Please explain file permissions

Raven · Posted: Tue Nov 27, 2007 1:47 am

A Brief Overview on File Permissions

0400 read by user
0200 write by user
0100 execute by user

0040 read by group
0020 write by group
0010 execute by group

0004 read by world
0002 write by world
0001 execute by world

By adding the permissions together, you will come up with the number that corresponds to the permission. For example, 400+200+100+40+20+10+4+2+1=777 - read/write/execute by user/group/world.

If you start with permissions of 644 you would see that 6=400+200 4=40 4=4. So, 6=read by user & write by user / 4=read by group / 4=read by world. Another way of writing 644 is rw-r--r--.