Centos copy file into another file, if exists, create a version - linux

Question

Does anyone know of a way to (via bash) setup a "versioning" copy of a file into another? For example: I am copying file into file.bak. If file.bak exists, I am currently overwriting. What I'd like to do is set it up so that it creates multiple files: file, file.bak, file.bak.1, file.bak.2, etc...
Right now, I'm using:
cp -rf file file.bak
This currently overwrites the file(as expected)

Answer 1

or:
cp --backup=t file1 file2
repeat few times to see the result...
see https://www.gnu.org/software/coreutils/manual/html_node/cp-invocation.html

Answer 2

Simply use a test
[ -e file.bak ] && cp -r file file.bak.$(date +%s) || cp -r file file.bak
This will create a unique backup if file.bak already exists in the form file.bak.1411505497

Answer 3

There are many ways to skin this cat.
Since you're using Linux, it's likely you've got the GNU mv command, which may include a --backup option. You could wrap this in a shell function:
bkp() {
file="$1"
if [ -f "$file" ]; then
/bin/mv -v --backup=numbered "$(mktemp ${file}XXX)" "$file"
#/bin/rm "$file"
fi
}
You can put this in your .bashrc, for example. Then you can use this as follows:
# bkp foo
This will copy foo to numbered backup files. You can uncomment the rm if this is, for example, a log file that you're rotating.
Another option, which is more portable to operating systems that don't use GNU tools (i.e. FreeBSD, OSX) might be something like this quick-and-dirty solution might work:
bkp() {
file="$1"
if [ -f "$file" ]; then
# increment existing files up to 10
for n in {9..1}; do
if [ -f $file.$n ]; then
# remove -v if you want less noise.
mv -v "${file}.$n" "${file}.$[n+1]"
fi
done
# move the original to first backup position
mv "$file" "$file.1"
else
echo "Not found: $file" >&2
fi
}
It suffers in that it won't compact your list of files (and will throw errors) if some numbers are missing, but that's stuff you can add if it's important. You'd use it pretty much the same way, changing the final mv to a cp if you need to keep the original in place.
Final option I'll mention is in comments as well. Since you've said that you're using this solution to back up "system files" (which I assume you mean to be things in /etc/) you should consider using an actual version control system to control your versions of these files.
Many options exist, but I'd recommend RCS for its simplicity and low overhead. Simply install the package, mkdir /etc/RCS to keep your /etc directory clean, read the man pages for rcs, ci, co, rlog, rcsdiff and perhaps rcsintro, and you're good to go. You'll get better control of diffs and history, opportunity for comments, none of the overhead of a repository for a large VCS like SVN or Git. I've been using this on various servers for years, as RCS is still built in to the base system in FreeBSD. :)