While loop read line not working

Shell Programming and Scripting
1

Hi,
I am trying to read a file line by line inside of a while loop. This while loop is part of a here document.

while read  line
do
  ssh -t $2@$remotehost  <<REMOTE

   ls path/to/dir > $path_to_dir

    while read line1
        do
                echo "LINE --- $line"
        done <$path_to_dir

REMOTE
done < "$filename"

The problem here is.
$path_to_dir has 3 lines.
echo "LINE ----" is printed 3 times however the $line variable does not print.

2

<$path_to_dir tries to read from that as if it's a filename -- not as if it's a list of lines. Technically it's valid for a filename to have newlines in it, strangley enough! The only invalid characters for a filename are NULLs and forward slashes.

Depending on what shell you're using you could do:

while read line1
do
done <<<"${list_of_lines}"

Also, you should always, always quote your variables unless you want them to start splitting when they end up with spaces in them. No reason not to.

3

That doesn't work. Now instead of printing the LINE --- 3 times , it prints LINE --- just once.

Also, I am not very clear what you meant by it trying to read line from filename.

I have a surrounding while loop to that above code and that works perfectly file

while read remotehost
do
 Above mentioned Code
done < "$remotehostlist"

This while loop works fine and provides me the value of remote host.
However the inner while loop does not print the value of $line.

That is the weird part

---------- Post updated at 02:41 PM ---------- Previous update was at 02:27 PM ----------

I changed the code to try this as well.. It still doesnt work!!

while read  remotehost
do
  ssh -t $2@$remotehost  <<REMOTE

   ls /path/to/dir | while read line
     do
        echo "LINE --- $line"
     done

REMOTE
done < "$remotehostlist"

This code still prints LINE --- 3 times. But does not print value of $line

4

Suddenly it's staring me in the face.

Even in a here-document, $line gets evaluated before the program is run, while it's still blank, so it becomes "LINE ---" before it even gets transmitted over ssh. Try escaping it like \$line.

1 Like
5

Thank you very much! That worked :slight_smile: