How to count number of words from String using shell
BashBash Problem Overview
I want to count number of words from a String using Shell.
Suppose the String is:
input="Count from this String"
Here the delimiter is space ' ' and expected output is 4.
There can also be trailing space characters in the input string like "Count from this String ".
If there are trailing space in the String, it should produce the same output, that is 4. How can I do this?
Bash Solutions
Solution 1 - Bash
echo "$input" | wc -w
Use wc -w to count the number of words.
Or as per dogbane's suggestion, the echo can be got rid of as well:
wc -w <<< "$input"
If <<< is not supported by your shell you can try this variant:
wc -w << END_OF_INPUT
$input
END_OF_INPUT
Solution 2 - Bash
You don't need an external command like wc because you can do it in pure bash which is more efficient.
Convert the string into an array and then count the elements in the array:
$ input="Count from this String "
$ words=( $input )
$ echo ${#words[@]}
4
Alternatively, use set to set positional parameters and then count them:
$ input="Count from this String "
$ set -- $input
$ echo $#
4
Solution 3 - Bash
To do it in pure bash avoiding side-effects, do it in a sub-shell:
$ input="Count from this string "
$ echo $(IFS=' '; set -f -- $input; echo $#)
4
It works with other separators as well:
$ input="dog,cat,snake,billy goat,horse"
$ echo $(IFS=,; set -f -- $input; echo $#)
5
$ echo $(IFS=' '; set -f -- $input; echo $#)
2
Note the use of "set -f" which disables bash filename expansion in the subshell, so if the caller wants expansion it should be done beforehand (Hat Tip @mkelement0).
Solution 4 - Bash
Try the following one-liner:
echo $(c() { echo $#; }; c $input)
It basically defines c() function and passes $input as the argument, then $# returns number of elements in the argument separated by whitespace. To change the delimiter, you may change IFS (a special variable).
Solution 5 - Bash
echo "$input" | awk '{print NF}'
Solution 6 - Bash
I'll just chime in with a perl one-liner (avoiding 'useless use of echo'):
perl -lane 'print scalar(@F)' <<< $input
Solution 7 - Bash
It is efficient external command free way, like @dogbane's. But it works correctly with stars.
$ input="Count from *"
$ IFS=" " read -r -a words <<< "${input}"
$ echo ${#words[@]}
3
If input="Count from *" then words=( $input ) will invoke glob expansion. So size of words array will vary depending on count of files in current directory. So we use IFS=" " read -r -a words <<< "${input}" instead it.
Solution 8 - Bash
function count_item() {
return $#
}
input="one two three"
count_item $input
n=$?
echo $n
NOTE: function parameter passing treat space as separated argument, therefore $# works. $? is the return value of the recently called function.