Calling ssh in a loop is destroying the loop variable context (ksh93 on AIX 7.1) - ksh

Question

I'm posting this in case anyone else runs into this issue. I will open a case with IBM, and I'll report back if there's an update from them.
I was having a problem on AIX 7.1 (but not on 6.1) when I'm using a file
to drive a loop (eg: cat myfile.txt | while read myvar). Calling ssh
from within the loop causes the loop to exit prematurely on the first iteration.
In my real-life example I wasn't using "ls" to populate the file, but doing so here made it easier to demonstrate.
I've got the following code:
#!/usr/bin/ksh93
ssh LESAUN01 -l root "ls -1 c*" > file.list
echo "------------------------------------------"
cat file.list
echo "------------------------------------------"
echo ""
echo "Loop 1"
echo ""
cat file.list | while read file1
do
echo " File: $file1"
done
echo ""
echo "Loop 2"
echo ""
cat file.list | while read file2
do
echo " File: $file2"
ssh LESAUN01 -l root "ls -l $file2"
done
echo ""
echo "Done"
exit
When I run it from an AIX 6.1 lpar I get these expected results
-----------------------------------------
client.txt
customer_handover.log
------------------------------------------
Loop 1
File: client.txt
File: customer_handover.log
Loop 2
File: client.txt
-rw-r--r-- 1 root root 91323 Feb 12 2015 client.txt
File: customer_handover.log
-rw------- 1 root root 27533 Aug 31 18:04 customer_handover.log
Done
When run on 7.1 I get this result:
------------------------------------------
client.txt
customer_handover.log
------------------------------------------
Loop 1
File: client.txt
File: customer_handover.log
Loop 2
File: client.txt
-rw-r--r-- 1 root root 91323 Feb 12 2015 client.txt
Done
My solution was to feed the loop from an array instead of a file (after loading the file into the array) which works as expected.
This works on both 6.1 and 7.1
#!/usr/bin/ksh93
ssh LESAUN01 -l root "ls -1 c*" > file.list
echo "------------------------------------------"
cat file.list
echo "------------------------------------------"
echo ""
echo "Loop"
echo ""
i=0
set -A file_array
cat file.list | while read line
do
file_array[ $i ]="$line"
(( i++ ))
done
for x in "${!file_array[#]}"
do
echo " File: ${file_array[$x]}"
ssh LESAUN01 -l root "ls -l ${file_array[$x]}"
done
echo ""
echo "Done"
exit
Which gives this expected result.
------------------------------------------
client.txt
customer_handover.log
------------------------------------------
Loop
File: client.txt
-rw-r--r-- 1 root root 91323 Feb 12 2015 client.txt
File: customer_handover.log
-rw------- 1 root root 27533 Aug 31 18:04 customer_handover.log
Done

Answer 1

cat file.list | while read file2
do
echo " File: $file2"
ssh LESAUN01 -l root "ls -l $file2"
done
The output of cat file.list is the standard input for every command inside the loop. ssh reads from its standard input in order to relay the stream to the remote process, so it's consuming the cat output.
A simple fix is to redirect ssh's standard input:
cat file.list | while read file2
do
echo " File: $file2"
ssh LESAUN01 -l root "ls -l $file2" < /dev/null
done