While Loop - Display lines of file based on user-input

Question

I am trying to write a shell script that asks a user for number of lines they would like to display from a file and then display those lines.

I am trying to do this via the following:

#!/bin/bash 
#author = johndoe


read -p "How many lines from /c/Users/johndoe/files/helpme.sh would you like to see? " USERLINEINPUT

LINE_NUM=1

while [ $LINE_NUM -lt $USERLINEINPUT ]
do 

    echo "$LINE_NUM: $USESRLINEINPUT"
    ((LINE_NUM++))

done < /c/Users/johndoe/files/helpme.sh

This code doesn't appear to do as I'd like, please see an example below:

    $ ./linecount.sh
How many lines from /c/Users/johndoe/files/helpme.sh would you line to see? 10
1:
2:
3:
4:
5:
6:
7:
8:
9:

Hi, Suppose you enter 10, should your program print 10 lines from helpme.sh? — Abhijit Pritam Dutta
– Abhijit Pritam Dutta, Commented Feb 20, 2018 at 15:58
hi, yes it should print the line numbers from 1 to 10 and the content for each line — user3296793
– user3296793, Commented Feb 20, 2018 at 15:58

Abhijit Pritam Dutta · Accepted Answer · 2018-02-20 16:08:54Z

1

Your code does not satisfy your requirement. You need to read each line of code into a variable and print it. Your while loop is only satisfy with user input value and you are not printing the file line at all. See the correct code below and see you mistakes. Hope this will help you:-

#!/bin/bash
#author = johndoe

LINE_NUM=1
read -p "How many lines from /c/Users/johndoe/files/helpme.sh would you like to see? " USERLINEINPUT
while read -r line
do
     echo "$LINE_NUM:$line"
     if [ $LINE_NUM -ge $USERLINEINPUT ]; then
        break;
     fi
     ((LINE_NUM++))
done < "/c/Users/johndoe/files/helpme.sh"

answered Feb 20, 2018 at 16:08

Abhijit Pritam Dutta

5,6112 gold badges13 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

PesaThe · Accepted Answer · 2018-02-20 16:48:53Z

0

#!/usr/bin/env bash

# file will be the first argument or helpme.sh by default
file=${1:-/c/Users/johndoe/files/helpme.sh}    

# exit if the file is NOT readable
[[ -f $file && -r $file ]] || exit 1

# ask for a number and exit if the input is NOT a valid number
IFS= read -r -p "Number of lines from \"$file\": " num
[[ $num =~ ^[0-9]+$ ]] || exit 2

# 1st option: while/read 
count=
while IFS= read -r line && ((count++<num)); do
    printf '%d:%s\n' "$count" "$line"
done < "$file"

# 2nd option: awk
awk 'NR>ln{exit}{print NR":"$0}' ln="$num" "$file"

edited Feb 20, 2018 at 16:48

answered Feb 20, 2018 at 16:29

PesaThe

7,5791 gold badge23 silver badges47 bronze badges

Collectives™ on Stack Overflow

While Loop - Display lines of file based on user-input

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related