Shell Programming and Scripting

Hi All,

I am facing a problem while taking input from user in Shell Script. Basically , I want to read a file line by line. And I want to remove certain lines of that file.But before removing those lines , I need to ask the user whether user wants to remove the lines. If user inputs "Yes" , the Shell Script will remove the line.

But the Shell Script that I have written is not stopping it's execution to take input from user.

e.g.

If a file abc.txt has following content :

Code:

1
2
3
4
5
6
7

then I want to remove the line with content as 3.
The Shell Script , I am using is :

Code:

while read fileContent
do
	if test "$fileContent" -eq "3"
	then
		echo " Do you want to remove this line ? (Y/N ) : "
	
		read inputline
		
		if test "$inputline" = "Y"
		then
			[Code to remove line from file ....]
		fi
		echo $what
	fi
done < abc.txt

The Shell Script execution is not allowing user to enter input , instead it's displaying content of line 4 and terminating.

Can anyone please solve above issue ?

TIA

The problem is that when you redirect standard input for the while loop with "done < abc.txt", that redirection is in effect for all the commands executed within it. The internal read statement's stdin is not reading from the terminal, it too redirected to read from abc.txt.

A couple of solutions:

1. You can save the original source of stdin for use by the internal read statement so that it can read from the terminal:

while read fileContent
....
read -u3 inputline
....
done 3<&0 < abc.txt

2. Use a different descriptor (instead of stdin) for reading the file.

exec 3<abc.txt
while read -u3 fileContent
...
read inputline
...
done

Regards,
alister

Or you can use:

Code:

read inputline < /dev/tty

Thanks Scrutinizer and alister. Quite helpful replies