Backup algorithm in Bash using dry-run

Question

This is my algorithm to backup data on Windows using Bash scripting language. I'm looking forward to any innovations, and better solutions. My task was to create a simple backup algorithm using dry-run and delete. Are there any simpler solutions? Also, adding a GUI would be a pretty nice training for me, but in my case, I'm not too familiar with that.

#!/bin/bash
src=1ドル
dst=2ドル
option1=3ドル
option2=4ドル
src_files=$(ls $src)
dst_files=$(ls $dst)
files_to_copy () {
 files_to_copy=()
 for file in $src_files; do
 if [[ ! $dst_files =~ $file ]]; then
 files_to_copy+=($file)
 fi
 done
 echo ${files_to_copy[@]}
}
files_to_delete () {
 to_delete=( )
 for file in $dst_files; do
 if [[ ! $src_files =~ $file ]]; then
 to_delete+=($file)
 fi
 done
 echo ${to_delete[@]}
}
to_copy=$(files_to_copy)
if [[ "$option1" == "del" || "$option2" == "del" ]]; then
 to_delete=$(files_to_delete)
fi
dry_run () {
 for file in ${to_copy[@]}
 do
 echo cp $src/$file $dst
 done
 
 for file in ${to_delete[@]}
 do
 echo rm $dst/$file 
 done
}
run () {
 for file in ${to_copy[@]}
 do
 cp $src/$file $dst
 done
 
 for file in ${to_delete[@]}
 do
 rm $dst/$file 
 done
}
if [[ "$option1" == "dryrun" || "$option2" == "run" ]]; then
 dry_run
else
 run
fi

Thank you in advance, and have a nice day.

Answer 1

Since you're using Bash, then you can take advantage of array variables for src_files and dst_files. Definitely don't just expand $(ls) like that, because the result will be word-split according to $IFS.

Having built a neat array in files_to_copy(), we then lose all its structure by printing out and storing in a string variable.

I don't think $file is set when files_to_copy() is invoked - add set -u to make sure we don't attempt to use non-existent variables.

Instead of separate run and dry_run, we can use a variable to selectively enable 'echo' like this:

run()
{
 ${prefix+"${prefix[@]}"} cp "${to_copy[@]/#/$src/}" "$dst"
 ${prefix+"${prefix[@]}"} rm "${to_delete[@]/#/$dst/}"
}
dry_run()
{
 prefix=(echo) do_it "$@"
}

(I also simplified your loops into single commands, by substituting the directory at start of each filename, which works only if to_copy and to_delete are actually arrays of filenames).

• Marcinkiewicz: Hii, when i was trying to use your run() function i'm getting errors "cp: cannot stat '/backupv1.sh understanding_swap.sh whiptail.sh': No such file or directory rm: cannot remove 'backup/': Is a directory"
• Toby Speight: Yes. As I said that will only work once to_copy and to_delete are correctly populated as arrays of filenames. I perhaps should have made that condition more prominent!