I am making a bash script and I have encountered a problem. So let's say I got this
function create_some_array(){
for i in 0 1 2 3 .. 10
do
a[i]=$i
done
}
create_some_array
echo ${a[*]}
Is there any way I can make this work? I have searched quite a lot and nothing I found worked.
I think making the a[] a global variable should work but I can't find something that actually works in my code. Is there any way to return the array from the function to main program?
Thanks in advance
This won't work as expected when there are whitespaces in the arrays:
function create_some_array() {
local -a a=()
for i in $(seq $1 $2); do
a[i]="$i $[$i*$i]"
done
echo ${a[@]}
}
and worse: if you try to get array indices from the outside "a", it turns out to be a scalar:
echo ${!a[@]}
even assignment as an array wont help, as possible quoting is naturally removed by the echo line and evaluation order cannot be manipulated to escape quoting: try
function create_some_array() {
...
echo "${a[@]}"
}
a=($(create_some_array 0 10))
echo ${!a[@]}
Still, printf seems not to help either:
function create_some_array() {
...
printf " \"%s\"" "${a[@]}"
}
seems to produce correct output on one hand:
$ create_some_array 0 3; echo
"0 0" "1 1" "2 4" "3 9"
but assignment doesn't work on the other:
$ b=($(create_some_array 0 3))
$ echo ${!b[@]}
0 1 2 3 4 5 6 7
So my last trick was to do assignment as follows:
$ eval b=("$(create_some_array 0 3)")
$ echo -e "${!b[@]}\n${b[3]}"
0 1 2 3
3 9
Tataaa!
P.S.: printf "%q " "${a[@]}" also works fine...
This works fine as described. The most likely reason it doesn't work in your actual code is because you happen to run it in a subshell:
cat textfile | create_some_array
echo ${a[*]}
would not work, because each element in a pipeline runs in a subshell, and
myvalue=$(create_some_array)
echo ${a[*]}
would not work, since command expansion happens in a subshell.
ls -i "$i" | awk '{print $1}'; inode[count]=$j; This is the part i insert into an array. And when I try to echo this outside the function it dosnt work –
Orthicon You can make an array local to a function, and then return it:
function create_some_array(){
local -a a=()
for i in $(seq $1 $2); do
a[i]=$i
done
echo ${a[@]}
}
declare -a a=()
a=$(create_some_array 0 10)
for i in ${a[@]}; do
echo "i = " $i
done
Hi here is my solution:
show(){
local array=()
array+=("hi")
array+=("everything")
array+=("well?")
echo "${array[@]}"
}
for e in $(show);do
echo $e
done
Try this code on: https://www.tutorialspoint.com/execute_bash_online.php
Both these work for me with sh and bash:
arr1=("192.168.3.4" "192.168.3.4" "192.168.3.3")
strArr=$(removeDupes arr1) # strArr is a string
for item in $strArr; do arr2+=("$item"); done # convert it to an array
len2=${#arr2[@]} # get array length
echo "${len2}" # echo length
eval arr3=("$(removeDupes arr1)") # shellcheck does not like this line and won't suppress it but it works
len3=${#arr3[@]} # get array length
echo "${len3}" # echo length
As an aside, the removeDupes function looks like this:
removeDupes() {
arg="$1[@]"
arr=("${!arg}")
len=${#arr[@]}
resultArr=()
# some array manipulation here
echo "${resultArr[@]}"
}
This answer is based on but better explains and simplifies the answers from @Hans and @didierc
Your function doesn't return an array. It creates a global array variable called $a.
function create_some_array(){ for i in 0 1 2 3 .. 10 do a[i]=$i done }
To return an array:
function create_some_array(){
local a
for i in 0 1 2 3 .. 10; do
a[i]=$i
done
printf "%s\n" "${a[@]}"
}
# capture the created array:
readarray -t my_array < <(create_some_array)
# print its elements
for element in "${my_array[@]}"; do
echo " - ${element}"
done
This method, doesn't just simulate a returned array, but it also respects the spaces in a particular element.
Hope it helps
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bash -x script_namewhich will trace what is happening. – Tintorettomkdir tmp; touch tmp/{file1,file2}; ln tmp/file2 tmp/file3; bash yourscript tmpoutputs "The index number of .../tmp/file2 is 28578767 and its hard link is 2", "file2 is hardlinked to file3 with indexnumber: 28578767, file3 is hardlinked to file2 with indexnumber: 28578767". Seems to be working fine. – Groundnut