Clone ownership and permissions from another file?

Question

Is there a command or flag to clone the user/group ownership and permissions on a file from another file? To make the perms and ownership exactly those of another file?

Solution 1

On GNU/Linux chown and chmod have a --reference option

chown --reference=otherfile thisfile
chmod --reference=otherfile thisfile

Solution 2

On any unix with GNU utilities, such as (non-embedded) Linux or Cygwin, you can use chmod --reference and chown --reference.

If your system has ACLs, try the ACL commands getfacl and setfacl. These commands differ a little from system to system, but on many you can use getfacl other_file | setfacl -bnM - file_to_change to copy the permissions. This doesn't copy the ownership; you can do that with careful parsing of ls -l other_file, assuming that you don't have user or group names containing whitespace.

LC_ALL=C ls -l other_file | {
  read -r permissions links user group stuff;
  chown -- "$user:$group" file_to_change
}
getfacl other_file | setfacl -bnM - file_to_change

Solution 3

Did a bash command based on the response of Matteo :)

Code:

chmod $( stat -f '%p' "$1" ) "${@:2}"

Usage:

cp-permissions <from> <to>...

Solution 4

If you are not using a system with GNU's chmod/chown (which support the --reference option) you could try to parse the output of ls -l

Here a small script for chmod (if you have a see which supports extended regexes they could be written in a much more readable way ...)

#!/bin/sh

reference=$1
shift
files=$*

# strip the permissions (whith extended regexes could be more readable)
OWNER=$(ls -l ${reference} | sed -e "s/.\(...\).*/\1/"       | sed -e "s/[-]//g" )
GROUP=$(ls -l ${reference} | sed -e "s/....\(...\).*/\1/"    | sed -e "s/[-]//g" )
OTHER=$(ls -l ${reference} | sed -e "s/.......\(...\).*/\1/" | sed -e "s/[-]//g" )

chmod u=${OWNER},g=${GROUP},o=${OTHER} ${files}

UPDATE:

This is even easier using stat:

chmod $( stat -f '%p' ${reference} ) ${files}

Solution 5

This works for me:

cp -p --attributes-only <from> <to>

View more solutions

Comments

[Sohail Si]

Related questions: askubuntu.com/questions/56792/… and unix.stackexchange.com/questions/44253/…

[enzotib]

You should have ACL installed and filesystem mounted with ACL enabled.

[Gilles 'SO- stop being evil']

@enzotib At least on Linux, ACL tools will work to copy permissions (but not ownership) even if the source and target filesystem don't support ACLs.

[jfg956]

Instead of parsing ls -l output, you could you could parse statoutput.

[Matteo]

@jfgagne: thanks makes sense I do not know why I didn't think about it in the first place. I updated the answer

[Grzegorz Wierzowiecki]

Could you reference to this answer (and likely cite it) as answer to my question : unix.stackexchange.com/questions/44253/… ? , I think I will be great addition and I'd love to find up-votes there for it.

[enzotib]

@GrzegorzWierzowiecki: probably that question should be closed, but is a little bit different than this and already has answers, so I better do nothing.

[Grzegorz Wierzowiecki]

As you wish and suggest. Thanks for help, I have never put attention to --reference parameter of chmod and chown before :).

[mr.spuratic]

You're using *BSD stat syntax here. Your chmod $(stat ...) command won't work because %p alone outputs too much information for *BSD's chmod, use %Lp to output just the u/g/o bits. Something slightly more elaborate would be required for sticky/setuid/setgid bits.

[Ciro Santilli Путлер Капут 六四事]

chmod "$(stat -c '%a' "$fromfile")" tofile in GNU Coreutils, but you might as well use --reference in that case since thestat CLI utility is not POSIX, it even says pubs.opengroup.org/onlinepubs/9699919799/utilities/ls.htmlth‌​at ls -l won't cut it: "The output of ls (with the -l and related options) contains information that logically could be used by utilities such as chmod and touch to restore files to a known state. However, this information is presented in a format that cannot be used directly by those utilities or be easily translated into a format that can be used."

[Stéphane Chazelas]

That copies all attributes though (change -p to --preserve=ownership,mode to copy only permissions and ownership (and ACLs if any)). That will also not work for files of type directory. Also note that if <to> is a symlink, that will copy the attributes to the target of the symlink (likely what one would want anyway as permissions of symlinks themselves are rarely relevant (though ownership can be)).

[Vlastimil Burián]

Why not parse ls (and what to do instead)? | -1