Issue on read_file using a while loop in Bash/sh

Question

Does anyone know why after the first iteration I am out of the while loop here ? It used to work like yesterday!! (Same input file containing many lines, no new-lines)

#!/bin/sh
FLAGS_IN=MY_TEXT_FILE_CONTAINING_LOTS_OF_LINE

while read  BENCHMARK DATASET  CF
do
    echo "$BENCHMARK"
    echo "$DATASET"
    echo "$CF"
    N=$((N + 1))    

cd $tmp    
echo "**********************************************************"
            GCC_OPT="-O3"
            OPT_FLAGS=$CF
###### do sth



tmp=$PWD
done <  $FLAGS_IN

exit 0

debugging, I am sure the scripts work till the end of the loop pretty fine.

Answer 1

Your #do sth apparently contains a command that reads from standard input, so the next time the read executes, the end of the stream is reached. Pick a file handle you aren't using (3 is probably safe), and use that for your while loop:

while read BENCHMARK DATASET CF <&3
do
    # ...
done 3< $FLAGS_IN