How can I append an entry to an array in a while loop in bash?

Question

When I declare an array in bash $ ARRAY=('ele1' ele2') I can append an element to it with $ ARRAY+=('ele3').

echo ${ARRAY[@]}
ele1 ele2 ele3

However, inside a script in a while loop I don't get it to work:

FOUNDFILES=$(ls -lA)
LINE_CNT=1
ARRAY=()

echo -e "$FOUNDFILES" | while read line
        do
                ARRAY+=("test")
                LINE_CNT=$((LINE_CNT+1))
        done

echo "${ARRAY[@]}"
echo $LINE_CNT

LINE_CNT variable delivers the amount of files that were found, but my array stays empty. What am I doing wrong?

You are printing echo "${FILE_ARRAY[@]}" instead of echo "${ARRAY[@]}", maybe that lead you to believe that ARRAY is empty. — Socowi
– Socowi, Commented Dec 11, 2019 at 15:52
Right hand side of a pipe runs in a subshell. Use while ... done < <(echo -e "$FOUNDFILES") isntead. — choroba
– choroba, Commented Dec 11, 2019 at 15:52
Also, capturing a list of files in a plain variable and echo -e are both unsafe ways to handle the file list. See my answer here for a safe way to do it. — Gordon Davisson
– Gordon Davisson, Commented Dec 11, 2019 at 15:57
@Socowi That was a copy,paste mistake, edited it. Have confusing file names in my real example. — h0ch5tr4355
– h0ch5tr4355, Commented Dec 11, 2019 at 16:12
@choroba This somehow creates an endless loop in my case, but I think this is the right track. while ... \ndo \ndoSomething \ndone < <(echo -e "$FOUNDFILES") — h0ch5tr4355
– h0ch5tr4355, Commented Dec 11, 2019 at 16:18

chepner · Accepted Answer · 2019-12-11 16:27:27Z

5

A few things:

Don't assume that find outputs exactly one file name per line; that breaks in the presence of filenames containing newlines.
Don't assume that newlines output by find are the only whitespace in the output.
Don't use find at all when a glob will do.

shopt -s globstar
foundfiles=(./**/"$1")

declare -a array
line_cnt=1
for f in "${foundfiles[@]}"; do
    array+=(test)
    line_count=$((line_count + 1))
done

If your call to find is more complex than a glob can handle, and your version of find can output null-delimited file names, use

# -d for readarray was introduced in bash 4.4; earlier versions
# require something more complex; see Gordan Davidson's answer at
# https://stackoverflow.com/a/1120952/1126841
readarray -t -d $'\0' < <(find . ... -name "$1" -print0)

If your find does not support outputting null-delimited file names, rethink writing this in bash. (You might consider using zsh, which has a vastly richer set of glob features that can eliminate many cases where you would otherwise need find.)

edited Dec 11, 2019 at 16:27

answered Dec 11, 2019 at 15:58

chepner

538k77 gold badges594 silver badges746 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

h0ch5tr4355 Over a year ago

How to use this? ARRAY=(./**/"$1") didnt create an array

h0ch5tr4355 Over a year ago

Furthermore there are no newlines in file names in my case.

h0ch5tr4355 Over a year ago

Ok now I managed it to work. This is indeed very helpful. However this rather advises not to use find, not answering my question of what I was doing wrong namely not considering the creation of a subshell. FOUNDFILES=$(find . -name "$1") was just a placeholder, because I have this while loop in many scripts and I wondered why I could increment the counter but not modify the array.

Paul Hodges Over a year ago

Don't forget shopt -s globstar; - c.f. bash's manual

chepner Over a year ago

I find the assertion that one variable updates but the other does not dubious.

|

Collectives™ on Stack Overflow

How can I append an entry to an array in a while loop in bash?

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related