How to produce a file by many files?

Shell Programming and Scripting
1

i got these files:

files: Prac1, Prac2, Prac3 (these 3 files have the same format), the format :
Prac1
20693680 10
20179687 9
20781637 5
21907894 6

Prac2
20693680 8
20179687 6
21907894 2

Prac3
20693680 8
21907894 9

file STUDENTS, the format:
20693680:familyname, firstname
20179687:familyname, firstname
20781637:familyname, firstname
21907894:familyname, firstname

How can i use these files to produce a file called MISSING that this file is finding out which ID number has miss out the prac in the file Prac1, Prac2 and Prac3? Using bourne shell script.

Output file called Missing:

20179687 Prac3
20781637 Prac2, Prac3

i am thinking of this

cat Students | while read Student_ID
for num in 1 2 3 #which is for Prac 1, Prac2 and Prac3
    # for line in (length of file)
    #while any line match with the Student_id
    #then print nothing
    #else print the Student_ID: Prac 1 or i ??
    #if there is a Prac after the Student_id
    #then need a , and then print the second one and third one
    #to a file called Missing
done

Can anyone please help me with this question?

2

what have you tried so far?

3

i still think of which files should i need for it. i am stuck on it. can you please help?

4

can anyone help me with this question?

5

Can you paste the actual output you are expecting from the above 3 files? This will help us design the solution for you.

cheers,
Devaraj Takhellambam

6

Output file called Missing:

20179687 Prac2
20781637 Prac2, Prac3
7

20179687 doesn't seem to be present in prac3 also. How is this file derived from the above files

8

yea the file missing is showing who is missing in the file, 20179687 is missing in the file Prac 3, so i need to print it to the file missing.

9

oooo sorry i make wrong

20179687 Prac3
20781637 Prac2, Prac3

10

can anyone please help me??

Thank you....

11

i got something like this:

#!/bin/sh

cat Students |while read Student_ID
do 
	for(i=1; i -le 3; i++)
	cat Prac$i |while read ID
		if [ Student_ID -ne ID ]
		then
			if [Student_ID exist in file Missing]
			then
			echo ", Prac$i" >>Missing
			else
			echo "Student_ID: Prac$i" >>Missing
			fi
		fi
done

but it is not working, can someone please change it for me and how can i add things at the end of each line??
Thank you