Nested for loop in unix shell scripting

Question

I have two variables named A and B for files subject and Scores like below

A=contents of file 'subject' which contains "English Hindi Telugu"

B=contents of file 'Scores' which contains "60 60 10"

i want to tag the subject with marks in respective way i.e

english ==> 60 hindi ==> 60 telugu ===>10

i implemented as below but its showing weird results:

English ==> 60 English ==> 60 English ==> 10 Hindi ==> 60 
Hindi ==> 60 Hindi ==> 10 Telugu ==> 60 Telugu ==> 60 Telugu ==> 10

I want the results to be like below English ==> 60 Hindi ==> 60 Telugu ==> 10

#!/bin/ksh
A=`cat subject`
B=`cat Scores`
for sub in $A
do
   for score in $B
   do
    echo " $sub ==> $score "
   done
done

Possible duplicate of Reading lines from two files in one while loop — tripleee
– tripleee, Commented Oct 12, 2016 at 9:12
A nested loop necessarily repeats the inner loop for every iteration of the outer loop. That's clearly not what you want; you should clarify the title. — tripleee
– tripleee, Commented Oct 12, 2016 at 9:14

Jens · Accepted Answer · 2016-10-12 11:30:36Z

2

This would be somewhat easier if the words in the files appeared on separate lines, such as

$ cat subject
English
Hindi
Telugu
$ cat Scores
60
60
10

Then use some nifty Unix philosophy:

$ paste subject Scores | sed 's/\t/ ==> /'
English ==> 60
Hindi ==> 60
Telugu ==> 10

The paste utility takes care of opening multiple files and reading them line by line, in sync.

To convert your original files, use something like this:

$ printf '%s\n' $(cat subject)
English
Hindi
Telugu

edited Oct 12, 2016 at 11:30

answered Oct 12, 2016 at 9:13

Jens

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1 Comment

tripleee Over a year ago

Or just tr ' ' '\n' <subject and similarly for Scores

Inian · Accepted Answer · 2016-10-12 09:09:56Z

1

Am not sure what is your actual use-case doing this, but you can define two file-descriptors and read it together and print them together using printf

#!/bin/bash

while IFS= read -r subjectVal <&4 && IFS= read -r scoreVal <&3; do
    printf "%s%s\t" "$subjectVal"" ==> ""$scoreVal"   # To have them all in a single-line
  # printf "%s%s\n" "$subjectVal"" ==> ""$scoreVal"   # To print them in new-lines
done 4<subject 3<scores

printf "\n"

Running the script as ./script.sh would produce an output something like:-

English ==> 60  Hindi ==> 60    Telugu ==> 10

answered Oct 12, 2016 at 9:09

Inian

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