BASH while loop to check lines in file displays too many times - bash

Question

I am writing a script where I want to take each line from a file and check for a match in another file.
If I find a match I want to say that I found a match and if not, say that I did not find a match.
The 2 files contain md5 hashes. The old file is the original and the new file is to check if there have been any changes since the original file.
original file: chksum
new file:chksum1
#!/bin/bash
while read e; do
while read f; do
if [[ $e = $f ]]
then
echo $e "is the same"
else
if [[ $e != $f]]
then
echo $e "has been changed"
fi
fi
done < chksum1
done < chksum
My issue is that for the files that have been changed I get an echo for every time the check in the loop is done and I only want it to display the file once and say that it was not found.
Hope this is clear.

Answer 1

you could use the same script but put a reminder.
#!/bin/bash
while read e; do
rem=0
while read f; do
if [[ $e = $f ]]
then
rem=1
fi
done < chksum1
if [[ rem = 1 ]]
then
echo $e "is the same"
else
echo $e "has been changed"
fi
done < chksum
This should work correctly

Answer 2

You were real close. This will work:
while read e; do
while read f; do
found=0
if [[ $e = $f ]]
then
# echo $e "is the same"
found=1
break
fi
done < chksum1
if [ $found -ne 0 ]
then
echo "$e is the the same"
else
echo "$e has been changed"
fi
done < chksum

Answer 3

A little bit simplified version which avoid the multiple read of the same file (bash 4.0 and above). I assume that the files contain unique filenames and the file format is the output of the md5sum command.
#!/bin/bash
declare -A hash
while read md5 file; do hash[$file]=$md5; done <chksum
while read md5 file; do
[ -z "${hash[$file]}" ] && echo "$file new file" && continue
[ ${hash[$file]} == $md5 ] && echo "$file is same" && continue
echo "$file has been changed"
done <chksum1
This script reads the first file to an associative array, called hash. The index is the name of the file, and the value is the MD5 checksum. The second loop reads the second checksum file; the file name is not in the hash it prints file new file; if it is in the hash and the value equals then it is the same file; if it does not equals it writes file has been changed.
Input files:
$ cat chksum
eed0fc0313f790cec0695914f1847bca ./a.txt
9ee9e1fffbb3c16357bf80c6f7a27574 ./b.txt
a91a408e113adce865cba3c580add827 ./c.txt
$ cat chksum1
eed0fc0313f790cec0695914f1847bca ./a.txt
8ee9e1fffbb3c16357bf80c6f7a27574 ./b.txt
a91a408e113adce865cba3c580add827 ./d.txt
Output:
./a.txt is same
./b.txt has been changed
./d.txt new file
EXTENDED VERSION
Also detect deleted files.
#!/bin/bash
declare -A hash
while read md5 file; do hash[$file]=$md5; done <chksum
while read md5 file; do
[ -z "${hash[$file]}" ] && echo "$file new file" && continue
if [ ${hash[$file]} == $md5 ]; then echo "$file is same"
else echo "$file has been changed"
fi
unset hash[$file]
done <chksum1
for file in ${!hash[*]};{ echo "$file deleted file";}
Output:
./a.txt is same
./b.txt has been changed
./d.txt new file
./c.txt deleted file

Answer 4

I'd like to suggest an alternate solution: How about you don't read line by line, but use sort and uniq -c to see if there are differences. There is no need for a loop where a simple pipe can do your job.
In this case you want all the lines that have changed in file chksum1, so
sort chksum chksum1 chksum1 | uniq -c | egrep '^\s+2\s' | sed 's%\s\+2\s%%'
This also reads chksum1 only 2 times, as compared to the loop based example, which reads it once per line of chksum.
Reusing the input files from one of the other answers:
samveen#precise:~/so$ cat chksum
eed0fc0313f790cec0695914f1847bca ./a.txt
9ee9e1fffbb3c16357bf80c6f7a27574 ./b.txt
a91a408e113adce865cba3c580add827 ./c.txt
samveen#precise:~/so$ cat chksum1
eed0fc0313f790cec0695914f1847bca ./a.txt
8ee9e1fffbb3c16357bf80c6f7a27574 ./b.txt
a91a408e113adce865cba3c580add827 ./d.txt
samveen#precise:~/so$ sort chksum chksum1 chksum1 |uniq -c | egrep '^\s+2\s' |sed 's%\s\+2\s%%'
8ee9e1fffbb3c16357bf80c6f7a27574 ./b.txt
a91a408e113adce865cba3c580add827 ./d.txt
Another possible solution is (as suggested in the question's comments) to use diff in conjunction with sort:
diff <(sort chksum) <(sort chksum1) |grep '^>'
The output:
samveen#precise:~/so$ diff <(sort chksum) <(sort chksum1) |grep '^>'
> 8ee9e1fffbb3c16357bf80c6f7a27574 ./b.txt
> a91a408e113adce865cba3c580add827 ./d.txt

Answer 5

Simple solution:
diff -q chksum1 chksum

Answer 6

What about using the command grep. Every line that you read from chksum will serve as a search pattern in chksum1. If grep finds a match,the "$?" which contains the return value of the grep will be equal to 0, otherwise, it will be equal to 1
while read e; do
grep $e checksum1
if[ $? == "0" ];then
echo $e "is the same"
else
echo $e "has been changed"
fi
done < chksum