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Poni
Asked: 2012-01-24 00:35:25 +0800 CST

chmod while keeping current owner/group permissions

  • 772

I use for example to change everyone's permissions:

chmod 777 file

Now, what if I want to preserve the current permissions?
I know there's something like

chmod xx7 file

in case I'd only want to change the world permissions, but I can't work it out (forgot).

Thanks!

linux permissions

2 Answers

  1. You can use the symbols o for others such as:

    chmod o+rwx file

    , 

    chmod o-rwx file

    or

    chmod o+r file

    You can use - to revoke or + to grant the permission r, x , w, or any combination of them. Similarly, you can do this for user u or group g.

    • 9

  2. Khaled's answer is best: learn to use symbols.

    If you really want something to set permissions like you want, you can write some sort of script to get the octal format of the permissions, strip off the last digit and substitute your own.

    I suppose you can write some sort of bash script like (note: untested and has no input validation):

    #!/bin/bash

otherperm=$1
filename=$2

newperm=`stat -c%a $filename  |sed -e "s/.$/$otherperm/"`

echo chmod ${newperm} ${filename}

    but, really, learn to use symbols in chmod.

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