"How to read lines from a file"

sharath.bv · 02-01-2008, 01:39 AM

Hi,

I want to read lines from a file line-by-line and to display those lines on the terminal.
Can any one please provide a shell script for this.

lazlow · 02-01-2008, 01:49 AM

cat filename | more -1
The "|" is the pipe sysmbol (shift \ on my keyboard).

eoo · 02-01-2008, 01:55 AM

Hi,

I'm not sure what you're trying to do, but I'd use sed, e.g.

Quote:

sed -n "${i}p" $file

A longer longer example would be something like

Quote:

#! /bin/bash

file=/etc/fstab
nlines=$(wc -l $file | cut -f1 -d' ')
i=0

while [ $i -le $nlines ]
do
echo "Give me a line number"
read i
sed -n "${i}p" $file
done

echo "Reached end"

Hope this helps

Cheers

Disillusionist · 02-01-2008, 02:34 AM

Quote:

Originally Posted by sharath.bv

Hi,

I want to read lines from a file line-by-line and to display those lines on the terminal.
Can any one please provide a shell script for this.

This is obviously just a starting point, so please forgive me for asking.

What are you trying to achieve?

To read each line into a variable you could do:

Code:

#!/bin/bash
cat myfile|while read line
do
   ##perform some checks
   echo $line
done

However, this strips out any leading spaces or tab characters, therefore you may not get what you are after.

To do the same thing in Perl (which doesn't strip out leading spaces or tab characters):

Code:

#!/usr/bin/perl
open(INPUT, "myfile") or die "Could not open input file";

while (<INPUT>) {
   ##perform some checks
   print;
}

close(INPUT);

sharath.bv · 02-01-2008, 03:41 AM

Thanks all,
i got the answer.........

H_TeXMeX_H · 02-01-2008, 07:47 AM

The simplest and most readable way is (IMO):

Code:

while read line
do
  echo $line
done < file