number of tokens in bash variable

Question

how can I know the number of tokens in a bash variable (whitespace-separated tokens) - or at least, wether it is one or there are more.

Answer 1

For a robust, portable sh solution, see @JoSo's functions using set -f.

(Simple bash-only solution for answering (only) the "Is there at least 1 whitespace?" question; note: will also match leading and trailing whitespace, unlike the awk solution below:

 [[ $v =~ [[:space:]] ]] && echo "\$v has at least 1 whitespace char."

)

Here's a robust awk-based bash solution (less efficient due to invocation of an external utility, but probably won't matter in many real-world scenarios):

# Functions - pass in a quoted variable reference as the only argument.
# Takes advantage of `awk` splitting each input line into individual tokens by
# whitespace; `NF` represents the number of tokens.
# `-v RS=$'\3'` ensures that even multiline input is treated as a single input 
# string.
countTokens() { awk -v RS=$'\3' '{print NF}' <<<"$1"; }
hasMultipleTokens() { awk -v RS=$'\3' '{if(NF>1) ec=0; else ec=1; exit ec}' <<<"$1"; }

# Example: Note the use of glob `*` to demonstrate that it is not 
# accidentally expanded.
v='I am *'

echo "\$v has $(countTokens "$v") token(s)."

if hasMultipleTokens "$v"; then
  echo "\$v has multiple tokens."
else
  echo "\$v has just 1 token."
fi

Answer 2

I can't understand why people are using those overcomplicated bashisms all the time. There's almost always a straight-forward, no-bashism solution.

howmany() { echo $#; }
myvar="I am your var"
howmany $myvar

This uses the tokenizer built-in to the shell, so there's no discrepancy.

Here's one related gotcha:

myvar='*'
echo $myvar
echo "$myvar"
set -f
echo $myvar
echo "$myvar"

Note that the solution from @guns using bash array has the same gotcha.

The following is a (supposedly) super-robust version to work around the gotcha:

howmany() ( set -f; set -- $1; echo $# )

If we want to avoid the subshell, things start to get ugly

howmany() {
    case $- in *f*) set -- $1;; *) set -f; set -- $1; set +f;; esac
    echo $#
}

These two must be used WITH quotes, e.g. howmany "one two three" returns 3

Answer 3

The $# expansion will tell you the number of elements in a variable / array. If you're working with a bash version greater than 2.05 or so you can:

VAR='some string with words'
VAR=( $VAR )
echo ${#VAR[@]}

This effectively splits the string into an array along whitespace (which is the default delimiter), and then counts the members of the array.

EDIT:

Of course, this recasts the variable as an array. If you don't want that, use a different variable name or recast the variable back into a string:

VAR="${VAR[*]}"

Answer 4

Simple method:

$ VAR="a b c d"
$ set $VAR
$ echo $#
4

Answer 5

To count:

sentence="This is a sentence, please count the words in me."
words="${sentence//[^\ ]} "
echo ${#words}

To check:

sentence1="Two words"
sentence2="One"
[[ "$sentence1" =~ [\ ] ]] && echo "sentence1 has more than one word"
[[ "$sentence2" =~ [\ ] ]] && echo "sentence2 has more than one word"

Answer 6

set VAR='hello world'
echo $VAR | wc -w

here is how you can check.

if [ `echo $VAR | wc -w` -gt 1 ] 
then
    echo "Hello"
fi