chmod Shortcuts

Let’s say we have these files:

-rwxrwxrwx  joe  acctg  wordmatic
-r--r--r--  joe  acctg  calcmatic

We’d like to remove write permission for the group and others on wordmatic, and add write and execute permission for all users on calcmatic.

Rather than try to figure out what the new permissions are and do these commands:

   chmod go=rx wordmatic
   chmod a=rwx calcmatic

The chmod command literally lets us add and subtract permissions from an existing set by using + or - instead of =.

Thus, we can take away the first file’s write permission for the group and others with this command:

   chmod go-w wordmatic

...and we can add write and execute permission to the second file for all users with:

   chmod a+wx calcmatic