How to read one line of a file each time ENTER key is pressed in Linux?-CodePudding

I am trying to come up with a script that will let the user read one line of the text file on each input of enter key until the file is done. What i tried so far:

while read -r line
 do read input
   if [[ -z $input ]]; then
     echo $line
 done < file.txt

while read -r line
echo | echo $line
done < file.txt

with the error:

sh: -c: line 3: syntax error near unexpected token `done'
sh: -c: line 3: `done < file.txt'

update: i forgot "fi" at the end of "if". however,

while IFS= read -r line
do
    read input
    if [[ -z $input ]]
    then
        echo $line
    fi
done < filename.txt

This time i am not getting any error, but it does not expect my enter input and does not print anything.

CodePudding user response：

Update: solved by replacing

read input

with

read input </dev/tty

CodePudding user response：

read reads from standard input by default. Your standard input is set to a file (< filename.txt). bash however lets you specify the fd to read from:

$ cat test
line 1
line 2
line 3

You received only some lines from filename.txt while others are consumed by read -r line:

$ while IFS= read line; do
    read line
    echo $line
  done < test
line 2

Here's how to use a different fd:

$ while IFS= read -u4 line; do
    read -s
    echo $line
  done 4< test
line 1
line 2
line 3

See man page of bash (or whatever shell you are using) for the read command.