Single line backups with find or cat and xargs, etc

UNIX for Beginners Q & A
1

Hi, I'm new here and this is my first post. I used command line Unix at work for 3 years... about 10 years ago! Now I can't figure out nor hunt down examples of how to do the following:
Say I built a list of file to backup like this:

find ~ -name "*.pdf" -print >> MYPDF.txt

So I am using find with a redirection operator to a plain text file. Now I want to say... cat that file and pipe it to xargs using the cp command to copy them all to a single directory so I can tar them into a tar ball... but I am screwing it up!!

mkdir NEW_PDF_DIR
cat MYPDF.txt | xargs cp NEW_PDF_DIR

then I want to do something like:

tar  -cfv PDF_ARC ./NEW_PDF_DIR

Several things going on here... trying to find to build a list to use to create a tar archive... more or less. And hey, if there is an easier/smarter way to do it, Thank you all! (I figure it can be done in 1 line at the shell prompt... but hey I am re-acquiring skills here!)

2

You might consider using something like this:

find find ~ -name "*.pdf" -exec  /your/script/or/command/here.sh {} \;

Example (not your entire solution)

find find ~ -name "*.pdf" -exec  cp {}  /new/directory \;

Anyway, I normally use -exec for these tasks with find and rarely (if ever) use xargs these days.

Hope this helps.

3

You you don't say what OS you are using some GNU options can make this task easier. If cp implementations the cp -t DIRECTORY SOURCE ... method, then this makes xargs much easier to work with:

mkdir NEW_PDF_DIR
cat MYPDF.txt | xargs --no-run-if-empty cp -t NEW_PDF_DIR

Also GNU xargs allows a --no-run-if-empty which to avoids invoking cp if no files exist to be copied.

If NEW_PDF_DIR is under your home directory, you will want to prune it to avoid trying to backup the backup files!

find ~ -path ~/NEW_PDF_DIR -prune -type f -o -name "*.pdf" -print >> MYPDF.txt
4

The cp -t does the trick here, because you have the target directory first.
Both xargs and find -exec want constant arguments first.

find ~ -name "*.pdf" -exec  cp -t /new/directory {} +

Normally the cp has the target directory last. But only a few find versions allow

find ~ -name "*.pdf" -exec  cp {} /new/directory \;

or

find ~ -name "*.pdf" -exec  cp {} /new/directory +
5

Does your tar version offer the -T option? man tar :

If yes, try

find . -iname  "*.pdf" | tar cvf PDF_ARC -T-

tar also handles

  • should you have file names with LF chars.
6

A long time ago I used find ... cpio to create tar archives. As it's a long time ago I can't find any examples, but using the GNU CPIO man page and evidence of how I used to copy directories with cpio (now I use rsync ) it would have been something like this:

find -depth -name 'pattern' -print | cpio --create --format=tar > archive.tar

A SysV version would probably be more like:

find -depth -name 'pattern' -print | cpio -o -H tar > archive.tar

Of course, this was in the days when you couldn't pipe find into tar to list the files you wanted to archive...

Andrew

7

I or we used SysV Unix flavor and I am not sure if 'find' had 'exec' or not but I never used it. I use Linux (Ubuntu) now but thankfully Bash tolerates me dropping back to SysV type stuff. I want to get my SysV chops back then migrate forward into the brave new world, LOL.
Also I will use the code wrapper from now own when notating code like...

rm -rf /*

Wait, holy ... kidding. Oh, I also related to the cpio example... did that too.
Thank you all again!!