CODEWITHSUNDEEP
shell
user3137879
user3137879

Reputation: 63

reading a file in shell scripting

i want to read a file and print it on the screen by shell scripting , so i have find a simple code to do this :

#! /bin/bash 

FILENAME=$1
Lines=$(wc -l < $FILENAME)

count=0

while [ $count -lt $Lines ]
do
    let count++
    LINE= `head -n $count $FILENAME | tail -1 `
    echo "$count $LINE"
done
echo -e "\nTotal $count lines read"

, but i'm didn't understand the following line : 

LINE= `head -n $count $FILENAME | tail -1 `

any help ??

Upvotes: 1

Views: 237

Answers (4)

Hakkim Ansari K
Hakkim Ansari K

Reputation: 9

the following simple script will help

readfile.sh

file=$1

cat $file | while read line
do
    echo $line
done

Reading file into an array,

readfileAsArray.sh

file=$1

let index=1

while IFS=$'\n' read -r -a myArray
do
    file_content_array[$index]="${myArray[0]}"
    echo ${file_content_array[$index]}
    let index=$index+1
done < $file

Upvotes: 0

glenn jackman
glenn jackman

Reputation: 246744

Very inefficient as others have pointed out. @devnull's observation cat -n file is spot on.

To emulate that in bash, I'd write:

declare -i linenum=0
while IFS= read -r line; do
    printf "%8d  %s\n" $((linenum++)) "$line"
done < file

Upvotes: 1

devnull
devnull

Reputation: 123448

The line

LINE= `head -n $count $FILENAME | tail -1 `

doesn't do what you think it should. It tries to execute the command produced by the output of

head -n $count $FILENAME | tail -1

with a variable LINE (without a value) passed to it.

Instead say:

LINE=$(head -n $count $FILENAME | tail -1)

which would essentially give the line number count in the file.

As an alternate, you could say:

LINE=$(sed -n ${count}'p' $FILENAME)

to get the line.

Your script seems to be emulating

cat -n filename

Upvotes: 1

Oliver Matthews
Oliver Matthews

Reputation: 7803

This will first run head on the file, taking the first $count lines of the file. It is then piped (|) into tail, which (due to the -1) will return only the last line of the output of head (i.e. the countth line).

This will then get assigned to the LINE variable for processing

It's worth noting that this approach will work, but it is very inefficient.

Upvotes: 1

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