count


$ ./answer spaghetti spgheti

$ ./answer abcdefghijklmnopqrstuvwxyz aeiou

$ ./answer abcdefghijklmnopqrstuvwxyz xyzzy
  • Tried with "test" and "test" and it gave me 3, i would like to have it return 4 since there are 2 T's in test (and other words might have repeating letters)
    – Lee Ikard
    Mar 5 '17 at 21:52
  • Ok, no problem. My original script counted only "distinct" (non-repeating) characters from the "guess". One simple change will count all characters, namely: replacing the two forward-slashes with a single forward slash on line 25: answer_after_extract=${answer/$current_char} Mar 7 '17 at 0:51

# find the individual letters in the answer
# use an associative array to manage duplicates
declare -A letters=()
for ((i=0; i < ${#answer}; i++)); do

# remove duplicate letters in the guess.
# could use the above technique, but here's another one
guess_uniq=$( sed 's/./&\n/g' <<< "$guess" | sort -u | tr -d '\n' )

# loop over the unique letters of the guess, 
# and count how many letters are in the answer
for ((i=0; i < ${#guess_uniq}; i++)); do
    [[ ${letters[${guess_uniq:i:1}]} = "1" ]] && (( matches++ ))

if (( matches == ${#guess_uniq} )); then echo "Correct"; fi
  • returns "Correct" on every guess.
    – Lee Ikard
    Mar 5 '17 at 21:53
  • if that is meant as a bug report, I need more info Mar 5 '17 at 22:15
  • I use any answer and any guess, and it returns "correct" every time.
    – Lee Ikard
    Mar 6 '17 at 3:03
  • I see that it says Correct for any guess that only contains letters from the answer, even if it does not contain all the letters in answer Mar 6 '17 at 3:10
  • Oh, nevermind, i was wrong. But this doesn't exactly answer my question because it returns correct instead of a number.
    – Lee Ikard
    Mar 6 '17 at 5:03

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