Shell script that accepts a filename and starting/ending line numbers as arguments, and displays all the lines between the given line numbers.
What does $# mean in Unix?
$# is the number of arguments, but remember it will be different in a function. $# is the number of positional parameters passed to the script, shell, or shell function. This is because, while a shell function is running, the positional parameters are temporarily replaced with the arguments to the function.
Shell Script to read given no of lines in file
#!/bin/bash
if [ $# -ne 3 ]; then
echo "Usage: $0 <filename> <start_line> <end_line>"
exit 1
fi
filename=$1
start_line=$2
end_line=$3
if [ ! -f $filename ]; then
echo "$filename does not exist"
exit 1
fi
if [ $start_line -gt $end_line ]; then
echo "Start line number must be less than or equal to end line number"
exit 1
fi
current_line=1
while read line; do
if [ $current_line -ge $start_line ] && [ $current_line -le $end_line ]; then
echo $line
fi
((current_line++))
done < $filename
How you can use the script
$ ./script.sh Test.txt 5 10This will display lines 5 through 10 of Test.txt. If the file doesn’t exist, or the start line number is greater than the end line number, the script will exit with an error message.
Test.txt file
Linux is a free and open-source operating system. It was first released in 1991 by Linus Torvalds. It is based on the Unix operating system. It is widely used for servers, supercomputers and more. Linux provides a stable, secure, and customizable platform. Designed to work well with a wide range of hardware and software.
Output
~/Assignment$ bash main.sh
Usage: main.sh <filename> <start_line> <end_line>
~/Assignment$ bash main.sh Test 1 4
test does not exist
~/Assignment$ bash main.sh Test.txt 1 4
Linux is a free and open-source operating system.
It was first released in 1991 by Linus Torvalds.
It is based on the Unix operating system.
It is widely used for servers, supercomputers and more.
~/Assignment$ bash main.sh Test.txt 6 4
Start line number must be less than or equal to end line number
~/Assignment$ bash main.sh Test.txt 6
Usage: main.sh <filename> <start_line> <end_line>
~/Assignment$ bash main.sh book.txt 6 10
book.txt does not exist
~/Assignment$ Thank you for reading, If you have reached so far, please like the article, It will encourage me to write more such articles. Do share your valuable suggestions, I appreciate your honest feedback!
