bash: Passing arrays with spaces

jakeo25 · 01-04-2008, 01:17 PM

All,

I am in a bit of a pickle over this one. I have arrays of strings I need to pass to a function. The problem is that when an array element has a space, this is now treated as a new array element, due to the echo-ing process, parameter-passing paradigm.

Here is sample:

-----------------------------------------------------------
#!/bin/bash
myarray=( "one 1" "two2" "three 3")

function myArrayFunction ()
{
LIST=( `echo "$1"` )
echo "Array size is ${#LIST[*]}"
for A in $(seq 0 $((${#LIST[*]} - 1))); do
echo "${LIST[$A]}"
done
}

echo "Initial array size is ${#myarray[*]}"

argument=`echo ${myarray[*]}`
myArrayFunction "$argument"
------------------------------------------------------------

output of this is

Initial array size is 3
Array size is 5
one
1
two2
three
3

Perhaps I have missed some trick that could help?

Jake

jozyba · 01-04-2008, 03:13 PM

You've emptied out the contents of an array with 3 elements into a string called 'argument'. Then, using the white space, you've split the string up into 5 separate "words" and asigned them one by one to the array called 'LIST'.

It would be simpler if you avoided all that unnecessary juggling from one variable to another:

Code:

#!/bin/bash

myarray=( "one 1" "two2" "three 3")

function myArrayFunction () {
    echo "Array size is ${#myarray[*]}"
    for A in $(seq 0 $((${#myarray[*]} - 1))); do
        echo "${myarray[$A]}"
    done
}

echo "Initial array size is ${#myarray[*]}"

myArrayFunction

jakeo25 · 01-04-2008, 03:26 PM

Perhaps I was not clear with my post, as your solution suggests.

In order to pass an array to a function, use the lines

argument=echo "${array[@}}"
MyArrayFunction $argument

Yes, I understand what this is doing. What I am asking is that I will be passing several arrays to MyArrayFunction, each with different sizes and one or more spaces in the elements.

I could explicitly type in the array as you suggest, but as a C programmer, I like to avoid repeating code and potential typing mistakes in a large script.

jakeo25

radoulov · 01-04-2008, 04:36 PM

Something ugly like this:

Code:

$ declare -f afnc
afnc ()
{
    local args=($(IFS='
';printf "%s\n" "$@"));
    printf "Array size is %d\n" ${#args[@]};
    for ((i=0; i<${#args[@]}; i++))
    do
        printf "%s\n" "${args[i]}";
    done
}

$ array=("o n e" two "thr ee" "fo ur")

$ afnc "${array[@]}"
Array size is 4
o n e
two
thr ee
fo ur

With zsh it would be easier.

jozyba · 01-04-2008, 05:45 PM

Code:

#!/bin/bash

myarray=( "one 1" "two2" "three 3" )

function myArrayFunction ()
{
    y=$#
    for (( x=0; x<y; x++ )); do
        LIST[x]="$1"
        shift
    done
    echo "Array size is ${#LIST[*]}"
    for (( A=0; A<${#LIST[*]}; A++ )); do
        echo "$A = ${LIST[$A]}"
    done
}

echo "Initial array size is ${#myarray[*]}"

argument=( "${myarray[@]}" )
myArrayFunction "${argument[@]}"

radoulov · 01-05-2008, 04:06 AM

Or (I definitely need more coffee

):

Code:

$ afnc (){
> printf "Array size is %d\n" "${#@}";
> printf "%s\n" "$@"
> }
$ array=("o n e" two "thr ee" "fo ur")
$ afnc  "${array[@]}"
Array size is 4
o n e
two
thr ee
fo ur

jakeo25 · 01-05-2008, 11:55 AM

Simple, elegant & clever. The only question is why I didn't think of that.

ty,

j

jakeo25 · 01-07-2008, 11:32 AM

Just an FYI to those who are reading this topic.

1) The lines

argument=( "${myarray[@]}" )
myArrayFunction "${argument[@]}"

could be combined:

myArrayFunction "${myarray[@]}"

2) It was interesting to observe the differences with dereference parameters '@' and '*', e.g.

myArrayFunction "${myarray[*]}" # ERROR: entire array as a single element

myArrayFunction "${myarray[@]}" # works!

The positional parameters' rules apply here, from the "Advanced BASH scripting Guide":

$* All of the positional parameters, seen as a single word

$@ Same as $*, but each parameter is a quoted string ... each parameter in the argument list is seen as a separate word.

rambutan · 06-05-2009, 08:00 AM

Here is a similar script I wrote to use ls to fill an array.

#!/bin/bash

IFS=$'\n'
### VERY IMPORTANT - changes break point for arrays!!! no break on spaces

ArrayFiles=(`ls /Data/Writer/Linux-Computers/ --format=single-column -p | grep -v /`)
# what's it do?
# ls --format=single-column ===> output is a single column, not folded multiple columns
# ls -p ===> output appends the "/" to the end of any directory names
# grep -v / ===> means select all EXCEPT lines with / --- this means ignore the directories

# echo the element count
element_count=${#ArrayFiles[*]}
echo "There are $element_count elements in the array"

# make a loop to show the records
i="0"
while [ $i -lt $element_count ]
do
echo $i \> ${ArrayFiles[$i]}
# step by 1
i=$[$i+1]
done