Shell Programming and Scripting

I'm working on a new exercise that calls for a script that will take in two arguments on the command line (representing the range of line numbers) and will subsequently print those lines from a a specified file. Command line would look like this: ./lines_script.bash 5 15 <file.txt. The script would then spit out lines 5-15 from the text file (including the line number). The only caveat - I'm not supposed to use sed, awk, grep, head or tail.

Here's what I have so far:

Code:

COUNT=($1-1)
while read -r line; do
COUNT=$(( $COUNT +1))
if [$COUNT >= $2]; then
echo $COUNT
fi
done

When I run this on the command line- ./lines_script.bash 5 15 <file.txt it spits this garbage back at me:

./lines_script.bash: line 11: [20: command not found
./lines_script.bash: line 11: [21: command not found
./lines_script.bash: line 11: [22: command not found
./lines_script.bash: line 11: [23: command not found
./lines_script.bash: line 11: [24: command not found
./lines_script.bash: line 11: [25: command not found
./lines_script.bash: line 11: [26: command not found
./lines_script.bash: line 11: [27: command not found
./lines_script.bash: line 11: [28: command not found
./lines_script.bash: line 11: [29: command not found
./lines_script.bash: line 11: [30: command not found

[ and ] must have a spaces before and after them

Chubler! Thank you, I got that patched up, though I'm still getting garbage back.

Code:

COUNT=($1-1)
while read -r line; do
COUNT=$(( $COUNT +1))
if [ $COUNT >= $2 ]
then
echo "$COUNT"
fi
done

Working fine for me - what garbage do you get? And what would you expect, respectively?

Try this code (note it needs to be "hardened", e.g. checking if $1 and $2 were supplied, is $1 less than $2, etc.):

Code:

#!/bin/bash

ARGSTART=$1
ARGSTOP=$2

COUNT=0

while IFS= read -r line; do
 COUNT=$((COUNT+1))

  if [ $COUNT -ge $ARGSTART ] && [ $COUNT -le $ARGSTOP ]; then
   echo "$COUNT: $line"
  fi

done

Demo:

Code:

$ man bash | head -15 >bash.txt
$ ./script.sh 5 12 <bash.txt
5: NAME
6:        bash - GNU Bourne-Again SHell
7: 
8: SYNOPSIS
9:        bash [options] [file]
10: 
11: COPYRIGHT
12:        Bash is Copyright (C) 1989-2011 by the Free Software Foundation, Inc.
$

---------- Post updated at 06:24 PM ---------- Previous update was at 06:18 PM ----------

Don't know what OP gets, but I got some unary operator expected

Thank you, Junior. I'm trying that out now. And yes - I'm getting unary operator expected errors with my script.

---------- Post updated at 11:33 AM ---------- Previous update was at 11:18 AM ----------

That seems to have done the trick, junior-helper! Thank you.

The one thing I don't understand - why did you use "while IFS= read -r line; do" instead of "while read -r line; do"? I'm trying to make sure I understand what I'm doing and why it works. Thanks!

The IFS= sets IFS empty for the following read command, so the read does no word splitting. This ensures that leading space characters are not suppressed.