Bash-parsing string into an array of floating point numbers

Question

I wish to create an array of floating point numbers (called b) in BASH, the contents of the array is given by parsing the following variable adse :

echo $adse
16.92 18.29 19.18 20.87 2.78 2.88 2.77 2.83 2.80 2.78 2.73 2.73 2.75 2.93 2.91 2.93 2.77 4.64 2.67 3.01 6.78

so that b[1]=16.92; b[2]=18.29.....

How can I achieve this?

Answer 1

With

b=($adse)

you get a bash array b . Individual arguments can be accessed with ${b[index]} . Indices are zero-based, so the first element is ${b[0]} .

Be aware that you will find it difficult to do anything with these values in bash, though. It might be a good idea to use a scripting language that has support for floating point calculations, such as Perl or Python.

For a more in-depth discussion of bash arrays, see this link .

Answer 2

The canonical solution is:

read -r -d '' -a b <<<"$adse"

Unlike solutions which rely on default word-splitting of an unquoted expansion of $adse , the read built-in will not produce unwanted expansions of glob characters.

If you want to split the variable on some character other than whitespace, you can set IFS locally for the read :

IFS=: read -r -d '' -a b <<<"$adse"

That will not split on newlines. If you wanted to split on colon or newline, you could use IFS=$':\\n' .

Both of the above will set b[0] to the first element, not b[1] . If you wanted to start at b[1] , you could prepend 0 or some such to the input to read , and then unset "b[0]" afterwards.

help read to get an explanation of the options. Briefly, -r avoids interpretation of backslash escape sequences; -d '' causes the read to terminate at the end of input instead of the end of a line, and -ab causes the result to be placed in the array b .

Answer 3

Try with:

b=($(echo $adse))

But it begins with index 0, like:

echo ${b[0]}

that yields:

16.92

Answer 4

Although there is an easy solution to achieve what you want, I believe the following is also useful if, say, you have a string whose delimiters are not whitespace:

b=()
adse="16.92 18.29 19.18 20.87 2.78 2.88 2.77 2.83 2.80 2.78 2.73 2.73 2.75 2.93 2.91 2.93 2.77 4.64 2.67 3.01 6.78"

b=(${adse// / })

For example, if you had a string like this:

adse="16.92:18.29...etc"

You would have to change b=(${adse// / }) to:

b=(${adse//:/ })

However, for your particular case, all that is needed to parse the string into an array is already stated by Birei below.