CODEWITHSUNDEEP
arraysbasharguments
girdeux
girdeux

Reputation: 720

Length of array passed as an argument to a function

I need to pass an array as an argument to a function (that is fine) and then get its length (I don't get that to work).

Working example:

function foo {
 declare -a idn=("${!1}")
 echo "idn=${idn[@]}"
 n=${#idn[@]}
 echo "n=$n"
}

identifier=(a b c d e)
echo "len is ${#identifier[*]}"
echo foo
foo identifier[*]

The output of that is:

len is 5              #that is OK
foo
idn=a b c d e
n=1                   #should be 5

Length outside function is ok, but it is not inside the function.

I am using GNU bash, version 4.3.42(1)-release (x86_64-suse-linux-gnu)

Upvotes: 1

Views: 114

Answers (3)

Philippe
Philippe

Reputation: 26592

Your original script should work by just changing last line to :

foo "identifier[@]"

Upvotes: 2

Freddy
Freddy

Reputation: 4688

If you want to pass the individual arguments of the array a, b, c, d, e to your function, use foo "${identifier[@]}". Then in the function you can use $# to get the number of arguments.

Or if you want to pass the name of the variable to your function, you could use a local nameref variable idn which is a reference to the identifier array.

foo() {
  echo "n=$#"
}

foo2() {
  local -n idn=$1
  echo "n=${#idn[@]}"
}

identifier=(a b c d e)
echo "len is ${#identifier[*]}"
foo "${identifier[@]}"
foo2 identifier

Output:

len is 5
n=5
n=5

Upvotes: 0

Léa Gris
Léa Gris

Reputation: 19555

Either use a -nameref variable like this:

#!/usr/bin/env bash

foo ()
{
  # If argument 1 is not an array, return an error
  [ "${!1@a}" = 'a' ] || return 2

  # Make idn a nameref variable referrencing the array name from argument 1
  declare -n idn="$1"

  echo 'idn:' "${idn[@]}"
  n=${#idn[@]}
  echo 'n:' "$n"
}

identifier=(a b c d e)
echo "len is ${#identifier[*]}"
echo foo
foo identifier

Or pass array elements as value:

#!/usr/bin/env bash

foo ()
{
   declare -a idn=("${@}")

   echo 'idn:' "${idn[@]}"
   n=${#idn[@]}
   echo 'n:' "$n"
}

identifier=(a b c d e)
echo "len is ${#identifier[*]}"
echo foo
foo "${identifier[@]}"

Upvotes: 2

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