Reading a file into array

Shell Programming and Scripting
1

Hi,

I need to read a file into array and print them in a loop:-
1st file :-cat a.txt
RC1
RC2
RC3
RC4

My Program:-

#!/bin/ksh
index=0
while [ $index -lt 5 ]
do
       read cnt[index]<a.txt
       print "cnt [$index] value is ${cnt[index]}
       index=`expr $index + 1`
done

Result expected :-

cnt[0] value is RC1
cnt[1] value is RC2
cnt[2] value is RC3
cnt[3] value is RC4

But i am getting the below result :-

cnt[0] value is RC1
cnt[1] value is RC1
cnt[2] value is RC1
cnt[3] value is RC1

I think there is a problem the way i am reading the file into the array

2

<a.txt will reopen the file every single time, and give you the same line every time. What you want is more like

while read ARR[index]
do
        let index=index+1
done < filename

But first I must ask, why are you reading a whole file into an array? Array sizes are not unlimited, and there's usually no need to do so anyway.

3

Try also

cnt=($(tr '\n' ' ' <file))
echo ${#cnt[@]}
4
echo ${cnt[@]}
RC1 RC2 RC3 RC4
4

Thanks corona688

i have this code and it is working fine.
Actual issue is to read input from 2 files by line wise and print them as below:-

>cat a.txt 
RC1
RC2
RC3
RC4
>cat b.txt
11
22
33
44

Desired output :-

RC1 - 11
RC2 - 22
RC3 - 33
RC4 - 44

If i am using passing of file method,i could not arrive that the desired output .so i am trying other ways .Can you help me if it can be achieved in another method.

Thanks again !!

5

Lots of ways, actually, none of which mean slurping entire whole files into memory(usually a mistake).

paste -d "-" file1 file2

exec 5<file1 # Open into FD 5
exec 6<file2 # Open into FD 6

while read A<&5 && read b<&6 # Read from FD 5 and 6
do
        echo "$A - $B"
done

exec 5<&- # Close FD 5
exec 6<&- # Close FD 6
6

Thanks Corona688 !!
You made it so simple