Bash: Read lines from variable . Nested loop

Question

I am able to read line by line in the first loop, but 2nd loop returns all lines at once.
I want the second loop to read line-by-line similsr to the outer loop. How can I resolve this?

firstlist=`<some command that returns multi-line o/p>`
if [ "x$firstlist" != "x" ] ; then
    printf %s "$firstlist" |while IFS= read -r i
    do
        secondlist=`<some command that returns multi-line o/p>`
        if [ "x$secondlist" != "x" ] ; then
            printf %s "$secondlist" |while IFS= read -r j
            do
                doverify $i $j
            done
        else
            echo "Some message"
        fi
     done
else
    echo "some other message"
fi

Hi @Rajshekar Iyer, with your code for every i you get all the j. What exactly are you trying to achieve? — Dimitre Radoulov
– Dimitre Radoulov, Commented Oct 20, 2011 at 11:09
Hi @DimitreRadoulov, I want the second loop to read one line at a time too instead of the complete variable. — Rajshekar Iyer
– Rajshekar Iyer, Commented Oct 20, 2011 at 11:20
For me your code does exactly this, perhaps you should check the secondlist content? — Dimitre Radoulov
– Dimitre Radoulov, Commented Oct 20, 2011 at 11:28

Vlad · Accepted Answer · 2011-10-20 11:19:38Z

1

You should use -a instead of -r.

Example:

{0,244}$> echo "a b c" | { read -a j; echo ${j[0]}; echo ${j[1]}; echo ${j[2]}; }
a
b
c

edited Oct 20, 2011 at 11:19

answered Oct 20, 2011 at 11:12

Vlad

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Comments

Rajshekar Iyer · Accepted Answer · 2011-10-21 11:55:20Z

0

This worked for me as follows

firstlist=`<some command that returns multi-line o/p>`
  if [ "x$firstlist" != "x" ] ; then
  while IFS= read -r i
  do
    secondlist=`<some command that returns multi-line o/p>`
    if [ "x$secondlist" != "x" ] ; then
        while IFS= read -r j
        do
            doverify $i $j
        done <<< "$secondlist"
    else
        echo "Some message"
    fi
   done <<< "$firstlist"
else
  echo "some other message"
fi

Reference: http://mywiki.wooledge.org/BashFAQ/001 The <<< construct is called "here string" per the link

answered Oct 21, 2011 at 11:55

Rajshekar Iyer

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