bash while read loop arguments from variable issue

Question

I have a bash script with following variable:

operators_list=$'andrii,bogdan,eios,fre,kuz,pvm,sebastian,tester,tester2,vincent,ykosogon'

while IFS=, read -r tech_login; do


    echo "... $tech_login ..."

done <<< "$operators_list"

I need to read arguments from variable and work with them in loop. But it returns echo only one time with all items:

+ IFS=,
+ read -r tech_login
+ echo '... andrii,bogdan,eios,fre,kuz,pvm,sebastian,tester,tester2,vincent,ykosogon ...'
... andrii,bogdan,eios,fre,kuz,pvm,sebastian,tester,tester2,vincent,ykosogon ...
+ IFS=,
+ read -r tech_login

What am I doing wrong? How to rework script, so it will work only with one item per time?

KamilCuk · Accepted Answer · 2018-10-18 09:24:46Z

1

operators_list=$'andrii,bogdan,eios,fre,kuz,pvm,sebastian,tester,tester2,vincent,ykosogon'

So you have strings separated by ,. You can do that multiple ways:

using bash arrays:

IFS=, read -a operators <<<$operators_list
for op in "${operators[@]}"; do
    echo "$op"
done

Using a while loop, like you wanted:

while IFS= read -d, -r op; do
    echo "$op"
done <<<$operators_list

Using xargs, because why not:

<<<$operators_list xargs -d, -n1 echo

The thing with IFS and read delimeter is: read reads until delimeter specified with -d. Then after read has read a full string (usually whole line, as default delimeter is newline), then the string is splitted into parts using IFS as delimeter. So you can:

while IFS=: read -d, -r op1 op2; do
    echo "$op1" "$op2"
done <<<"op11:op12,op12:op22"

answered Oct 18, 2018 at 9:24

KamilCuk

146k8 gold badges84 silver badges154 bronze badges

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

2 Comments

Vasyl Stepulo Over a year ago

Thanks! Forgot about -d, as delimiter!

Nahuel Fouilleul Over a year ago

note that the read exit status for last element is not 0, but could be handled : while IFS= read -d, -r op; [[ $op ]]; do ... but this would stop on first empty element otherwise while IFS= read -d, -r op || [[ $op ]]; do ..., howvwer for the last item would contain the final \n due to here string

Collectives™ on Stack Overflow

bash while read loop arguments from variable issue

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related