How to loop through files in a Directory and get diff between them-CodePudding

These are my folders/files:

backup/
├── folder1
│   ├── file1.txt
│   ├── file2.txt
│   └── file3.txt
└── folder2

file1.txt (is empty) file2.txt (there is only X inside the file) file3 (last created empty)

My Script:

#!/bin/sh
#config-checker.sh

#First loop looks at each folder in backup/. 

for j in `ls backup/  -1t` 

do

    #change directory to other folders
    cd backup/${j}/
    N=0

    #Grab the two newest files. Add them to an array called FILE
    for i in `ls -1t | head -2`
    do
        FILE[$N]=$i
        N=$N 1
    done

    #diff the two files in FILE
    var=`diff ${FILE[0]} ${FILE[1]}`

    #if a diff exists, show it
    if [[ ${var} ]]
        then
        #script here takes two variables; the name of the folder and the content of the diff
        echo $j "${var}"
    fi
done

It's not getting me the diff on the file, my output is this:

./config-checker.sh: 17: FILE[0]=file2: not found ./config-checker.sh: 17: FILE[0 1]=file3: not found ./config-checker.sh: 1: Bad substitution folder1 ./config-checker.sh: 11: cd: can't cd to backup/folder2 ./config-checker.sh: 17: FILE[0]=file2: not found ./config-checker.sh: 17: FILE[0 1]=file3: not found ./config-checker.sh: 1: Bad substitution folder2

Not sure what Im missing here. Any help would be appreciated. Thank you

CodePudding user response：

Firstly - I think knittl comment is correct in stating you don't return from the cd.

Secondly - I've edited my response. If I now understand correctly, you want to walk all the sub-folders of a folder. For each sub-folder, diff the two most recent files in the sub-folder, if there are two, output the name of the first file and the diff.

For completeness I've amended my answer to what I would have written, which is not so different to your original solution:

topfolder=~/tmp/test
for folder in  $(ls -1t $topfolder)
do  
   set --  $(ls -1t  $topfolder/$folder | head -2) 
   if [ $# -ne 2 ] || diff -q $topfolder/$folder/$1 $topfolder/$folder/$2 > /dev/null
   then
       : # Do nothing
   else
       echo $1 
       diff $topfolder/$folder/$1 $topfolder/$folder/$2
   fi
done

As point of difference, I do a quick diff to find out if there is a difference. By doing so I'm avoiding saving a potentially unlimited amount of diff text in memory. Whether it is worth taking such an approach depends on factors such as the likely size of the differences and the number of executions the loop is likely to make.