directory listing is showing “+” sign

Question

In one of my directory listing I get following output

drwxrws---+ 7 sip sip 4096 Aug 5 13:25 USSDG

I am the member of the group sip but I am not able to create any file if I access this directory using my user name.Can anyone point our any issue with this. Though I am specially concerned with this "+" sign which comes in last of it.I feel that this has something to do with this only.can anyone please help me understanding the usage of "+" sign.

Answer 1

Access control lists (ACL) are indicated by the +. man getfacl is usually a good point to start reading.

Answer 2

Welcome to the wonderful new Unix world of 1989!

Those nice TRUSIX people have — just this year — defined an extension to the ls command to indicate visually when the rwxrwxrwx permissions information is not actually the whole of the story. That extension is a + character following the permission flags. As you can see, your ls output has this very + character. That means that your files have these new-fangled discretionary access control list thingies that the TRUSIX people are so excited about. As such, your access to the files is not necessarily what you can deduce from the nine permissions flags alone.

To compensate for these limitations of old-style Unix tools in the face of the new-style ACLs, the TRUSIX people have also come up with a couple of new commands, getacl and setacl. The former is used for looking at those ACLs. I hear murmurings that people might prefer getfacl and setfacl as names.

In 20 years time, of course, nine bits of permissions will seem old-hat and passé, ACLs will be the norm, and even lookalike operating systems of the 1990s to come will have followed where Unix has gone before. ☺

Further reading

• Craig Rubin (1989-08-18). Rationale for Selecting Access Control List Features for the Unix System. NCSC-TG-020-A. DIANE Publishing. ISBN 9780788105548.