M.2 Compare Replace

The AWS sync command relies upon time stamps to determine whether two programs are identical or not, as well as content. If two otherwise identical files have different time stamps, sync will assume they are different and will process the newer. However, the texinfo makeinfo --html command produces all new files even if some files (or most files) remain unchanged. This means that all files will be uploaded to the AWS S3 bucket on every iteration, even though the majority of the files are actually unchanged.

The cmprpl source code attempts to resolve the issue of identical exported code having different time stamps, thus defeating the benefit provided by the aws2 s3 sync command uploading only changed files.

This program makes sure that a generated HTML directory exists: ‘$DIR_NEW’. If it doesn’t, then it is in an improper state and the program stops with an error message.

The program then checks if an old directory exists, ‘$DIR_OLD’. If one doesn’t, then one is created by copying the current new directory. This provides a baseline for comparisons going forward. The program exits at that point. It is very important that the ‘$DIR_OLD’ directory not be deleted going forward.

Given that ‘$DIR_OLD’ exists, the program then loops through all files in ‘$DIR_NEW’ and compares them to the files in ‘$DIR_OLD’. If the files are identical, the ‘$DIR_OLD’ file replaces the ‘$DIR_NEW’ file while retaining the old time stamp (using the -p option of cp. If a file is different, then the ‘$DIR_NEW’ file replaces the ‘$DIR_OLD’ file, thus giving it updated content and an updated time stamp. If the file does not exist in the ‘$DIR_OLD’ directory, then it is added.

The program then loops through all of the files in the old directory and deletes any that do not exist in the new directory. Now both directories should be in sync.

[[ $# -eq 2 ]] || { echo "ERROR: Incorrect command line arguments"; exit 1; }
DIR_NEW=$1
DIR_OLD=$2

[[ -d $DIR_NEW ]] || { echo "ERROR: $DIR_NEW does not exist"; exit 1; }
[[ -d $DIR_OLD ]] || { echo "CREATING: $DIR_OLD does not exist"; cp -a $DIR_NEW $DIR_OLD; exit 0; }

for newfile in $DIR_NEW/*
do
    oldfile=$DIR_OLD/$(basename $newfile)
    if [[ -e $oldfile ]]
    then
       if cmp -s $newfile $oldfile
       then
           printf "${GREEN}copying OLD to NEW${CLEAR}: "
           cp -vp $oldfile $newfile
       else
           printf "${PURPLE}copying NEW to OLD${CLEAR}: "
           cp -vp $newfile $oldfile
       fi
    else
        printf "${BLUE}creating NEW in OLD${CLEAR}: "
        cp -vp $newfile $oldfile
    fi
done

for oldfile in $DIR_OLD/*
do
    newfile=$DIR_NEW/$(basename $oldfile)
    if [[ ! -e $newfile ]]
    then
        printf "${RED}removing OLD${CLEAR}: "
        rm -v $oldfile
    fi
done