I am having a bash script which is something like following,
cat filename | while read line
do
read input;
echo $input;
done
but this is clearly not giving me the right output as when I do read in the while loop it tries to read from the file filename because of the possible I/O redirection.
Any other way of doing the same?
This question is related to
bash
You can redirect the regular stdin through unit 3 to keep the get it inside the pipeline:
{ cat notify-finished | while read line; do
read -u 3 input
echo "$input"
done; } 3<&0
BTW, if you really are using cat
this way, replace it with a redirect and things become even easier:
while read line; do
read -u 3 input
echo "$input"
done 3<&0 <notify-finished
Or, you can swap stdin and unit 3 in that version -- read the file with unit 3, and just leave stdin alone:
while read line <&3; do
# read & use stdin normally inside the loop
read input
echo "$input"
done 3<notify-finished
I have found this parameter -u with read.
"-u 1" means "read from stdin"
while read -r newline; do
((i++))
read -u 1 -p "Doing $i""th file, called $newline. Write your answer and press Enter!"
echo "Processing $newline with $REPLY" # united input from two different read commands.
done <<< $(ls)
Try to change the loop like this:
for line in $(cat filename); do
read input
echo $input;
done
Unit test:
for line in $(cat /etc/passwd); do
read input
echo $input;
echo "[$line]"
done
echo "Enter the Programs you want to run:"
> ${PROGRAM_LIST}
while read PROGRAM_ENTRY
do
if [ ! -s ${PROGRAM_ENTRY} ]
then
echo ${PROGRAM_ENTRY} >> ${PROGRAM_LIST}
else
break
fi
done
It looks like you read twice, the read inside the while loop is not needed. Also, you don't need to invoke the cat command:
while read input
do
echo $input
done < filename
Source: Stackoverflow.com